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| an important notice at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. production data. ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 ads1299-x low-noise, 4-, 6-, 8-channel, 24-bit, analog-to-digital converter for eeg and biopotential measurements 1 1 features 1 ? up to eight low-noise pgas and eight high- resolution simultaneous-sampling adcs ? input-referred noise: 1 v pp (70-hz bw) ? input bias current: 300 pa ? data rate: 250 sps to 16 ksps ? cmrr: ? 110 db ? programmable gain: 1, 2, 4, 6, 8, 12, or 24 ? unipolar or bipolar supplies: ? analog: 4.75 v to 5.25 v ? digital: 1.8 v to 3.6 v ? built-in bias drive amplifier, lead-off detection, test signals ? built-in oscillator ? internal or external reference ? flexible power-down, standby mode ? pin-compatible with the ads129x ? spi-compatible serial interface ? operating temperature range: ? 40 c to +85 c 2 applications ? medical instrumentation including: ? electroencephalogram (eeg) study ? fetal electrocardiography (ecg) ? sleep study monitor ? bispectral index (bis) ? evoked audio potential (eap) 3 description the ads1299-4, ads1299-6, and ads1299 devices are a family of four-, six-, and eight-channel, low- noise, 24-bit, simultaneous-sampling delta-sigma ( ) analog-to-digital converters (adcs) with a built-in programmable gain amplifier (pga), internal reference, and an onboard oscillator. the ads1299-x incorporates all commonly-required features for extracranial electroencephalogram (eeg) and electrocardiography (ecg) applications. with its high levels of integration and exceptional performance, the ads1299-x enables the creation of scalable medical instrumentation systems at significantly reduced size, power, and overall cost. the ads1299-x has a flexible input multiplexer per channel that can be independently connected to the internally-generated signals for test, temperature, and lead-off detection. additionally, any configuration of input channels can be selected for derivation of the patient bias output signal. optional srb pins are available to route a common signal to multiple inputs for a referential montage configuration . the ads1299-x operates at data rates from 250 sps to 16 ksps. lead-off detection can be implemented internal to the device using an excitation current sink or source. multiple ads1299-4, ads1299-6, or ads1299 devices can be cascaded in high channel count systems in a daisy-chain configuration. the ads1299-x is offered in a tqfp-64 package specified from ? 40 c to +85 c. device information (1) part number package body size (nom) ads1299-x tqfp (64) 10.00 mm 10.00 mm (1) for all available packages, see the orderable addendum at the end of the data sheet. block diagram control clk gpio and control oscillator spi test signals and monitors spi patient bias and reference reference ref adc7 adc8 adc1 adc2 adc3 adc4 adc5 adc6 a7 a8 a1 a2 a3 a4 a5 a6 mux inputs ?? to channel ads1299 only ads1299-6, ads1299 only productfolder sample &buy technical documents tools & software support &community
2 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated table of contents 1 features .................................................................. 1 2 applications ........................................................... 1 3 description ............................................................. 1 4 revision history ..................................................... 2 5 device comparison ............................................... 4 6 pin configuration and functions ......................... 4 7 specifications ......................................................... 6 7.1 absolute maximum ratings ...................................... 6 7.2 esd ratings .............................................................. 6 7.3 recommended operating conditions ....................... 7 7.4 thermal information .................................................. 7 7.5 electrical characteristics ........................................... 8 7.6 timing requirements: serial interface .................... 11 7.7 switching characteristics: serial interface .............. 11 7.8 typical characteristics ............................................ 12 8 parametric measurement information ............... 15 8.1 noise measurements .............................................. 15 9 detailed description ............................................ 17 9.1 overview ................................................................. 17 9.2 functional block diagram ....................................... 18 9.3 feature description ................................................. 19 9.4 device functional modes ........................................ 34 9.5 programming ........................................................... 37 9.6 register maps ......................................................... 43 10 applications and implementation ...................... 60 10.1 application information .......................................... 60 10.2 typical application ................................................ 65 11 power supply recommendations ..................... 69 11.1 power-up sequencing .......................................... 69 11.2 connecting the device to unipolar (5 v and 3.3 v) supplies ................................................................... 69 11.3 connecting the device to bipolar ( 2.5 v and 3.3 v) supplies ................................................................... 70 12 layout ................................................................... 71 12.1 layout guidelines ................................................. 71 12.2 layout guidelines ................................................. 71 12.3 layout example .................................................... 72 13 device and documentation support ................. 73 13.1 documentation support ........................................ 73 13.2 receiving notification of documentation updates 73 13.3 community resources .......................................... 73 13.4 trademarks ........................................................... 73 13.5 electrostatic discharge caution ............................ 73 13.6 glossary ................................................................ 73 14 mechanical, packaging, and orderable information ........................................................... 73 4 revision history note: page numbers for previous revisions may differ from page numbers in the current version. changes from revision a (august 2012) to revision b page ? added esd ratings table, feature description section, device functional modes , application and implementation section, power supply recommendations section, layout section, device and documentation support section, and mechanical, packaging, and orderable information section ................................................................................................. 1 ? added ads1299-4 and ads1299-6 to document .................................................................................................................. 1 ? added .................................................................................................................................................................................... 1 ? deleted low power features bullet ...................................................................................................................................... 1 ? changed extracranial electroencephalogram (eeg) in applications and description sections ............................................. 1 ? deleted last applications bullet .............................................................................................................................................. 1 ? changed description section: added sentence on srb pins, changed last sentence of second paragraph ........................ 1 ? changed ads1299 family to ads1299-x throughout document ........................................................................................... 1 ? changed block diagram: added dotted boxes ...................................................................................................................... 1 ? changed specifications for lead-off detect, frequency parameter of electrical characteristics table ................................. 9 ? added specifications for ads1299-4 and ads1299-6 in supply current (bias turned off) and power dissipation (analog supply = 5 v, bias amplifiers turned off) sections of electrical characteristics table .......................................... 10 ? changed noise measurements section ................................................................................................................................ 15 ? changed functional block diagram to show channels 5-8 not covered in ads1299-4 and channels 7-8 not covered in ads1299-6 ....................................................................................................................................................................... 18 ? changed inxp and inxn pins in figure 18 ......................................................................................................................... 19 ? changed figure 20 and figure 21 : changed 1/2 v ref to v ref ............................................................................................ 21 ? changed figure 22 : changed pgap, pgan to pgap, pgan ............................................................................................... 22 ? changed input common-mode range section: changed input common-mode range description .................................... 22 3 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated revision history (continued) ? changed differential input voltage range in the input differential dynamic range section ................................................. 23 ? changed figure 33 : mux8[2:0] = 010 on in8n, and bias_meas = 1 on biasin ............................................................. 29 ? changed first sentence of second paragraph in lead-off detection section ....................................................................... 30 ? changed ac lead-off (one time or periodic) section ........................................................................................................ 31 ? changed bias lead-off section ............................................................................................................................................ 32 ? changed title of figure 37 and power-down description in bias drive (dc bias circuit) section ........................................ 33 ? changed start opcode to start in figure 39................................................................................................................ 34 ? changed reset ( reset) section for clarity ......................................................................................................................... 35 ? changed title, first paragraph, start opcode and stop opcode to start and stop ( figure 41 ), and stop opcode to stop command ( figure 42 ) in continuous conversion mode section ............................................................. 36 ? added last sentence to data input (din) section ................................................................................................................. 39 ? added cross-reference to the sending multi-byte commands section in rdatac: read data continuous section ........ 40 ? changed rdatac opcode to rdatac in figure 45 .......................................................................................................... 40 ? changed rdata opcode to rdata in figure 46 ............................................................................................................... 41 ? changed description of sclk rate restrictions, opcode 1 and opcode 2 to byte 1 and byte 2 in figure 47 of rreg: read from register section .................................................................................................................................... 42 ? changed footnotes 1 and 2 and added more cross-references to footnotes in rows 0dh to 11h in table 11 ................... 43 ? changed register description and description of bit 5 in misc1: miscellaneous 1 register section ................................... 58 ? changed output names in figure 67 from ra , la , and rl to electrode 1 , electrode 2 , and bias electrode , respectively ........................................................................................................................................................................... 62 ? changed power-up sequencing section .............................................................................................................................. 69 changes from original (july 2012) to revision a page ? changed product column of family and ordering information table ..................................................................................... 1 4 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 5 device comparison product package options operating temperature range channels adc resolution maximum sampling rate ads1299-4 tqfp-64 ? 40 c to +85 c 4 24 16 ksps ads1299-6 tqfp-64 ? 40 c to +85 c 6 24 16 ksps ads1299 tqfp-64 ? 40 c to +85 c 8 24 16 ksps 6 pin configuration and functions pag package 64-pin tqfp top view 4847 46 45 44 43 42 41 40 39 38 37 36 35 34 33 dvddgpio4 gpio3 gpio2 dout gpio1 daisy_in sclk start clk din dgnd drdy cs reset pwdn 12 3 4 5 6 7 8 9 1011 12 13 14 15 16 in8n in8p in7n in7p in6n in6p in5n in5p in4n in4p in3n in3p in2n in2p in1n in1p reservedbiasout biasin biasinv biasref avdd avss avss avdd vcap3 avdd1 avss1 clksel dgnd dvdd dgnd srb1 2 avdd avss avdd avdd avss vrefp vrefn vcap4 nc vcap1 nc vcap2resv1 avss srb 1718 19 20 21 22 23 24 25 26 27 28 29 30 31 32 6463 62 61 60 59 58 57 56 55 54 53 52 51 50 49 5 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) set the two-state mode setting pins high to dvdd or low to dgnd through 10-k resistors. (2) connect unused analog inputs directly to avdd. pin functions pin type description name no. avdd 19, 21, 22, 56, 59 supply analog supply. connect a 1- f capacitor to avss. 59 supply charge pump analog supply. connect a 1- f capacitor to avss, pin 58. avdd1 54 supply analog supply. connect a 1- f capacitor to avss1. avss 20, 23, 32, 57 supply analog ground 58 supply analog ground for charge pump avss1 53 supply analog ground biasin 62 analog input bias drive input to mux biasinv 61 analog input/output bias drive inverting input biasout 63 analog output bias drive output biasref 60 analog input bias drive noninverting input cs 39 digital input chip select, active low clk 37 digital input master clock input clksel 52 digital input master clock select (1) daisy_in 41 digital input daisy-chain input dgnd 33, 49, 51 supply digital ground din 34 digital input serial data input dout 43 digital output serial data output drdy 47 digital output data ready, active low dvdd 48, 50 supply digital power supply. connect a 1- f capacitor to dgnd. gpio1 42 digital input/output general-purpose input/output pin 1. connect to dgnd with a 10-k resistor if unused. gpio2 44 digital input/output general-purpose input/output pin 2. connect to dgnd with a 10-k resistor if unused. gpio3 45 digital input/output general-purpose input/output pin 3. connect to dgnd with a 10-k resistor if unused. gpio4 46 digital input/output general-purpose input/output pin 4. connect to dgnd with a 10-k resistor if unused. in1n 15 analog input differential analog negative input 1 (2) in1p 16 analog input differential analog positive input 1 (2) in2n 13 analog input differential analog negative input 2 (2) in2p 14 analog input differential analog positive input 2 (2) in3n 11 analog input differential analog negative input 3 (2) in3p 12 analog input differential analog positive input 3 (2) in4n 9 analog input differential analog negative input 4 (2) in4p 10 analog input differential analog positive input 4 (2) in5n 7 analog input differential analog negative input 5 (2) (ads1299-6 and ads1299 only) in5p 8 analog input differential analog positive input 5 (2) (ads1299-6 and ads1299 only) in6n 5 analog input differential analog negative input 6 (2) (ads1299-6 and ads1299 only) in6p 6 analog input differential analog positive input 6 (2) (ads1299-6 and ads1299 only) in7n 3 analog input differential analog negative input 7 (2) (ads1299 only) in7p 4 analog input differential analog positive input 7 (2) (ads1299 only) in8n 1 analog input differential analog negative input 8 (2) (ads1299 only) in8p 2 analog input differential analog positive input 8 (2) (ads1299 only) nc 27, 29 ? no connection, leave as open circuit reserved 64 analog output reserved for future use, leave as open circuit reset 36 digital input system reset, active low resv1 31 digital input reserved for future use, connect directly to dgnd sclk 40 digital input serial clock input srb1 17 analog input/output patient stimulus, reference, and bias signal 1 srb2 18 analog input/output patient stimulus, reference, and bias signal 2 6 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated pin functions (continued) pin type description name no. start 38 digital input synchronization signal to start or restart a conversion pwdn 35 digital input power-down, active low vcap1 28 analog output analog bypass capacitor pin. connect a 100- f capacitor to avss. vcap2 30 analog output analog bypass capacitor pin. connect a 1- f capacitor to avss. vcap3 55 analog output analog bypass capacitor pin. connect a parallel combination of 1- f and 0.1- f capacitors to avss. vcap4 26 analog output analog bypass capacitor pin. connect a 1- f capacitor to avss. vrefn 25 analog input negative analog reference voltage. vrefp 24 analog input/output positive analog reference voltage. connect a minimum 10- f capacitor to vrefn. (1) stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions . exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. (2) input pins are diode-clamped to the power-supply rails. limit the input current to 10 ma or less if the analog input voltage exceeds avdd + 0.3 v or is less than avss ? 0.3 v, or if the digital input voltage exceeds dvdd + 0.3 v or is less than dgnd ? 0.3 v. 7 specifications 7.1 absolute maximum ratings (1) min max unit voltage avdd to avss ? 0.3 5.5 v dvdd to dgnd ? 0.3 3.9 avss to dgnd ? 3 0.2 vrefp to avss ? 0.3 avdd + 0.3 vrefn to avss ? 0.3 avdd + 0.3 analog input avss ? 0.3 avdd + 0.3 digital input dgnd ? 0.3 dvdd + 0.3 current input, continuous, any pin except power supply pins (2) ? 10 10 ma temperature maximum junction, t j 150 c storage, t stg ? 60 150 (1) jedec document jep155 states that 500-v hbm allows safe manufacturing with a standard esd control process. (2) jedec document jep157 states that 250-v cdm allows safe manufacturing with a standard esd control process. 7.2 esd ratings value unit v (esd) electrostatic discharge human-body model (hbm), per ansi/esda/jedec js-001 (1) 1000 v charged-device model (cdm), per jedec specification jesd22-c101 (2) 500 7 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 7.3 recommended operating conditions over operating free-air temperature range (unless otherwise noted) min nom max unit power supply analog power supply avdd to avss 4.75 5 5.25 v digital power supply dvdd to dgnd 1.8 1.8 3.6 v analog to digital supply avdd ? dvdd ? 2.1 3.6 v analog inputs full-scale differential input voltage v inxp ? v inxn v ref / gain v input common-mode range (v inxp + v inxn ) / 2 see the input common-mode range subsection of the pga settings and input range section voltage reference inputs v ref reference input voltage v ref = (v vrefp ? v vrefn ) 4.5 v vrefn negative input avss v vrefp positive input avss + 4.5 v clock input external clock input frequency clksel pin = 0 1.5 2.048 2.25 mhz digital inputs input voltage dgnd dvdd v temperature range t a operating temperature range ? 40 85 c (1) for more information about traditional and new thermal metrics, see the semiconductor and ic package thermal metrics application report. 7.4 thermal information thermal metric (1) ads1299-4, ads1299-6, ads1299 unit pag (tqfp) 64 pins r ja junction-to-ambient thermal resistance 46.2 c/w r jc(top) junction-to-case (top) thermal resistance 5.8 c/w r jb junction-to-board thermal resistance 19.6 c/w jt junction-to-top characterization parameter 0.2 c/w jb junction-to-board characterization parameter 19.2 c/w r jc(bot) junction-to-case (bottom) thermal resistance n/a c/w 8 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) noise data measured in a 10-second interval. test not performed in production. input-referred noise is calculated with the input shorted (without electrode resistance) over a 10-second interval. (2) cmrr is measured with a common-mode signal of avss + 0.3 v to avdd ? 0.3 v. the values indicated are the minimum of the eight channels. 7.5 electrical characteristics minimum and maximum specifications apply from ? 40 c to 85 c. typical specifications are at +25 c. all specifications are at dvdd = 3.3 v, avdd ? avss = 5 v, v ref = 4.5 v, external f clk = 2.048 mhz, data rate = 250 sps, and gain = 12, unless otherwise noted. parameter test conditions min typ max unit analog inputs input capacitance 20 pf input bias current t a = +25 c, input = 2.5 v 300 pa t a = ? 40 c to +85 c, input = 2.5 v 300 dc input impedance no lead-off 1000 m ? current source lead-off detection (i leadoff = 6 na) 500 pga performance gain settings 1, 2, 4, 6, 8, 12, 24 bw bandwidth see table 5 adc performance resolution 24 bits dr data rate f clk = 2.048 mhz 250 16000 sps dc channel performance input-referred noise (0.01 hz to 70 hz) 10 seconds of data, gain = 24 (1) 1 v pp 250 points, 1 second of data, gain = 24, t a = +25 c 1 1.35 250 points, 1 second of data, gain = 24, t a = ? 40 c to +85 c 1 1.6 all other sample rates and gain settings see noise measurements inl integral nonlinearity full-scale with gain = 12, best fit 8 ppm offset error 60 v offset error drift 80 nv/ c gain error excluding voltage reference error 0.1 0.5 % of fs gain drift excluding voltage reference drift 3 ppm/ c gain match between channels 0.2 % of fs ac channel performance cmrr common-mode rejection ratio f cm = 50 hz and 60 hz (2) ? 110 ? 120 db psrr power-supply rejection ratio f ps = 50 hz and 60 hz 96 db crosstalk f in = 50 hz and 60 hz ? 110 db snr signal-to-noise ratio v in = ? 2 dbfs, f in = 10-hz input, gain = 12 121 db thd total harmonic distortion v in = ? 0.5 dbfs, f in = 10 hz ? 99 db patient bias amplifier integrated noise bw = 150 hz 2 v rms gain bandwidth product 50-k ? || 10-pf load, gain = 1 100 khz slew rate 50-k ? || 10-pf load, gain = 1 0.07 v/ s thd total harmonic distortion f in = 10 hz, gain = 1 ? 80 db common-mode input range avss + 0.3 avdd ? 0.3 v short-circuit current 1.1 ma quiescent power consumption 20 a 9 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated electrical characteristics (continued) minimum and maximum specifications apply from ? 40 c to 85 c. typical specifications are at +25 c. all specifications are at dvdd = 3.3 v, avdd ? avss = 5 v, v ref = 4.5 v, external f clk = 2.048 mhz, data rate = 250 sps, and gain = 12, unless otherwise noted. parameter test conditions min typ max unit lead-off detect frequency continuous at dc, f dr / 4, see register maps for settings hz one time or periodic 7.8, 31.2 current ilead_off[1:0] = 00 6 na ilead_off[1:0] = 01 24 ilead_off[1:0] = 10 6 a ilead_off[1:0] = 11 24 current accuracy 20% comparator threshold accuracy 30 mv external reference input impedance 5.6 k ? internal reference v ref internal reference voltage 4.5 v v ref accuracy 0.2% drift t a = ? 40 c to +85 c 35 ppm start-up time 150 ms system monitors reading error analog supply 2% digital supply 2% device wake up from power-up to drdy low 150 ms standby mode 31.25 s temperature sensor reading voltage t a = +25 c 145 mv coefficient 490 v/ c test signal signal frequency see register maps section for settings f clk / 2 21 , f clk / 2 20 hz signal voltage see register maps section for settings 1, 2 mv accuracy 2% clock internal oscillator clock frequency nominal frequency 2.048 mhz internal clock accuracy t a = +25 c 0.5% ? 40 c t a +85 c 2.5% internal oscillator start-up time 20 s internal oscillator power consumption 120 w digital input/output (dvdd = 1.8 v to 3.6 v) v ih high-level input voltage 0.8 dvdd dvdd + 0.1 v v il low-level input voltage ? 0.1 0.2 dvdd v v oh high-level output voltage i oh = ? 500 a 0.9 dvdd v v ol low-level output voltage i ol = +500 a 0.1 dvdd v input current 0 v < v digitalinput < dvdd ? 10 10 a 10 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated electrical characteristics (continued) minimum and maximum specifications apply from ? 40 c to 85 c. typical specifications are at +25 c. all specifications are at dvdd = 3.3 v, avdd ? avss = 5 v, v ref = 4.5 v, external f clk = 2.048 mhz, data rate = 250 sps, and gain = 12, unless otherwise noted. parameter test conditions min typ max unit supply current (bias turned off) i avdd avdd current (normal mode) ads1299-4 avdd ? avss = 5 v 4.06 ma ads1299-6 5.57 ads1299 7.14 i dvdd dvdd current (normal mode) ads1299-4 dvdd = 3.3 v 0.54 ma ads1299-6 0.66 ads1299 1 ads1299-4 dvdd = 1.8 v 0.27 ads1299-6 0.34 ads1299 0.5 power dissipation (analog supply = 5 v, bias amplifiers turned off) quiescent power dissipation ads1299-4 normal mode 22 24 mw power-down 10 w standby mode, internal reference 5.1 mw ads1299-6 normal mode 30 33 mw power-down 10 w standby mode, internal reference 5.1 mw ads1299 normal mode 39 42 mw power-down 10 w standby mode, internal reference 5.1 mw 11 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 7.6 timing requirements: serial interface over operating free-air temperature range (unless otherwise noted) 2.7 v dvdd 3.6 v 1.8 v dvdd 2.0 v unit min max min max t clk master clock period 414 666 414 666 ns t cssc delay time, cs low to first sclk 6 17 ns t sclk sclk period 50 66.6 ns t spwh, l pulse duration, sclk pulse duration, high or low 15 25 ns t dist setup time, din valid to sclk falling edge 10 10 ns t dihd hold time, valid din after sclk falling edge 10 11 ns t csh pulse duration, cs high 2 2 t clk t sccs delay time, final sclk falling edge to cs high 4 4 t clk t sdecode command decode time 4 4 t clk t disck2st setup time, daisy_in valid to sclk rising edge 10 10 ns t disck2ht hold time, daisy_in valid after sclk rising edge 10 10 ns 7.7 switching characteristics: serial interface over operating ambient temperature range (unless otherwise noted) parameter 2.7 v dvdd 3.6 v 1.8 v dvdd 2.0 v unit min max min max t dohd hold time, sclk falling edge to invalid dout 10 10 ns t dopd propagation delay time, sclk rising edge to dout valid 17 32 ns t csdod propagation delay time, cs low to dout driven 10 20 ns t csdoz propagation delay time, cs high to dout hi-z 10 20 ns note: spi settings are cpol = 0 and cpha = 1. figure 1. serial interface timing figure 2. daisy-chain interface timing d isy_in a dout sclk msb d1 t disck2st msb 2 1 3 216 217 218 msb d1 lsb t disck2ht lsb d1 219 1 cs sclk din dout 2 3 8 1 2 8 3 t cssc t dist t dihd t dohd t csh t dopd t spwh t spwl t sccs hi-z t csdoz t csdod hi-z t sclk t sdecode clk t clk 12 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 7.8 typical characteristics at t a = 25 c, avdd = 5 v, avss = 0 v, dvdd = 3.3 v, internal vrefp = 4.5 v, vrefn = avss, external clock = 2.048 mhz, data rate = 250 sps, and gain = 12 (unless otherwise noted) figure 3. input-referred noise figure 4. noise histogram figure 5. common-mode rejection ratio vs frequency figure 6. leakage current vs input voltage figure 7. leakage current vs temperature figure 8. psrr vs frequency 80 85 90 95 100 105 110 115 120 10 100 1000 frequency (hz) power?supply rejection ratio (db) g = 1g = 2 g = 4 g = 6g = 8 g = 12 g = 24 g008 ?135 ?130 ?125 ?120 ?115 ?110 ?105 ?100 10 100 1000 frequency (hz) cmrr (db) gain = 1gain = 2 gain = 4 gain = 6 gain = 8 gain = 12 gain = 24 data rate = 4 kspsa in = avdd ? 0.3 v to avss + 0.3 v g005 0 50 100 150 200 250 300 350 400 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 input voltage (v) input leakage current (pa) data rate = 250 sps to 8 ksps data rate = 16 ksps g006 ?0.5?0.4 ?0.3 ?0.2 ?0.1 0 0.10.2 0.3 0.4 0.5 ?0.5?0.4 ?0.3 ?0.2 ?0.1 0 0.10.2 0.3 0.4 0.5 0 100 200 300 400 500 600 700 800 input?referred noise (v) occurences gain = 24 g004 ?0.5 ?0.4 ?0.3 ?0.2 ?0.1 0 0.1 0.2 0.3 0.4 0.5 1 2 3 4 5 6 7 8 9 10 time (s) input?referred noise (v) gain = 24 g003 0 25 50 75 100 125 150 175 200 ?40 ?30 ?20 ?10 0 10 20 30 40 50 60 70 80 90 temperature (c) leakage current (pa) input voltage = 2.5 vdata rate = 250 sps to 8 ksps g007 13 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated typical characteristics (continued) at t a = 25 c, avdd = 5 v, avss = 0 v, dvdd = 3.3 v, internal vrefp = 4.5 v, vrefn = avss, external clock = 2.048 mhz, data rate = 250 sps, and gain = 12 (unless otherwise noted) figure 9. thd vs frequency figure 10. inl vs pga gain figure 11. inl vs temperature figure 12. thd fft plot (60-hz signal) figure 13. fft plot (60-hz signal) figure 14. offset vs pga gain (absolute value) ?180 ?160 ?140 ?120 ?100 ?80 ?60 ?40 ?20 0 0 2000 4000 6000 8000 frequency (hz) amplitude (dbfs) pga gain = 12thd = ?94 db snr = 101 db data rate = 16 ksps g013 0 100 200 300 400 500 600 1 10 30 pga gain offset (v) g014 ?10 ?8 ?6 ?4 ?2 0 2 4 6 8 ?1 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1 input range (normalized to full?scale) integral nonlinearity (ppm) +25c?40c +85c gain = 12 g011 ?180 ?160 ?140 ?120 ?100 ?80 ?60 ?40 ?20 0 0 50 100 150 200 250 frequency (hz) amplitude (dbfs) pga gain = 12thd = ?99 db snr = 120 db data rate = 500 sps g012 ?105 ?100 ?95 ?90 ?85 ?80 ?75 ?70 ?65 ?60 10 100 1000 frequency (hz) total harmonic distortion (db) gain = 1 gain = 2 gain = 4 gain = 6 gain = 8 gain = 12 gain = 24 data rate = 8 kspsa in = ?0.5 dbfs g009 ?10 ?8 ?6 ?4 ?2 0 2 4 6 8 10 12 ?1 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1 input (normalized to full-scale) integral nonlinearity (ppm) gain = 1gain = 2 gain = 4 gain = 6 gain = 8 gain = 12 gain = 24 g010 14 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated typical characteristics (continued) at t a = 25 c, avdd = 5 v, avss = 0 v, dvdd = 3.3 v, internal vrefp = 4.5 v, vrefn = avss, external clock = 2.048 mhz, data rate = 250 sps, and gain = 12 (unless otherwise noted) figure 15. test signal amplitude accuracy figure 16. lead-off comparator threshold accuracy figure 17. lead-off current source accuracy distribution ?3.5 ?3 ?2.5 ?2 ?1.5 ?1 ?0.5 0 0.5 1 1.5 2 2.5 ?3.5 ?3 ?2.5 ?2 ?1.5 ?1 ?0.5 0 0.5 1 1.5 2 2.5 0 50 100 150 200 250 300 350 error in current magnitude (na) number of bins current setting = 24 na g017 8070 60 50 40 30 20 10 0 - 20 threshold error (mv) number of bins - 15 0 1020 30 35 25 15 5 - 10 data from 31 devices, two lots g016 7060 50 40 30 20 10 0 - 0.53 error (%) number of bins - 0.41 - 0.18 0.06 0.3 0.54 0.66 0.42 0.18 - 0.06 - 0.29 data from 31 devices, two lots g015 15 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) at least 1000 consecutive readings were used to calculate the rms and peak-to-peak noise values in this table. 8 parametric measurement information 8.1 noise measurements note unless otherwise noted, ads1299-x refers to all specifications and functional descriptions of the ads1299-4, ads1299-6, and ads1299. optimize the ads1299-x noise performance by adjusting the data rate and pga setting. reduce the data rate to increase the averaging, and the noise drops correspondingly. increase the pga value to reduce the input- referred noise. this lowered noise level is particularly useful when measuring low-level biopotential signals. table 1 to table 4 summarize the ads1299-x noise performance with a 5-v analog power supply. the data are representative of typical noise performance at t a = +25 c. the data shown are the result of averaging the readings from multiple devices and are measured with the inputs shorted together. a minimum of 1000 consecutive readings are used to calculate the rms and peak-to-peak noise for each reading. for the lower data rates, the ratio is approximately 6.6. table 1 shows measurements taken with an internal reference. the data are also representative of the ads1299-x noise performance when using a low-noise external reference such as the ref5045 . table 1 , table 2 , table 3 , and table 4 list the input-referred noise in units of v rms and v pp for the conditions shown. the corresponding data in units of effective number of bits (enob) where enob for the rms noise is defined as in equation 1 : (1) noise-free bits for the peak-to-peak noise are calculated with the same method. the dynamic range data in table 1 , table 2 , table 3 , and table 4 are calculated using equation 2 : (2) table 1. input-referred noise ( v rms , v pp ) in normal mode 5-v analog supply and 4.5-v reference (1) dr bits of config1 register output data rate (sps) ? 3-db bandwidth (hz) pga gain = 1 pga gain = 2 v rms v pp dynamic range (db) noise- free bits enob v rms v pp dynamic range (db) noise- free bits enob 000 16000 4193 21.70 151.89 103.3 15.85 17.16 10.85 75.94 103.3 15.85 17.16 001 8000 2096 6.93 48.53 113.2 17.50 18.81 3.65 25.52 112.8 17.43 18.74 010 4000 1048 4.33 30.34 117.3 18.18 19.49 2.28 15.95 116.9 18.11 19.41 011 2000 524 3.06 21.45 120.3 18.68 19.99 1.61 11.29 119.9 18.60 19.91 100 1000 262 2.17 15.17 123.3 19.18 20.49 1.14 7.98 122.9 19.10 20.41 101 500 131 1.53 10.73 126.3 19.68 20.99 0.81 5.65 125.9 19.60 20.91 110 250 65 1.08 7.59 129.3 20.18 21.48 0.57 3.99 128.9 20.10 21.41 111 n/a n/a ? ? ? ? ? ? ? ? ? ? rms vref dynamic range = 20 log 2 gain v u ? ? u u ? 1 2 rms vref enob = log 2 gain v ? ? u u ? 1 16 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) at least 1000 consecutive readings were used to calculate the rms and peak-to-peak noise values in this table. table 2. input-referred noise ( v rms , v pp ) in normal mode 5-v analog supply and 4.5-v reference (1) dr bits of config1 register output data rate (sps) ? 3-db bandwidth (hz) pga gain = 4 pga gain = 6 v rms v pp dynamic range (db) noise- free bits enob v rms v pp dynamic range (db) noise- free bits enob 000 16000 4193 5.60 39.23 103.0 15.81 17.12 3.87 27.10 102.7 15.76 17.06 001 8000 2096 1.98 13.87 112.1 17.31 18.62 1.31 9.19 112.1 17.32 18.62 010 4000 1048 1.24 8.66 116.1 17.99 19.29 0.93 6.50 115.1 17.82 19.12 011 2000 524 0.88 6.13 119.2 18.49 19.79 0.66 4.60 118.1 18.32 19.62 100 1000 262 0.62 4.34 122.2 18.99 20.29 0.46 3.25 121.1 18.81 20.12 101 500 131 0.44 3.07 125.2 19.49 20.79 0.33 2.30 124.1 19.31 20.62 110 250 65 0.31 2.16 128.2 19.99 21.30 0.23 1.62 127.2 19.82 21.13 111 n/a n/a ? ? ? ? ? ? ? ? ? ? (1) at least 1000 consecutive readings were used to calculate the rms and peak-to-peak noise values in this table. table 3. input-referred noise ( v rms , v pp ) in normal mode 5-v analog supply and 4.5-v reference (1) dr bits of config1 register output data rate (sps) ? 3-db bandwidth (hz) pga gain = 8 pga gain = 12 v rms v pp dynamic range (db) noise- free bits enob v rms v pp dynamic range (db) noise- free bits enob 000 16000 4193 3.05 21.32 102.3 15.69 16.99 2.27 15.89 101.3 15.53 16.83 001 8000 2096 1.11 7.80 111.0 17.14 18.45 0.92 6.41 109.2 16.84 18.14 010 4000 1048 0.79 5.52 114.0 17.64 18.95 0.65 4.53 112.2 17.34 18.64 011 2000 524 0.56 3.90 117.1 18.14 19.44 0.46 3.20 115.2 17.84 19.14 100 1000 262 0.39 2.76 120.1 18.64 19.94 0.32 2.26 118.3 18.34 19.65 101 500 131 0.28 1.95 123.1 19.14 20.44 0.23 1.61 121.2 18.83 20.14 110 250 65 0.20 1.38 126.1 19.64 20.95 0.16 1.13 124.3 19.34 20.65 111 n/a n/a ? ? ? ? ? ? ? ? ? ? (1) at least 1000 consecutive readings were used to calculate the rms and peak-to-peak noise values in this table. table 4. input-referred noise ( v rms , v pp ) in normal mode 5-v analog supply and 4.5-v reference (1) dr bits of config1 register output data rate (sps) ? 3-db bandwidth (hz) pga gain = 24 v rms v pp dynamic range (db) noise-free bits enob 000 16000 4193 1.66 11.64 98.0 14.98 16.28 001 8000 2096 0.80 5.57 104.4 16.04 17.35 010 4000 1048 0.56 3.94 107.4 16.54 17.84 011 2000 524 0.40 2.79 110.4 17.04 18.35 100 1000 262 0.28 1.97 113.5 17.54 18.85 101 500 131 0.20 1.39 116.5 18.04 19.35 110 250 65 0.14 0.98 119.5 18.54 19.85 111 n/a n/a ? ? ? ? ? 17 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9 detailed description 9.1 overview the ads1299-x is a low-noise, low-power, multichannel, simultaneously-sampling, 24-bit, delta-sigma ( ) analog-to-digital converter (adc) with an integrated programmable gain amplifier (pga). these devices integrate various eeg-specific functions that makes the family well-suited for scalable electrocardiogram (ecg), electroencephalography (eeg) applications. these devices can also be used in high-performance, multichannel, data acquisition systems by powering down the ecg or eeg-specific circuitry. the devices have a highly-programmable multiplexer that allows for temperature, supply, input short, and bias measurements. additionally, the multiplexer allows any input electrodes to be programmed as the patient reference drive. the pga gain can be chosen from one of seven settings (1, 2, 4, 6, 8, 12, and 24). the adcs in the device offer data rates from 250 sps to 16 ksps. communication to the device is accomplished using an spi-compatible interface. the device provides four general-purpose input/output (gpio) pins for general use. multiple devices can be synchronized using the start pin. the internal reference generates a low noise 4.5 v internal voltage when enabled and the internal oscillator generates a 2.048-mhz clock when enabled. the versatile patient bias drive block allows the average of any electrode combination to be chosen in order to generate the patient drive signal. lead-off detection can be accomplished by using a current source or sink. a one-time, in-band, lead-off option and a continuous, out-of- band, internal lead-off option are available. 18 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.2 functional block diagram drdy clk clksel start mux oscillator power-supply signal spi dvdd dgnd bias inv bias out bias ref lead-off excitation source gpio1gpio4 gpio3 cs sclk dindout gpio2 in8p in8n in7p in7n in6p in6n in5p in5n in4p in4n in3p in3n in2p in2n in1p in1n low-noise pga1 ds adc1 temperature sensor input bias amplifier reference vrefp vrefn control pwdn reset ds adc2 ds adc3 ds adc4 ds adc5 ds adc6 ds adc7 ds adc8 avdd avdd1 avss avss1 test signal biasin srb2 srb1 low-noise pga8 low-noise pga7 low-noise pga6 low-noise pga5 low-noise pga4 low-noise pga3 low-noise pga2 ads1299-6 and ads1299 only ads1299 only 19 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3 feature description this section contains details of the ads1299-x internal functional elements. the analog blocks are discussed first, followed by the digital interface. blocks implementing eeg-specific functions are covered at the end of this section. throughout this document, f clk denotes the clk pin signal frequency, t clk denotes the clk pin signal period, f dr denotes the output data rate, t dr denotes the output data time period, and f mod denotes the frequency at which the modulator samples the input. 9.3.1 analog functionality 9.3.1.1 input multiplexer the ads1299-x input multiplexers are very flexible and provide many configurable signal-switching options. figure 18 shows the multiplexer on a single channel of the device. note that the device has either four (ads1299-4), six (ads1299-6) or eight (ads1299) such blocks, one for each channel. srb1, srb2, and biasin are common to all blocks. inxp and inxn are separate for each of the four, six, or eight blocks. this flexibility allows for significant device and sub-system diagnostics, calibration, and configuration. switch setting selections for each channel by writing the appropriate values to the chnset[3:0] register (see the chnset: individual channel settings section for details) using the bias_meas bit in the config3 register and the srb1 bit in the misc1 register (see the config3: configuration register 3 subsection of the register maps section for details). see the input multiplexer section for further information regarding the eeg-specific features of the multiplexer. (1) main is equal to either mux[2:0] = 000, mux[2:0] = 110, or mux[2:0] = 111. figure 18. input multiplexer block for one channel mux[2:0] = 101 tempp mux[2:0] = 100 mvddp mux[2:0] = 011 from loffp main (1) mux[2:0] = 110 mux[2:0] = 001 to pgap to pgan mux[2:0] = 001 mux[2:0] = 111 inxp inxn main (1) and srb1 from loffn (avdd+avss) 2 mvddn tempn ti device mux int_test (vrefp + vrefn) 2 testp int_test testm srb2 bias_in to next channels chxset[3] = 1 srb1 to next channels main (1) and srb1 mux[2:0] = 010 and bias_meas mux[2:0] = 010 and bias_meas biasref_int=1 biasref_int=0 mux[2:0] = 100 mux[2:0] = 011 mux[2:0] = 101 biasref copyright ? 2016, texas instruments incorporated 20 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated feature description (continued) 9.3.1.1.1 device noise measurements setting chnset[2:0] = 001 sets the common-mode voltage of [(v vrefp + v vrefn ) / 2] to both channel inputs. this setting can be used to test inherent device noise in the user system. 9.3.1.1.2 test signals (testp and testn) setting chnset[2:0] = 101 provides internally-generated test signals for use in sub-system verification at power- up. this functionality allows the device internal signal chain to be tested out. test signals are controlled through register settings (see the config2: configuration register 2 subsection in the register maps section for details). test_amp controls the signal amplitude and test_freq controls switching at the required frequency. 9.3.1.1.3 temperature sensor (tempp, tempn) the ads1299-x contains an on-chip temperature sensor. this sensor uses two internal diodes with one diode having a current density 16x that of the other, as shown in figure 19 . the difference in diode current densities yields a voltage difference proportional to absolute temperature. as a result of the low thermal resistance of the package to the printed circuit board (pcb), the internal device temperature tracks pcb temperature closely. note that self-heating of the ads1299-x causes a higher reading than the temperature of the surrounding pcb. the scale factor of equation 3 converts the temperature reading to degrees celsius. before using this equation, the temperature reading code must first be scaled to microvolts. (3) figure 19. temperature sensor measurement in the input 9.3.1.1.4 supply measurements (mvddp, mvddn) setting chnset[2:0] = 011 sets the channel inputs to different supply voltages of the device. for channels 1, 2, 5, 6, 7, and 8, (mvddp ? mvddn) is [0.5 (avdd + avss)]. for channels 3 and 4, (mvddp ? mvddn) is dvdd / 4. to avoid saturating the pga when measuring power supplies, set the gain to 1. 9.3.1.1.5 lead-off excitation signals (loffp, loffn) the lead-off excitation signals are fed into the multiplexer before the switches. the comparators that detect the lead-off condition are also connected to the multiplexer block before the switches. for a detailed description of the lead-off block, see the lead-off detection section. 2x 1x 1x 8x avdd avss temperature sensor monitor to mux tempp to mux tempn temperature ( c) = temperature reading ( v) 145,300 v m - m 490 v/ c m + 25 c 21 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated feature description (continued) 9.3.1.1.6 auxiliary single-ended input the biasin pin is primarily used for routing the bias signal to any electrodes in case the bias electrode falls off. however, the biasin pin can be used as a multiple single-ended input channel. the signal at the biasin pin can be measured with respect to the voltage at the biasref pin using any of the eight channels. this measurement is done by setting the channel multiplexer setting to '010' and the bias_meas bit of the config3 register to '1'. 9.3.1.2 analog input the ads1299-x analog input is fully differential. assuming pga = 1, the input (inxp ? inxn) can span between ? v ref to +v ref . see table 9 for an explanation of the correlation between the analog input and digital codes. there are two general methods of driving the ads1299-x analog input: single-ended or differential (as shown in figure 20 and figure 21 , respectively). note that inxp and inxn are 180 out-of-phase in the differential input method. when the input is single-ended, the inxn input is held at the common-mode voltage (cm), preferably at mid-supply. the inxp input swings around the same common voltage and the peak-to-peak amplitude is (cm + v ref ) and (cm ? v ref ). when the input is differential, the common-mode is given by [(inxp + inxn) / 2]. both inxp and inxn inputs swing from (cm + 1/2 v ref ) to (cm ? 1/2 v ref ). drive the inputs of the ads1299-x in a differential configuration for optimal performance. figure 20. methods of driving the ads1299-x: single-ended or differential figure 21. using the ads1299-x in single-ended and differential input modes + v ref - v ref single-ended inputs t inp cm voltage differential inputs t inp inn cm voltage +v ref - v ref common-mode voltage (differential mode) = (inp) + (inn) 2 , common-mode voltage (single-ended mode) = inn inn = cm voltage cm + v ref cm - v ref cm - 1/2 v ref cm + 1/2 v ref input range (differential mode) = (ainp ainn) = 2 v ref a) single-ended input b) differential input ti device common voltage - v ref to + v ref ti device v peak-to-peak ref v peak-to-peak ref common voltage copyright ? 2016, texas instruments incorporated 22 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.1.3 pga settings and input range the low-noise pga is a differential input and output amplifier, as shown in figure 22 . the pga has seven gain settings (1, 2, 4, 6, 8, 12, and 24) that can be set by writing to the chnset register (see the chnset: individual channel settings subsection of the register maps section for details). the ads1299-x has cmos inputs and therefore has negligible current noise. table 5 shows the typical bandwidth values for various gain settings. note that table 5 shows small-signal bandwidth. for large signals, performance is limited by pga slew rate. figure 22. pga implementation table 5. pga gain versus bandwidth gain nominal bandwidth at room temperature (khz) 1 662 2 332 4 165 6 110 8 83 12 55 24 27 the pga resistor string that implements the gain has 39.6 k ? of resistance for a gain of 12. this resistance provides a current path across the pga outputs in the presence of a differential input signal. this current is in addition to the quiescent current specified for the device in the presence of a differential signal at the input. 9.3.1.3.1 input common-mode range to stay within the linear operating range of the pga, the input signals must meet certain requirements that are discussed in this section. the outputs of the amplifiers in figure 22 cannot swing closer to the supplies (avss and avdd) than 200 mv. if the outputs of the amplifiers are driven to within 200 mv of the supply rails, then the amplifiers saturate and consequently become nonlinear. to prevent this nonlinear operating condition, the output voltages must not exceed the common-mode range of the front-end. the usable input common-mode range of the front-end depends on various parameters, including the maximum differential input signal, supply voltage, pga gain, and the 200 mv for the amplifier headroom. this range is described in equation 4 : where: v max_diff = maximum differential signal at the pga input cm = common-mode range (4) max _ diff max _ diff gain v gain v avdd 0.2 v cm avss 0.2 v 2 2 ? ? ? ? - - > > + + ? ? ? ? ? ? low-noise pgap r18.15 k w 2 r3.3 k (for gain = 12) w 1 r18.15 k w 2 from muxp low-noise pgan from muxn to adc 23 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated for example: if avdd = 5 v, gain = 12, and v max_diff = 350 mv then 2.3 v < cm < 2.7 v 9.3.1.3.2 input differential dynamic range the differential input voltage range (v inxp ? v inxn ) depends on the analog supply and reference used in the system . this range is shown in equation 5 . (5) 9.3.1.3.3 adc modulator each ads1299-x channel has a 24-bit, adc. this converter uses a second-order modulator optimized for low-noise applications. the modulator samples the input signal at the rate of (f mod = f clk / 2). as in the case of any modulator, the device noise is shaped until f mod / 2, as shown in figure 23 . the on-chip digital decimation filters explained in the next section can be used to filter out the noise at higher frequencies. these on-chip decimation filters also provide antialias filtering. this converter feature drastically reduces the complexity of the analog antialiasing filters typically required with nyquist adcs. figure 23. modulator noise spectrum up to 0.5 f mod 9.3.1.3.4 reference figure 24 shows a simplified block diagram of the ads1299-x internal reference. the 4.5-v reference voltage is generated with respect to avss. when using the internal voltage reference, connect v refn to avss. (1) for v ref = 4.5 v: r1 = 9.8 k , r2 = 13.4 k , and r3 = 36.85 k . figure 24. internal reference 100 f m to adc reference inputs vcap1 10 f m vrefpvrefn bandgap 4.5 v avss r1 (1) r3 (1) r2 (1) ?160 ?150 ?140 ?130 ?120 ?110 ?100 ?90 ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 0 0.001 0.01 0.1 1 normalized frequency (f in /f mod ) power spectral density (db) g001 ref ref v 2v full-scale range gain gain = = 24 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated the external band-limiting capacitors determine the amount of reference noise contribution. for high-end eeg systems, the capacitor values should be chosen such that the bandwidth is limited to less than 10 hz so that the reference noise does not dominate system noise. alternatively, the internal reference buffer can be powered down and an external reference can be applied to vrefp. figure 25 shows a typical external reference drive circuitry. power-down is controlled by the pd_refbuf bit in the config3 register. this power-down is also used to share internal references when two devices are cascaded. by default, the device wakes up in external reference mode. figure 25. external reference driver 9.3.2 digital functionality 9.3.2.1 digital decimation filter the digital filter receives the modulator output and decimates the data stream. by adjusting the amount of filtering, tradeoffs can be made between resolution and data rate: filter more for higher resolution, filter less for higher data rates. higher data rates are typically used in eeg applications for ac lead-off detection. the digital filter on each channel consists of a third-order sinc filter. the sinc filter decimation ratio can be adjusted by the dr bits in the config1 register (see the register maps section for details). this setting is a global setting that affects all channels and, therefore, all channels operate at the same data rate in a device. 9.3.2.1.1 sinc filter stage (sinx / x) the sinc filter is a variable decimation rate, third-order, low-pass filter. data are supplied to this section of the filter from the modulator at the rate of f mod . the sinc filter attenuates the modulator high-frequency noise, then decimates the data stream into parallel data. the decimation rate affects the overall converter data rate. equation 6 shows the scaled z-domain transfer function of the sinc filter. (6) the frequency domain transfer function of the sinc filter is shown in equation 7 . where: n = decimation ratio (7) ? h(f) = ? 3 sin n f p f mod n sin p f f mod ? h(z) = ? 3 1 z - - n 1 z - - 1 100 100 k 10 opa350 22 nf 0.1 f +5 v 0.1 f 10 f 100 f 10 f out vin 5 v trim 1 f ref5025 to vrefp pin 25 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated the sinc filter has notches (or zeroes) that occur at the output data rate and multiples thereof. at these frequencies, the filter has infinite attenuation. figure 26 shows the sinc filter frequency response and figure 27 shows the sinc filter roll-off. with a step change at input, the filter takes 3 t dr to settle. after a rising edge of the start signal, the filter takes t settle time to give the first data output. the settling time of the filters at various data rates are discussed in the start subsection of the spi interface section. figure 28 and figure 29 show the filter transfer function until f mod / 2 and f mod / 16, respectively, at different data rates. figure 30 illustrates the transfer function extended until 4 f mod . the ads1299-x pass band repeats itself at every f mod . the input r-c antialiasing filters in the system should be chosen such that any interference in frequencies around multiples of f mod are attenuated sufficiently. figure 26. sinc filter frequency response figure 27. sinc filter roll-off figure 28. transfer function of on-chip decimation filters until f mod / 2 figure 29. transfer function of on-chip decimation filters until f mod / 16 0 0.5 1 1.5 2 2.5 3 - - - - - - normalized frequency (f / f ) in dr gain (db) 0.05 0.1 0 0.15 0.35 0.2 0.25 0.3 ?160 ?140 ?120 ?100 ?80 ?60 ?40 ?20 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 normalized frequency (f in /f mod ) gain (db) dr[2:0] = 000dr[2:0] = 001 dr[2:0] = 010 dr[2:0] = 011 dr[2:0] = 100dr[2:0] = 101 dr[2:0] = 110 g027 ?140 ?120 ?100 ?80 ?60 ?40 ?20 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 normalized frequency (f in /f mod ) gain (db) dr[2:0] = 000dr[2:0] = 001 dr[2:0] = 010 dr[2:0] = 011 dr[2:0] = 100dr[2:0] = 101 dr[2:0] = 110 g028 0 - 20 - 40 - 60 - 80 - 100 - 120 - 140 normalized frequency (f / f ) in dr gain (db) 1 2 0 3 4 5 0.5 4.5 3.5 2.5 1.5 26 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated figure 30. transfer function of on-chip decimation filters until 4 f mod for dr[2:0] = 000 and dr[2:0] = 110 9.3.2.2 clock the ads1299-x provides two methods for device clocking: internal and external. internal clocking is ideally suited for low-power, battery-powered systems. the internal oscillator is trimmed for accuracy at room temperature. accuracy varies over the specified temperature range; see the electrical characteristics . clock selection is controlled by the clksel pin and the clk_en register bit. the clksel pin selects either the internal or external clock. the clk_en bit in the config1 register enables and disables the oscillator clock to be output in the clk pin. a truth table for these two pins is shown in table 6 . the clk_en bit is useful when multiple devices are used in a daisy-chain configuration. during power-down, the external clock is recommended be shut down to save power. table 6. clksel pin and clk_en bit clksel pin config1.clk_en bit clock source clk pin status 0 x external clock input: external clock 1 0 internal clock oscillator 3-state 1 1 internal clock oscillator output: internal clock oscillator ?140 ?120 ?100 ?80 ?60 ?40 ?20 0 0 0.5 1 1.5 2 2.5 3 3.5 4 normalized frequency (f in /f mod ) gain (db) g029 27 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.3 gpio the ads1299-x has a total of four general-purpose digital i/o (gpio) pins available in normal mode of operation. the digital i/o pins are individually configurable as either inputs or outputs through the gpioc bits register. the gpiod bits in the gpio register control the pin level. when reading the gpiod bits, the data returned are the logic level of the pins, whether they are programmed as inputs or outputs. when the gpio pin is configured as an input, a write to the corresponding gpiod bit has no effect. when configured as an output, a write to the gpiod bit sets the output value. if configured as inputs, these pins must be driven (do not float). the gpio pins are set as inputs after power-on or after a reset. figure 31 shows the gpio port structure. the pins should be shorted to dgnd if not used. figure 31. gpio port pin gpio pin gpio data (read) gpio data (write) gpio control 28 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.4 ecg and eeg specific features 9.3.2.4.1 input multiplexer (rerouting the bias drive signal) the input multiplexer has eeg-specific functions for the bias drive signal. the bias signal is available at the biasout pin when the appropriate channels are selected for bias derivation, feedback elements are installed external to the chip, and the loop is closed. this signal can either be fed after filtering or fed directly into the biasin pin, as shown in figure 32 . this biasin signal can be multiplexed into any input electrode by setting the mux bits of the appropriate channel set registers to '110' for p-side or '111' for n-side. figure 32 shows the bias signal generated from channels 1, 2, and 3 and routed to the n-side of channel 8. this feature can be used to dynamically change the electrode that is used as the reference signal to drive the patient body. (1) typical values for example only. figure 32. example of biasout signal configured to be routed to in8n mux1[2:0] = 000 bias_sensp[0] = 1 bias_sensn[0] = 1 mux2[2:0] = 000 mux3[2:0] = 000 mux8[2:0] = 111 low-noise pga1 bias_sensp[1] = 1 bias_sensn[1] = 1 low-noise pga2 bias_sensp[2] = 1 bias_sensn[2] = 1 low-noise pga3 bias_amp bias_sensp[7] = 0 bias_sensn[7] = 0 low-noise pga8 biasout biasinv biasref biasin filter or feedthrough device ? ? mux in1p ? in1n in2pin3p in8p in2nin3n in8n 1 m w (1) 1.5 nf (1) (avdd + avss) 2 biasref_int = 1 biasref_int = 0 29 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.4.2 input multiplexer (measuring the bias drive signal) also, the biasout signal can be routed to a channel (that is not used for the calculation of bias) for measurement. figure 33 shows the register settings to route the biasin signal to channel 8. the measurement is done with respect to the voltage on the biasref pin. if biasref is chosen to be internal, then biasref is at [(avdd + avss) / 2]. this feature is useful for debugging purposes during product development. (1) typical values for example only. figure 33. biasout signal configured to be read back by channel 8 mux1[2:0] = 000 bias_sensp[0] = 1 bias_sensn[0] = 1 mux2[2:0] = 000 mux3[2:0] = 000 bias_meas = 1 low-noise pga1 bias_sensp[1] = 1 bias_sensn[1] = 1 low-noise pga2 bias_sensp[2] = 1 bias_sensn[2] = 1 low-noise pga3 bias_amp bias_sensp[7] = 0 bias_sensn[7] = 0 low-noise pga8 biasout biasinv biasref biasin filter or feedthrough ti device ? ? in1p in1n mux ? in2nin3n in8n in2pin3p in8p mux8[2:0] = 010 1 m w (1) 1.5 nf (1) biasref_int = 1 biasref_int = 0 (avdd + avss) 2 copyright ? 2016, texas instruments incorporated 30 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.4.3 lead-off detection patient electrode impedances are known to decay over time. these electrode connections must be continuously monitored to verify that a suitable connection is present. the ads1299-x lead-off detection functional block provides significant flexibility to the user to choose from various lead-off detection strategies. though called lead- off detection, this is in fact an electrode-off detection. the basic principle is to inject an excitation current and measure the voltage to determine if the electrode is off. as shown in the lead-off detection functional block diagram in figure 34 , this circuit provides two different methods of determining the state of the patient electrode. the methods differ in the frequency content of the excitation signal. lead-off can be selectively done on a per channel basis using the loff_sensp and loff_sensn registers. also, the internal excitation circuitry can be disabled and just the sensing circuitry can be enabled. figure 34. lead-off detection 51 k w 51 k w z 1 47 nf z 2 47 nf skin, electrode contact model patient protection resistor avdd loff_sensp avss loff_sensn to adc v inp v inn patient flead_off[0:1] 6 na and 24 na 6 a and 24 a m m 51 k w z 3 47 nf bias out 31 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.4.3.1 dc lead-off in this method, the lead-off excitation is with a dc signal. the dc excitation signal can be chosen from either an external pull-up or pull-down resistor or an internal current source or sink, as shown in figure 35 . one side of the channel is pulled to supply and the other side is pulled to ground. the pull-up and pull-down current can be swapped (as shown in figure 35 b and figure 35 c) by setting the bits in the loff_flip register. in case of a current source or sink, the magnitude of the current can be set by using the ilead_off[1:0] bits in the loff register. the current source or sink gives larger input impedance compared to the 10-m ? pull-up or pull-down resistor. figure 35. dc lead-off excitation options sensing of the response can be done either by searching the digital output code from the device or by monitoring the input voltages with an on-chip comparator. if either electrode is off, the pull-up and pull-down resistors saturate the channel. searching the output code determines if either the p-side or the n-side is off. to pinpoint which one is off, the comparators must be used. the input voltage is also monitored using a comparator and a 3- bit dac whose levels are set by the comp_th[2:0] bits in the loff register. the output of the comparators are stored in the loff_statp and loff_statn registers. these registers are available as a part of the output data stream. (see the data output (dout) subsection of the spi interface section.) if dc lead-off is not used, the lead-off comparators can be powered down by setting the pd_loff_comp bit in the config4 register. an example procedure to turn on dc lead-off is given in the lead-off section. 9.3.2.4.3.2 ac lead-off (one time or periodic) in this method, an in-band ac signal is used for excitation. the ac signal is generated by alternatively providing a current source and sink at the input with a fixed frequency. the frequency can be chosen by the flead_off[1:0] bits in the loff register. the excitation frequency is chosen to be one of the two in-band frequency selections (7.8 hz or 31.2 hz). this in-band excitation signal is passed through the channel and measured at the output. sensing of the ac signal is done by passing the signal through the channel to be digitized and then measured at the output. the ac excitation signals are introduced at a frequency that is in the band of interest. the signal can be filtered out separately and processed. by measuring the magnitude of the output at the excitation signal frequency, the electrode impedance can be calculated. for continuous lead-off, an out-of-band ac current source or sink must be externally applied to the inputs. this signal can then be digitally processed to determine the electrode impedance. a) external pull-up or pull-down resistors b) input current source (loff_flip = 0) low-noise pgan 10 m w 10 m w avdd inp inn device avdd inp inn device low-noise pgan c) input current source (loff_flip = 1) avdd inp inn device low-noise pgan avss 32 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.4.4 bias lead-off bias lead-off detection during normal operation during normal operation, the ads1299-x bias lead-off at power-up function cannot be used because the bias amplifier must be powered off. bias lead off detection at power-up this feature is included in the ads1299-x for use in determining whether the bias electrode is suitably connected. at power-up, the ads1299-x uses a current source and comparator to determine the bias electrode connection status, as shown in figure 36 . the reference level of the comparator is set to determine the acceptable bias impedance threshold. figure 36. bias lead-off detection at power-up when the bias amplifier is powered on, the current source has no function. only the comparator can be used to sense the voltage at the output of the bias amplifier. the comparator thresholds are set by the same loff[7:5] bits used to set the thresholds for other negative inputs. 51 k w 47 nf skin, electrode contact model patient protection resistor bias_stat patient avss bias_sens to adc input (through v connection to any of the channels). ref ilead_off[1:0] 33 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.3.2.4.5 bias drive (dc bias circuit) use the bias circuitry to counter the common-mode interference in a eeg system as a result of power lines and other sources, including fluorescent lights. the bias circuit senses the common-mode voltage of a selected set of electrodes and creates a negative feedback loop by driving the body with an inverted common-mode signal. the negative feedback loop restricts the common-mode movement to a narrow range, depending on the loop gain. stabilizing the entire loop is specific to the individual user system based on the various poles in the loop. the ads1299-x integrates the muxes to select the channel and an operational amplifier. all the amplifier terminals are available at the pins, allowing the user to choose the components for the feedback loop. the circuit in figure 37 shows the overall functional connectivity for the bias circuit. (1) typical values. figure 37. bias drive amplifier channel selection the reference voltage for the bias drive can be chosen to be internally generated [(avdd + avss) / 2] or provided externally with a resistive divider. the selection of an internal versus external reference voltage for the bias loop is defined by writing the appropriate value to the biasref_int bit in the config2 register. 220 k w 18.15 k w 18.15 k w bias1p 220 k w 3.3 k w bias1n 220 k w 18.15 k w 18.15 k w bias2p 3.3 k w 220 k w bias2n from mux1p from mux2p from mux2n from mux1n 220 k w 18.15 k w 18.15 k w bias3p 220 k w 3.3 k w bias3n 220 k w 18.15 k w 18.15 k w bias4p 3.3 k w 220 k w bias4n from mux3p from mux4p from mux4n from mux3n 220 k w 18.15 k w 18.15 k w bias5p 220 k w 3.3 k w bias5n 220 k w 18.15 k w 18.15 k w bias6p 3.3 k w 220 k w bias6n from mux5p from mux6p from mux6n (avdd + avss) / 2 biasout from mux5n 220 k w 18.15 k w 18.15 k w r (1) 1 m w ext c (1) 1.5 nf ext bias7p 220 k w 3.3 k w bias7n 220 k w 18.15 k w 18.15 k w bias8p 3.3 k w 220 k w bias8n biasref_int = 1 from mux7p from mux8p from mux8n from mux7n bias amp biasinv biasref biasref_int = 0 pga1ppga1n pga3p pga3n pga5p pga5n pga7p pga7n pga8n pga8p pga6n pga6p pga4n pga4p pga2n pga2p 34 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated if the bias function is not used, the amplifier can be powered down using the pd_bias bit (see the config3: configuration register 3 subsection of the register maps section for details). use the pd_bias bit to power- down all but one of the bias amplifiers when daisy-chaining multiple ads1299-x devices. the biasin pin functionality is explained in the input multiplexer section. an example procedure to use the bias amplifier is shown in the bias drive section. 9.3.2.4.5.1 bias configuration with multiple devices figure 38 shows multiple devices connected to the bias drive. figure 38. bias drive connection for multiple devices 9.4 device functional modes 9.4.1 start pull the start pin high for at least 2 t clk periods, or send the start command to begin conversions. when start is low and the start command has not been sent, the device does not issue a drdy signal (conversions are halted). when using the start command to control conversions, hold the start pin low. the ads1299-x features two modes to control conversions: continuous mode and single-shot mode. the mode is selected by single_shot (bit 3 of the config4 register). in multiple device configurations, the start pin is used to synchronize devices (see the multiple device configuration subsection of the spi interface section for more details). 9.4.1.1 settling time the settling time (t settle ) is the time required for the converter to output fully-settled data when the start signal is pulled high. when start is pulled high, drdy is also pulled high. the next drdy falling edge indicates that data are ready. figure 39 shows the timing diagram and table 7 shows the settling time for different data rates. the settling time depends on f clk and the decimation ratio (controlled by the dr[2:0] bits in the config1 register). when the initial settling time has passed, the drdy falling edge occurs at the set data rate, t dr . if data is not read back on dout and the output shift register needs to update, drdy goes high for 4 t clk before returning back low indicating new data is ready. table 9 shows the settling time as a function of t clk . note that when start is held high and there is a step change in the input signal, 3 t dr is required for the filter to settle to the new value. settled data are available on the fourth drdy pulse. figure 39. settling time start start pin din 4 / f clk drdy or t dr t settle biasinv bias out bias ref biasin va1-8 device 2 va1-8 biasinv bias out bias ref biasin va1-8 device n va1-8 power-down power-down biasinv bias out bias ref biasin va1-8 device 1 va1-8 to input mux to input mux to input mux 35 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated device functional modes (continued) table 7. settling time for different data rates dr[2:0] normal mode unit 000 521 t clk 001 1033 t clk 010 2057 t clk 011 4105 t clk 100 8201 t clk 101 16393 t clk 110 32777 t clk 9.4.2 reset ( reset) there are two methods to reset the ads1299-x: pull the reset pin low, or send the reset command. when using the reset pin, make sure to follow the minimum pulse duration timing specifications before taking the pin back high. the reset command takes effect on the eighth sclk falling edge of the command. after a reset, 18 t clk cycles are required to complete initialization of the configuration registers to default states and start the conversion cycle. note that an internal reset is automatically issued to the digital filter whenever the config1 register is set to a new value with a wreg command. 9.4.3 power-down ( pwdn) when pwdn is pulled low, all on-chip circuitry is powered down. to exit power-down mode, take the pwdn pin high. upon exiting from power-down mode, the internal oscillator and the reference require time to wake up. during power-down, the external clock is recommended to be shut down to save power. 9.4.4 data retrieval 9.4.4.1 data ready ( drdy) drdy is an output signal which transitions from high to low indicating new conversion data are ready. the cs signal has no effect on the data ready signal. drdy behavior is determined by whether the device is in rdatac mode or the rdata command is used to read data on demand. (see the rdatac: read data continuous and rdata: read data subsections of the spi command definitions section for further details). when reading data with the rdata command, the read operation can overlap the next drdy occurrence without data corruption. the start pin or the start command places the device either in normal data capture mode or pulse data capture mode. figure 40 shows the relationship between drdy, dout, and sclk during data retrieval (in case of an ads1299). dout is latched out at the sclk rising edge. drdy is pulled high at the sclk falling edge. note that drdy goes high on the first sclk falling edge, regardless of whether data are being retrieved from the device or a command is being sent through the din pin. figure 40. drdy with data retrieval ( cs = 0) drdy dout sclk bit 215 bit 214 bit 213 x 36 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated device functional modes (continued) 9.4.4.2 reading back data data retrieval can be accomplished in one of two methods: 1. rdatac: the read data continuous command sets the device in a mode that reads data continuously without sending commands. see the rdatac: read data continuous section for more details. 2. rdata: the read data command requires that a command is sent to the device to load the output shift register with the latest data. see the rdata: read data section for more details. conversion data are read by shifting data out on dout. the msb of the data on dout is clocked out on the first sclk rising edge. drdy returns high on the first sclk falling edge. din should remain low for the entire read operation. the number of bits in the data output depends on the number of channels and the number of bits per channel. for the 8-channel ads1299, the number of data outputs is [(24 status bits + 24 bits 8 channels) = 216 bits]. the format of the 24 status bits is: (1100 + loff_statp + loff_statn + bits[4:7] of the gpio register). the data format for each channel data are twos complement and msb first. when channels are powered down using the user register setting, the corresponding channel output is set to '0'. however, the channel output sequence remains the same. the ads1299-x also provides a multiple readback feature. data can be read out multiple times by simply giving more sclks in rdatac mode, in which case the msb data byte repeats after reading the last byte. the daisy_en bit in the config1 register must be set to '1' for multiple readbacks. 9.4.5 continuous conversion mode conversions begin when the start pin is taken high or when the start command is sent. as shown in figure 41 , the drdy output goes high when conversions are started and goes low when data are ready. conversions continue indefinitely until the start pin is taken low or the stop command is transmitted. when the start pin is pulled low or the stop command is issued, the conversion in progress is allowed to complete. figure 42 and table 8 show the required drdy timing to the start pin or the start and stop commands when controlling conversions in this mode. the t sdsu timing indicates when to take the start pin low or when to send the stop command before the drdy falling edge to halt further conversions. the t dshd timing indicates when to take the start pin low or send the stop command after a drdy falling edge to complete the current conversion and halt further conversions. to keep the converter running continuously, the start pin can be permanently tied high. when switching from single-shot mode to continuous conversion mode, bring the start signal low and back high or send a stop command followed by a start command. this conversion mode is ideal for applications that require a fixed continuous stream of conversions results. (1) start and stop commands take effect on the seventh sclk falling edge. figure 41. continuous conversion mode start (1) start pin din t dr t settle drdy stop (1) or or 37 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated device functional modes (continued) (1) start and stop commands take effect on the seventh sclk falling edge at the end of the command. (1) start and stop commands take effect on the seventh sclk falling edge at the end of the command. figure 42. start to drdy timing table 8. timing characteristics for figure 42 (1) symbol description min unit t sdsu start pin low or stop command to drdy setup time to halt further conversions 16 t clk t dshd start pin low or stop command to complete current conversion 16 t clk 9.4.6 single-shot mode single-shot mode is enabled by setting the single_shot bit in the config4 register to '1'. in single-shot mode, the ads1299-x performs a single conversion when the start pin is taken high or when the start command is sent. as shown in figure 43 , when a conversion is complete, drdy goes low and further conversions are stopped. regardless of whether the conversion data are read or not, drdy remains low. to begin a new conversion, take the start pin low and then back high, or send the start command again. when switching from continuous conversion mode to single-shot mode, bring the start signal low and back high or send a stop command followed by a start command. figure 43. drdy with no data retrieval in single-shot mode this conversion mode is ideal for applications that require non-standard or non-continuous data rates. issuing a start command or toggling the start pin high resets the digital filter, effectively dropping the data rate by a factor of four. this mode leaves the system more susceptible to aliasing effects, requiring more complex analog or digital filtering. loading on the host processor increases because the processor must toggle the start pin or send a start command to initiate a new conversion cycle. 9.5 programming 9.5.1 data format the device provides 24 bits of data in binary twos complement format. the size of one code (lsb) is calculated using equation 8 . 1 lsb = (2 v ref / gain) / 2 24 = +fs / 2 23 (8) a positive full-scale input produces an output code of 7fffffh and the negative full-scale input produces an output code of 800000h. the output clips at these codes for signals exceeding full-scale. table 9 summarizes the ideal output codes for different input signals. all 24 bits toggle when the analog input is at positive or negative full-scale. start drdy 4 / f clk 4 / f clk data updating t settle t sdsu t dshd stop command drdy and dout start pin or stop (1) stop (1) 38 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) only valid for 24-bit resolution data rates. (2) excludes effects of noise, linearity, offset, and gain error. table 9. ideal output code versus input signal (1) input signal, v in (inxp - inxn) ideal output code (2) v ref 7fffffh +v ref / (2 23 ? 1) 000001h 0 000000h ? v ref / (2 23 ? 1) ffffffh ? v ref (2 23 / 2 23 ? 1) 800000h 9.5.2 spi interface the spi-compatible serial interface consists of four signals: cs, sclk, din, and dout. the interface reads conversion data, reads and writes registers, and controls ads1299-x operation. the data-ready output, drdy (see the data ready ( drdy) section), is used as a status signal to indicate when data are ready. drdy goes low when new data are available. 9.5.2.1 chip select ( cs) the cs pin activates spi communication. cs must be low before data transactions and must stay low for the entire spi communication period. when cs is high, the dout pin enters a high-impedance state. therefore, reading and writing to the serial interface are ignored and the serial interface is reset. drdy pin operation is independent of cs. drdy still indicates that a new conversion has completed and is forced high as a response to sclk, even if cs is high. taking cs high deactivates only the spi communication with the device and the serial interface is reset. data conversion continues and the drdy signal can be monitored to check if a new conversion result is ready. a master device monitoring the drdy signal can select the appropriate slave device by pulling the cs pin low. after the serial communication is finished, always wait four or more t clk cycles before taking cs high. 9.5.2.2 serial clock (sclk) sclk provides the clock for serial communication. sclk is a schmitt-trigger input, but ti recommends keeping sclk as free from noise as possible to prevent glitches from inadvertently shifting the data. data are shifted into din on the falling edge of sclk and shifted out of dout on the rising edge of sclk. the absolute maximum sclk limit is specified in figure 1 . when shifting in commands with sclk, make sure that the entire set of sclks is issued to the device. failure to do so can result in the device serial interface being placed into an unknown state requiring cs to be taken high to recover. for a single device, the minimum speed required for sclk depends on the number of channels, number of bits of resolution, and output data rate. (for multiple cascaded devices, see the cascaded mode subsection of the multiple device configuration section.) for example, if the ads1299 is used in a 500-sps mode (8 channels, 24-bit resolution), the minimum sclk speed is 110 khz. data retrieval can be accomplished either by placing the device in rdatac mode or by issuing an rdata command for data on demand. the sclk rate limitation in equation 9 applies to rdatac. for the rdata command, the limitation applies if data must be read in between two consecutive drdy signals. equation 9 assumes that there are no other commands issued in between data captures. (9) 9.5.2.3 data input (din) din is used along with sclk to send data to the device. data on din are shifted into the device on the falling edge of sclk. t < sclk t 4 t dr clk - n n + 24 bits channels 39 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) when in rdatac mode, the rreg command is ignored. (2) n nnnn = number of registers to be read or written ? 1. for example, to read or write three registers, set n nnnn = 0 (0010). r rrrr = starting register address for read or write commands. the communication of this device is full-duplex in nature. the device monitors commands shifted in even when data are being shifted out. data that are present in the output shift register are shifted out when sending in a command. therefore, make sure that whatever is being sent on the din pin is valid when shifting out data. when no command is to be sent to the device when reading out data, send the nop command on din. make sure that the t sdecode timing is met in the sending multi-byte commands section when sending multiple byte commands on din. 9.5.2.4 data output (dout) dout is used with sclk to read conversion and register data from the device. data are clocked out on the rising edge of sclk, msb first. dout goes to a high-impedance state when cs is high. figure 44 shows the ads1299 data output protocol. figure 44. spi bus data output 9.5.3 spi command definitions the ads1299-x provides flexible configuration control. the commands, summarized in table 10 , control and configure device operation. the commands are stand-alone, except for the register read and write operations that require a second command byte plus data. cs can be taken high or held low between commands but must stay low for the entire command operation (especially for multi-byte commands). system commands and the rdata command are decoded by the device on the seventh sclk falling edge. the register read and write commands are decoded on the eighth sclk falling edge. be sure to follow spi timing requirements when pulling cs high after issuing a command. table 10. command definitions command description first byte second byte system commands wakeup wake-up from standby mode 0000 0010 (02h) standby enter standby mode 0000 0100 (04h) reset reset the device 0000 0110 (06h) start start and restart (synchronize) conversions 0000 1000 (08h) stop stop conversion 0000 1010 (0ah) data read commands rdatac enable read data continuous mode. this mode is the default mode at power-up. (1) 0001 0000 (10h) sdatac stop read data continuously mode 0001 0001 (11h) rdata read data by command; supports multiple read back. 0001 0010 (12h) register read commands rreg read n nnnn registers starting at address r rrrr 001 r rrrr (2xh) (2) 000 n nnnn (2) wreg write n nnnn registers starting at address r rrrr 010 r rrrr (4xh) (2) 000 n nnnn (2) cs sclk drdy dout stat 24-bit 24-bit 24-bit 24-bit 24-bit 24-bit 24-bit 24-bit 24-bit ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8 216 sclks din 40 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.5.3.1 sending multi-byte commands the ads1299-x serial interface decodes commands in bytes and requires 4 t clk cycles to decode and execute. therefore, when sending multi-byte commands (such as rreg or wreg), a 4 t clk period must separate the end of one byte (or command) and the next. assuming clk is 2.048 mhz, then t sdecode (4 t clk ) is 1.96 s. when sclk is 16 mhz, one byte can be transferred in 500 ns. this byte transfer time does not meet the t sdecode specification; therefore, a delay must be inserted so the end of the second byte arrives 1.46 s later. if sclk is 4 mhz, one byte is transferred in 2 s. because this transfer time exceeds the t sdecode specification, the processor can send subsequent bytes without delay. in this later scenario, the serial port can be programmed to move from single-byte transfers per cycle to multiple bytes. 9.5.3.2 wakeup: exit standby mode the wakeup command exits low-power standby mode; see the standby: enter standby mode subsection of the spi command definitions section. time is required when exiting standby mode (see the electrical characteristics for details). there are no sclk rate restrictions for this command and can be issued at any time. any following commands must be sent after a delay of 4 t clk cycles. 9.5.3.3 standby: enter standby mode the standby command enters low-power standby mode. all parts of the circuit are shut down except for the reference section. the standby mode power consumption is specified in the electrical characteristics . there are no sclk rate restrictions for this command and can be issued at any time. do not send any other commands other than the wakeup command after the device enters standby mode. 9.5.3.4 reset: reset registers to default values the reset command resets the digital filter cycle and returns all register settings to default values. see the reset ( reset) subsection of the spi interface section for more details. there are no sclk rate restrictions for this command and can be issued at any time. 18 t clk cycles are required to execute the reset command. avoid sending any commands during this time. 9.5.3.5 start: start conversions the start command starts data conversions. tie the start pin low to control conversions by command. if conversions are in progress, this command has no effect. the stop command stops conversions. if the start command is immediately followed by a stop command, then there must be a 4-t clk cycle delay between them. when the start command is sent to the device, keep the start pin low until the stop command is issued. (see the start subsection of the spi interface section for more details.) there are no sclk rate restrictions for this command and can be issued at any time. 9.5.3.6 stop: stop conversions the stop command stops conversions. tie the start pin low to control conversions by command. when the stop command is sent, the conversion in progress completes and further conversions are stopped. if conversions are already stopped, this command has no effect. there are no sclk rate restrictions for this command and can be issued at any time. 9.5.3.7 rdatac: read data continuous the rdatac command enables conversion data output on each drdy without the need to issue subsequent read data commands. this mode places the conversion data in the output register and may be shifted out directly. the read data continuous mode is the device default mode; the device defaults to this mode on power- up. rdatac mode is cancelled by the stop read data continuous command. if the device is in rdatac mode, a sdatac command must be issued before any other commands can be sent to the device. there are no sclk rate restrictions for this command. however, subsequent data retrieval sclks or the sdatac command should wait at least 4 t clk cycles before completion (see the sending multi-byte commands section). rdatac timing is illustrated in figure 45 . as depicted in figure 45 , there is a keep out zone of 4 t clk cycles around the 41 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated drdy pulse where this command cannot be issued in. if no data are retrieved from the device, dout and drdy behave similarly in this mode. to retrieve data from the device after the rdatac command is issued, make sure either the start pin is high or the start command is issued. figure 45 shows the recommended way to use the rdatac command. rdatac is ideally-suited for applications such as data loggers or recorders, where registers are set one time and do not need to be reconfigured. (1) t update = 4 / f clk . do not read data during this time. figure 45. rdatac usage 9.5.3.8 sdatac: stop read data continuous the sdatac command cancels the read data continuous mode. there are no sclk rate restrictions for this command, but the next command must wait for 4 t clk cycles before completion. 9.5.3.9 rdata: read data the rdata command loads the output shift register with the latest data when not in read data continuous mode. issue this command after drdy goes low to read the conversion result. there are no sclk rate restrictions for this command, and there is no wait time needed for the subsequent commands or data retrieval sclks. to retrieve data from the device after the rdata command is issued, make sure either the start pin is high or the start command is issued. when reading data with the rdata command, the read operation can overlap the next drdy occurrence without data corruption. figure 46 shows the recommended way to use the rdata command. rdata is best suited for ecg- and eeg-type systems, where register settings must be read or changed often between conversion cycles. figure 46. rdata usage hi-z start drdy cs sclk din dout rdata status register+ 8-channel data (216 bits) rdata start drdy cs sclk din t update dout hi-z rdatac status register + 8-channel data (216 bits) next data 42 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.5.3.10 rreg: read from register this command reads register data. the register read command is a two-byte command followed by the register data output. the first byte contains the command and register address. the second command byte specifies the number of registers to read ? 1. first command byte: 001 r rrrr , where r rrrr is the starting register address. second command byte: 000 n nnnn , where n nnnn is the number of registers to read ? 1. the 17th sclk rising edge of the operation clocks out the msb of the first register, as shown in figure 47 . when the device is in read data continuous mode, an sdatac command must be issued before the rreg command can be issued. the rreg command can be issued any time. however, because this command is a multi-byte command, there are sclk rate restrictions depending on how the sclks are issued to meet the t sdecode timing. see the serial clock (sclk) subsection of the spi interface section for more details. note that cs must be low for the entire command. figure 47. rreg command example: read two registers starting from register 00h (id register) (byte 1 = 0010 0000, byte 2 = 0000 0001) 9.5.3.11 wreg: write to register this command writes register data. the register write command is a two-byte command followed by the register data input. the first byte contains the command and register address. the second command byte specifies the number of registers to write ? 1. first command byte: 010 r rrrr , where r rrrr is the starting register address. second command byte: 000 n nnnn , where n nnnn is the number of registers to write ? 1. after the command bytes, the register data follows (in msb-first format), as shown in figure 48 . the wreg command can be issued any time. however, because this command is a multi-byte command, there are sclk rate restrictions depending on how the sclks are issued to meet the t sdecode timing. see the serial clock (sclk) subsection of the spi interface section for more details. note that cs must be low for the entire command. figure 48. wreg command example: write two registers starting from 00h (id register) (byte 1 = 0100 0000, byte 2 = 0000 0001) 1 9 17 25 cs sclk din byte 1 byte 2 reg data 1 reg data 2 dout 1 9 17 25 cs sclk din byte 1 byte 2 dout reg data reg data + 1 43 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated (1) register or bit only available in the ads1299-6 and ads1299. register bits set to 0h or 00h in the ads1299-4. (2) register or bit only available in the ads1299. register bits set to 0h or 00h in the ads1299-4 and ads1299-6. 9.6 register maps table 11 describes the various ads1299-x registers. table 11. register assignments address register default setting register bits 7 6 5 4 3 2 1 0 read only id registers 00h id xxh rev_id[2:0] 1 dev_id[1:0] nu_ch[1:0] global settings across channels 01h config1 96h 1 daisy_en clk_en 1 0 dr[2:0] 02h config2 c0h 1 1 0 int_cal 0 cal_amp0 cal_freq[1:0] 03h config3 60h pd_refbuf 1 1 bias_meas biasref_int pd_bias bias_loff_ sens bias_stat 04h loff 00h comp_th[2:0] 0 ilead_off[1:0] flead_off[1:0] channel-specific settings 05h ch1set 61h pd1 gain1[2:0] srb2 mux1[2:0] 06h ch2set 61h pd2 gain2[2:0] srb2 mux2[2:0] 07h ch3set 61h pd3 gain3[2:0] srb2 mux3[2:0] 08h ch4set 61h pd4 gain4[2:0] srb2 mux4[2:0] 09h ch5set (1) 61h pd5 gain5[2:0] srb2 mux5[2:0] 0ah ch6set (1) 61h pd6 gain6[2:0] srb2 mux6[2:0] 0bh ch7set (2) 61h pd7 gain7[2:0] srb2 mux7[2:0] 0ch ch8set (2) 61h pd8 gain8[2:0] srb2 mux8[2:0] 0dh bias_sensp 00h biasp8 (2) biasp7 (2) biasp6 (1) biasp5 (1) biasp4 biasp3 biasp2 biasp1 0eh bias_sensn 00h biasn8 (2) biasn7 (2) biasn6 (1) biasn5 (1) biasn4 biasn3 biasn2 biasn1 0fh loff_sensp 00h loffp8 (2) loffp7 (2) loffp6 (1) loffp5 (1) loffp4 loffp3 loffp2 loffp1 10h loff_sensn 00h loffm8 (2) loffm7 (2) loffm6 (1) loffm5 (1) loffm4 loffm3 loffm2 loffm1 11h loff_flip 00h loff_flip8 (2) loff_flip7 (2) loff_flip6 (1) loff_flip5 (1) loff_flip4 loff_flip3 loff_flip2 loff_flip1 lead-off status registers (read-only registers) 12h loff_statp 00h in8p_off in7p_off in6p_off in5p_off in4p_off in3p_off in2p_off in1p_off 13h loff_statn 00h in8m_off in7m_off in6m_off in5m_off in4m_off in3m_off in2m_off in1m_off gpio and other registers 14h gpio 0fh gpiod[4:1] gpioc[4:1] 15h misc1 00h 0 0 srb1 0 0 0 0 0 16h misc2 00h 0 0 0 0 0 0 0 0 17h config4 00h 0 0 0 0 single_ shot 0 pd_loff_ comp 0 44 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1 user register description the read-only id control register is programmed during device manufacture to indicate device characteristics. 9.6.1.1 id: id control register (address = 00h) (reset = xxh) figure 49. id control register 7 6 5 4 3 2 1 0 rev_id[2:0] 1 dev_id[1:0] nu_ch[1:0] r-xh r-1h r-3h r-xh legend: r/w = read/write; r = read only; -n = value after reset table 12. id control register field descriptions bit field type reset description 7:5 rev_id[2:0] r xh reserved. these bits indicate the revision of the device and are subject to change without notice. 4 reserved r 1h reserved. always read 1. 3:2 dev_id[1:0] r 3h device identification. these bits indicates the device. 11 = ads1299-x 1:0 nu_ch[1:0] r xh number of channels. these bits indicates number of channels. 00 = 4-channel ads1299-4 01 = 6-channel ads1299-6 10 = 8-channel ads1299 45 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.2 config1: configuration register 1 (address = 01h) (reset = 96h) this register configures the daisy_en bit, clock, and data rate. figure 50. config1: configuration register 1 7 6 5 4 3 2 1 0 1 daisy_en clk_en 1 0 dr[2:0] r/w-1h r/w-0h r/w-0h r/w-2h r/w-6h legend: r/w = read/write; r = read only; -n = value after reset (1) additional power is consumed when driving external devices. table 13. configuration register 1 field descriptions bit field type reset description 7 reserved r/w 1h reserved always write 1h 6 daisy_en r/w 0h daisy-chain or multiple readback mode this bit determines which mode is enabled. 0 = daisy-chain mode 1 = multiple readback mode 5 clk_en r/w 0h clk connection (1) this bit determines if the internal oscillator signal is connected to the clk pin when the clksel pin = 1. 0 = oscillator clock output disabled 1 = oscillator clock output enabled 4:3 reserved r/w 2h reserved always write 2h 2:0 dr[2:0] r/w 6h output data rate these bits determine the output data rate of the device. f mod = f clk / 2. 000: f mod / 64 (16 ksps) 001: f mod / 128 (8 ksps) 010: f mod / 256 (4 ksps) 011: f mod / 512 (2 ksps) 100: f mod / 1024 (1 ksps) 101: f mod / 2048 (500 sps) 110: f mod / 4096 (250 sps) 111: reserved (do not use) 46 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.3 config2: configuration register 2 (address = 02h) (reset = c0h) this register configures the test signal generation. see the input multiplexer section for more details. figure 51. config2: configuration register 2 7 6 5 4 3 2 1 0 1 1 0 int_cal 0 cal_amp cal_freq[1:0] r/w-6h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 14. configuration register 2 field descriptions bit field type reset description 7:5 reserved r/w 6h reserved always write 6h 4 int_cal r/w 0h test source this bit determines the source for the test signal. 0 = test signals are driven externally 1 = test signals are generated internally 3 reserved r/w 0h reserved always write 0h 2 cal_amp r/w 0h test signal amplitude these bits determine the calibration signal amplitude. 0 = 1 ? (vrefp ? vrefn) / 2400 1 = 2 ? (vrefp ? vrefn) / 2400 1:0 cal_freq[1:0] r/w 0h test signal frequency these bits determine the calibration signal frequency. 00 = pulsed at f clk / 2 21 01 = pulsed at f clk / 2 20 10 = do not use 11 = at dc 47 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.4 config3: configuration register 3 (address = 03h) (reset = 60h) configuration register 3 configures either an internal or exteral reference and bias operation. figure 52. config3: configuration register 3 7 6 5 4 3 2 1 0 pd_refbuf 1 1 bias_meas biasref_int pd_bias bias_loff_ sens bias_stat r/w-0h r/w-3h r/w-0h r/w-0h r/w-0h r/w-0h r-0h legend: r/w = read/write; r = read only; -n = value after reset table 15. configuration register 3 field descriptions bit field type reset description 7 pd_refbuf r/w 0h power-down reference buffer this bit determines the power-down reference buffer state. 0 = power-down internal reference buffer 1 = enable internal reference buffer 6:5 reserved r/w 3h reserved always write 3h. 4 bias_meas r/w 0h bias measurement this bit enables bias measurement. the bias signal may be measured with any channel. 0 = open 1 = bias_in signal is routed to the channel that has the mux_setting 010 (v ref ) 3 biasref_int r/w 0h biasref signal this bit determines the biasref signal source. 0 = biasref signal fed externally 1 = biasref signal (avdd ? avss) / 2 generated internally 2 pd_bias r/w 0h bias buffer power this bit determines the bias buffer power state. 0 = bias buffer is powered down 1 = bias buffer is enabled 1 bias_loff_sens r/w 0h bias sense function this bit enables the bias sense function. 0 = bias sense is disabled 1 = bias sense is enabled 0 bias_stat r 0h bias lead-off status this bit determines the bias status. 0 = bias is connected 1 = bias is not connected 48 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.5 loff: lead-off control register (address = 04h) (reset = 00h) the lead-off control register configures the lead-off detection operation. figure 53. loff: lead-off control register 7 6 5 4 3 2 1 0 comp_th2[2:0] 0 ilead_off[1:0] flead_off[1:0] r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 16. lead-off control register field descriptions bit field type reset description 7:5 comp_th[2:0] r/w 0h lead-off comparator threshold comparator positive side 000 = 95% 001 = 92.5% 010 = 90% 011 = 87.5% 100 = 85% 101 = 80% 110 = 75% 111 = 70% comparator negative side 000 = 5% 001 = 7.5% 010 = 10% 011 = 12.5% 100 = 15% 101 = 20% 110 = 25% 111 = 30% 4 reserved r/w 0h reserved always write 0h. 3:2 ilead_off[1:0] r/w 0h lead-off current magnitude these bits determine the magnitude of current for the current lead-off mode. 00 = 6 na 01 = 12 na 10 = 6 a 11 = 24 a 1:0 flead_off[1:0] r/w 0h lead-off frequency these bits determine the frequency of lead-off detect for each channel. 00 = when any bits of the loff_sensp or loff_sensn registers are turned on, make sure that flead[1:0] are either set to 01 or 11 01 = ac lead-off detection at f dr / 4 10 = do not use 11 = dc lead-off detection turned on 49 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.6 ch nset: individual channel settings ( n = 1 to 8) (address = 05h to 0ch) (reset = 61h) the ch[1:8]set control register configures the power mode, pga gain, and multiplexer settings channels. see the input multiplexer section for details. ch[2:8]set are similar to ch1set, corresponding to the respective channels. figure 54. chnset: individual channel settings register 7 6 5 4 3 2 1 0 pd n gain n [2:0] srb2 mux n [2:0] r/w-0h r/w-6h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 17. individual channel settings ( n = 1 to 8) field descriptions bit field type reset description 7 pd n r/w 0h power-down this bit determines the channel power mode for the corresponding channel. 0 = normal operation 1 = channel power-down. when powering down a channel, ti recommends that the channel be set to input short by setting the appropriate muxn[2:0] = 001 of the chnset register. 6:4 gain n [2:0] r/w 6h pga gain these bits determine the pga gain setting. 000 = 1 001 = 2 010 = 4 011 = 6 100 = 8 101 = 12 110 = 24 111 = do not use 3 srb2 r/w 0h srb2 connection this bit determines the srb2 connection for the corresponding channel. 0 = open 1 = closed 2:0 mux n [2:0] r/w 1h channel input these bits determine the channel input selection. 000 = normal electrode input 001 = input shorted (for offset or noise measurements) 010 = used in conjunction with bias_meas bit for bias measurements. 011 = mvdd for supply measurement 100 = temperature sensor 101 = test signal 110 = bias_drp (positive electrode is the driver) 111 = bias_drn (negative electrode is the driver) 50 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.7 bias_sensp: bias drive positive derivation register (address = 0dh) (reset = 00h) this register controls the selection of the positive signals from each channel for bias voltage (bias) derivation. see the bias drive (dc bias circuit) section for details. registers bits[5:4] are not available for the ads1299-4. register bits[7:6] are not available for the ads1299-4, or ads1299-6. set unavailable bits for the associated device to 0 when writing to the register. figure 55. bias_sensp: bias positive signal derivation register 7 6 5 4 3 2 1 0 biasp8 biasp7 biasp6 biasp5 biasp4 biasp3 biasp2 biasp1 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 18. bias positive signal derivation field descriptions bit field type reset description 7 biasp8 r/w 0h in8p to bias route channel 8 positive signal into bias derivation 0: disabled 1: enabled 6 biasp7 r/w 0h in7p to bias route channel 7 positive signal into bias derivation 0: disabled 1: enabled 5 biasp6 r/w 0h in6p to bias route channel 6 positive signal into bias derivation 0: disabled 1: enabled 4 biasp5 r/w 0h in5p to bias route channel 5 positive signal into bias derivation 0: disabled 1: enabled 3 biasp4 r/w 0h in4p to bias route channel 4 positive signal into bias derivation 0: disabled 1: enabled 2 biasp3 r/w 0h in3p to bias route channel 3 positive signal into bias derivation 0: disabled 1: enabled 1 biasp2 r/w 0h in2p to bias route channel 2 positive signal into bias channel 0: disabled 1: enabled 0 biasp1 r/w 0h in1p to bias route channel 1 positive signal into bias channel 0: disabled 1: enabled 51 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.8 bias_sensn: bias drive negative derivation register (address = 0eh) (reset = 00h) this register controls the selection of the negative signals from each channel for bias voltage (bias) derivation. see the bias drive (dc bias circuit) section for details. registers bits[5:4] are not available for the ads1299-4. register bits[7:6] are not available for the ads1299-4, or ads1299-6. set unavailable bits for the associated device to 0 when writing to the register. figure 56. bias_sensn: bias negative signal derivation register 7 6 5 4 3 2 1 0 biasn8 biasn7 biasn6 biasn5 biasn4 biasn3 biasn2 biasn1 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 19. bias negative signal derivation field descriptions bit field type reset description 7 biasn8 r/w 0h in8n to bias route channel 8 negative signal into bias derivation 0: disabled 1: enabled 6 biasn7 r/w 0h in7n to bias route channel 7 negative signal into bias derivation 0: disabled 1: enabled 5 biasn6 r/w 0h in6n to bias route channel 6 negative signal into bias derivation 0: disabled 1: enabled 4 biasn5 r/w 0h in5n to bias route channel 5 negative signal into bias derivation 0: disabled 1: enabled 3 biasn4 r/w 0h in4n to bias route channel 4 negative signal into bias derivation 0: disabled 1: enabled 2 biasn3 r/w 0h in3n to bias route channel 3 negative signal into bias derivation 0: disabled 1: enabled 1 biasn2 r/w 0h in2n to bias route channel 2 negative signal into bias derivation 0: disabled 1: enabled 0 biasn1 r/w 0h in1n to bias route channel 1 negative signal into bias derivation 0: disabled 1: enabled 52 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.9 loff_sensp: positive signal lead-off detection register (address = 0fh) (reset = 00h) this register selects the positive side from each channel for lead-off detection. see the lead-off detection section for details. the loff_statp register bits are only valid if the corresponding loff_sensp bits are set to 1. registers bits[5:4] are not available for the ads1299-4. register bits[7:6] are not available for the ads1299-4, or ads1299-6. set unavailable bits for the associated device to 0 when writing to the register. figure 57. loff_sensp: positive signal lead-off detection register 7 6 5 4 3 2 1 0 loffp8 loffp7 loffp6 loffp5 loffp4 loffp3 loffp2 loffp1 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 20. positive signal lead-off detection field descriptions bit field type reset description 7 loffp8 r/w 0h in8p lead off enable lead-off detection on in8p 0: disabled 1: enabled 6 loffp7 r/w 0h in7p lead off enable lead-off detection on in7p 0: disabled 1: enabled 5 loffp6 r/w 0h in6p lead off enable lead-off detection on in6p 0: disabled 1: enabled 4 loffp5 r/w 0h in5p lead off enable lead-off detection on in5p 0: disabled 1: enabled 3 loffp4 r/w 0h in4p lead off enable lead-off detection on in4p 0: disabled 1: enabled 2 loffp3 r/w 0h in3p lead off enable lead-off detection on in3p 0: disabled 1: enabled 1 loffp2 r/w 0h in2p lead off enable lead-off detection on in2p 0: disabled 1: enabled 0 loffp1 r/w 0h in1p lead off enable lead-off detection on in1p 0: disabled 1: enabled 53 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.10 loff_sensn: negative signal lead-off detection register (address = 10h) (reset = 00h) this register selects the negative side from each channel for lead-off detection. see the lead-off detection section for details. the loff_statn register bits are only valid if the corresponding loff_sensn bits are set to 1. registers bits[5:4] are not available for the ads1299-4. register bits[7:6] are not available for the ads1299-4, or ads1299-6. set unavailable bits for the associated device to 0 when writing to the register. figure 58. loff_sensn: negative signal lead-off detection register 7 6 5 4 3 2 1 0 loffm8 loffm7 loffm6 loffm5 loffm4 loffm3 loffm2 loffm1 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 21. negative signal lead-off detection field descriptions bit field type reset description 7 loffm8 r/w 0h in8n lead off enable lead-off detection on in8n 0: disabled 1: enabled 6 loffm7 r/w 0h in7n lead off enable lead-off detection on in7n 0: disabled 1: enabled 5 loffm6 r/w 0h in6n lead off enable lead-off detection on in6n 0: disabled 1: enabled 4 loffm5 r/w 0h in5n lead off enable lead-off detection on in5n 0: disabled 1: enabled 3 loffm4 r/w 0h in4n lead off enable lead-off detectionn on in4n 0: disabled 1: enabled 2 loffm3 r/w 0h in3n lead off enable lead-off detectionion on in3n 0: disabled 1: enabled 1 loffm2 r/w 0h in2n lead off enable lead-off detectionction on in2n 0: disabled 1: enabled 0 loffm1 r/w 0h in1n lead off enable lead-off detectionction on in1n 0: disabled 1: enabled 54 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.11 loff_flip: lead-off flip register (address = 11h) (reset = 00h) this register controls the direction of the current used for lead-off derivation. see the lead-off detection section for details. figure 59. loff_flip: lead-off flip register 7 6 5 4 3 2 1 0 loff_flip8 loff_flip7 loff_flip6 loff_flip5 loff_flip4 loff_flip3 loff_flip2 loff_flip1 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 22. lead-off flip register field descriptions bit field type reset description 7 loff_flip8 r/w 0h channel 8 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 8 for lead-off detection. 0: no flip: in8p is pulled to avdd and in8n pulled to avss 1: flipped: in8p is pulled to avss and in8n pulled to avdd 6 loff_flip7 r/w 0h channel 7 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 7 for lead-off detection. 0: no flip: in7p is pulled to avdd and in7n pulled to avss 1: flipped: in7p is pulled to avss and in7n pulled to avdd 5 loff_flip6 r/w 0h channel 6 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 6 for lead-off detection. 0: no flip: in6p is pulled to avdd and in6n pulled to avss 1: flipped: in6p is pulled to avss and in6n pulled to avdd 4 loff_flip5 r/w 0h channel 5 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 5 for lead-off detection. 0: no flip: in5p is pulled to avdd and in5n pulled to avss 1: flipped: in5p is pulled to avss and in5n pulled to avdd 3 loff_flip4 r/w 0h channel 4 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 4 for lead-off detection. 0: no flip: in4p is pulled to avdd and in4n pulled to avss 1: flipped: in4p is pulled to avss and in4n pulled to avdd 2 loff_flip3 r/w 0h channel 3 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 3 for lead-off detection. 0: no flip: in3p is pulled to avdd and in3n pulled to avss 1: flipped: in3p is pulled to avss and in3n pulled to avdd 1 loff_flip2 r/w 0h channel 2 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 2 for lead-off detection. 0: no flip: in2p is pulled to avdd and in2n pulled to avss 1: flipped: in2p is pulled to avss and in2n pulled to avdd 0 loff_flip1 r/w 0h channel 1 loff polarity flip flip the pull-up or pull-down polarity of the current source on channel 1 for lead-off detection. 0: no flip: in1p is pulled to avdd and in1n pulled to avss 1: flipped: in1p is pulled to avss and in1n pulled to avdd 55 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.12 loff_statp: lead-off positive signal status register (address = 12h) (reset = 00h) this register stores the status of whether the positive electrode on each channel is on or off. see the lead-off detection section for details. ignore the loff_statp values if the corresponding loff_sensp bits are not set to 1. when the loff_sensep bits are 0, the loff_statp bits should be ignored. figure 60. loff_statp: lead-off positive signal status register (read-only) 7 6 5 4 3 2 1 0 in8p_off in7p_off in6p_off in5p_off in4p_off in3p_off in2p_off in1p_off r-0h r-0h r-0h r-0h r-0h r-0h r-0h r-0h legend: r/w = read/write; r = read only; -n = value after reset table 23. lead-off positive signal status field descriptions bit field type reset description 7 in8p_off r 0h channel 8 positive channel lead-off status status of whether in8p electrode is on or off 0: electrode is on 1: electrode is off 6 in7p_off r 0h channel 7 positive channel lead-off status status of whether in7p electrode is on or off 0: electrode is on 1: electrode is off 5 in6p_off r 0h channel 6 positive channel lead-off status status of whether in6p electrode is on or off 0: electrode is on 1: electrode is off 4 in5p_off r 0h channel 5 positive channel lead-off status status of whether in5p electrode is on or off 0: electrode is on 1: electrode is off 3 in4p_off r 0h channel 4 positive channel lead-off status status of whether in4p electrode is on or off 0: electrode is on 1: electrode is off 2 in3p_off r 0h channel 3 positive channel lead-off status status of whether in3p electrode is on or off 0: electrode is on 1: electrode is off 1 in2p_off r 0h channel 2 positive channel lead-off status status of whether in2p electrode is on or off 0: electrode is on 1: electrode is off 0 in1p_off r 0h channel 1 positive channel lead-off status status of whether in1p electrode is on or off 0: electrode is on 1: electrode is off 56 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.13 loff_statn: lead-off negative signal status register (address = 13h) (reset = 00h) this register stores the status of whether the negative electrode on each channel is on or off. see the lead-off detection section for details. ignore the loff_statn values if the corresponding loff_sensn bits are not set to 1. when the loff_sensen bits are 0, the loff_statp bits should be ignored. figure 61. loff_statn: lead-off negative signal status register (read-only) 7 6 5 4 3 2 1 0 in8n_off in7n_off in6n_off in5n_off in4n_off in3n_off in2n_off in1n_off r-0h r-0h r-0h r-0h r-0h r-0h r-0h r-0h legend: r/w = read/write; r = read only; -n = value after reset table 24. lead-off negative signal status field descriptions bit field type reset description 7 in8n_off r 0h channel 8 negative channel lead-off status status of whether in8n electrode is on or off 0: electrode is on 1: electrode is off 6 in7n_off r 0h channel 7 negative channel lead-off status status of whether in7n electrode is on or off 0: electrode is on 1: electrode is off 5 in6n_off r 0h channel 6 negative channel lead-off status status of whether in6n electrode is on or off 0: electrode is on 1: electrode is off 4 in5n_off r 0h channel 5 negative channel lead-off status status of whether in5n electrode is on or off 0: electrode is on 1: electrode is off 3 in4n_off r 0h channel 4 negative channel lead-off status status of whether in4n electrode is on or off 0: electrode is on 1: electrode is off 2 in3n_off r 0h channel 3 negative channel lead-off status status of whether in3n electrode is on or off 0: electrode is on 1: electrode is off 1 in2n_off r 0h channel 2 negative channel lead-off status status of whether in2n electrode is on or off 0: electrode is on 1: electrode is off 0 in1n_off r 0h channel 1 negative channel lead-off status status of whether in1n electrode is on or off 0: electrode is on 1: electrode is off 57 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.14 gpio: general-purpose i/o register (address = 14h) (reset = 0fh) the general-purpose i/o register controls the action of the three gpio pins. when resp_ctrl[1:0] is in mode 01 and 11, the gpio2, gpio3, and gpio4 pins are not available for use. figure 62. gpio: general-purpose i/o register 7 6 5 4 3 2 1 0 gpiod[4:1] gpioc[4:1] r/w-0h r/w-fh legend: r/w = read/write; r = read only; -n = value after reset table 25. general-purpose i/o field descriptions bit field type reset description 7:4 gpiod[4:1] r/w 0h gpio data these bits are used to read and write data to the gpio ports. when reading the register, the data returned correspond to the state of the gpio external pins, whether they are programmed as inputs or as outputs. as outputs, a write to the gpiod sets the output value. as inputs, a write to the gpiod has no effect. gpio is not available in certain respiration modes. 3:0 gpioc[4:1] r/w fh gpio control (corresponding gpiod) these bits determine if the corresponding gpiod pin is an input or output. 0 = output 1 = input 58 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.15 misc1: miscellaneous 1 register (address = 15h) (reset = 00h) this register provides the control to route the srb1 pin to all inverting inputs of the four, six, or eight channels (ads1299-4, ads1299-6, or ads1299). figure 63. misc1: miscellaneous 1 register 7 6 5 4 3 2 1 0 0 0 srb1 0 0 0 0 0 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 26. miscellaneous 1 register field descriptions bit field type reset description 7:6 reserved r/w 0h reserved always write 0h 5 srb1 r/w 0h stimulus, reference, and bias 1 this bit connects the srb1 to all 4, 6, or 8 channels inverting inputs 0 = switches open 1 = switches closed 4:0 reserved r/w 0h reserved always write 0h 9.6.1.16 misc2: miscellaneous 2 (address = 16h) (reset = 00h) this register is reserved for future use. figure 64. misc1: miscellaneous 1 register 7 6 5 4 3 2 1 0 0 0 0 0 0 0 0 0 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 27. miscellaneous 1 register field descriptions bit field type reset description 7:0 reserved r/w 0h reserved always write 0h 59 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 9.6.1.17 config4: configuration register 4 (address = 17h) (reset = 00h) this register configures the conversion mode and enables the lead-off comparators. figure 65. config4: configuration register 4 7 6 5 4 3 2 1 0 0 0 0 0 single_shot 0 pd_loff_ comp 0 r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h r/w-0h legend: r/w = read/write; r = read only; -n = value after reset table 28. configuration register 4 field descriptions bit field type reset description 7:4 reserved r/w 0h reserved always write 0h 3 single_shot r/w 0h single-shot conversion this bit sets the conversion mode. 0 = continuous conversion mode 1 = single-shot mode 2 reserved r/w 0h reserved always write 0h 1 pd_loff_comp r/w 0h lead-off comparator power-down this bit powers down the lead-off comparators. 0 = lead-off comparators disabled 1 = lead-off comparators enabled 0 reserved r/w 0h reserved always write 0h 60 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 10 applications and implementation note information in the following applications sections is not part of the ti component specification, and ti does not warrant its accuracy or completeness. ti ? s customers are responsible for determining suitability of components for their purposes. customers should validate and test their design implementation to confirm system functionality. 10.1 application information 10.1.1 unused inputs and outputs power down unused analog inputs and connect them directly to avdd. power down the bias amplifier if unused and float biasout and biasinv. biasin can also float or can be tied directly to avss if unused. tie biasref directly to avss or leave floating if unused. tie srb1 and srb2 directly to avss or leave them floating if unused. do not float unused digital inputs because excessive power-supply leakage current might result. set the two- state mode setting pins high to dvdd or low to dgnd through 10-k resistors. if not daisy-chaining devices, tie daisyin directly to dgnd. 10.1.2 setting the device for basic data capture figure 66 outlines the procedure to configure the device in a basic state and capture data. this procedure puts the device into a configuration that matches the parameters listed in the specifications section, in order to check if the device is working properly in the user system. follow this procedure initially until familiar with the device settings. after this procedure has been verified, the device can be configured as needed. for details on the timings for commands, see the appropriate sections in the data sheet. sample programming codes are added for the ecg and eeg-specific functions. 61 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated application information (continued) figure 66. initial flow at power-up set pdwn = 1 set reset = 1 wait > t por for power-on reset // delay for power-on reset and oscillator start-up // if start is tied high, after this step // drdy toggles at f clk / 8192 set clksel pin = 1 and wait for oscillator to wake up no // follow power-up sequencing external clock set clksel pin = 0 and provide external clock f clk = 2.048 mhz yes set pdb_refbuf = 1 and wait for internal reference to settle write certain registers, including input short set start = 1 // activate conversion // after this point drdy toggles at // f clk / 8192 // set device for dr = f mod / 4096 wreg config1 96h wreg config2 c0h // set all channels to input short wreg chnset 01h yes rdatac // put the device back in rdatac mode rdatac capture data and check noise // look for drdy and issue 24 + n x 24 sclks set test signals capture data and test signal // activate a (1 mv x v ref / 2.4) square-wave test signal // on all channels sdatac wreg config2 d0h wreg chnset 05h rdatac external reference // if using internal reference, send this command wreg config3 e0h no send sdatac command // device wakes up in rdatac mode, so send // sdatac command so registers can be written sdatac issue reset pulse, wait for 18 tclks // activate dut // cs can be either tied low or selectively // pulled low before sending commands and // data to the device or reading data from // the device analog and digital power-up // look for drdy and issue 24 + n x 24 sclks vcap1 ? 1.1 v no // if vcap1 < 1.1 v at t por , frqwlqxhzdlwlqjxqwlo9&$3? 1.1 v 62 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated application information (continued) 10.1.2.1 lead-off sample code to set dc lead-off with pull-up and pull-down resistors on all channels. wreg loff 0x13 // comparator threshold at 95% and 5%, pullup or pulldown resistor // dc lead-off wreg config4 0x02 // turn on dc lead-off comparators wreg loff_sensp 0xff // turn on the p-side of all channels for lead-off sensing wreg loff_sensn 0xff // turn on the n-side of all channels for lead-off sensing observe the status bits of the output data stream to monitor lead-off status. 10.1.2.2 bias drive sample code to choose bias as an average of the first three channels. wreg rld_sensp 0x07 // select channel 1-3 p-side for rld sensing wreg rld_sensn 0x07 // select channel 1-3 n-side for rld sensing wreg config3 b ? x1xx 1100 // turn on bias amplifier, set internal biasref voltage sample code to route the biasout signal through channel 4 n-side and measure bias with channel 5. make sure the external side to the chip biasout is connected to biasin. wreg config3 b ? xxx1 1100 // turn on bias amp, set internal biasref voltage, set bias measurement bit wreg ch4set b ? xxxx 0111 // route biasin to channel 4 n-side wreg ch5set b ? xxxx 0010 // route biasin to be measured at channel 5 w.r.t biasref 10.1.3 establishing the input common-mode the ads1299-x measures fully-differential signals where the common-mode voltage point is the midpoint of the positive and negative analog input. the internal pga restricts the common-mode input range because of the headroom required for operation. the human body is prone to common-mode drifts because noise easily couples onto the human body, similar to an antenna. these common-mode drifts may push the ads1299-x input common-mode voltage out of the measurable range of the adc. if a patient-drive electrode is used by the system, the ads1299-x includes an on-chip bias drive (bias) amplifier that connects to the patient drive electrode. the bias amplifier function is to bias the patient to maintain the other electrode common-mode voltages within the valid range. when powered on, the amplifier uses either the analog midsupply voltage, or the voltage present at the biasref pin, as a reference input to drive the patient to that voltage. the ads1299-x provides the option to use input electrode voltages as feedback to the amplifier to more effectively stabilize the output to the amplifier reference voltage by setting corresponding bits in the bias_sensp and bias_sensn registers. figure 67 shows an example of a three-electrode system that leverages this technique. figure 67. setting common-mode using bias electrode inxp inxn biasout biasinv 1 m ti device 1.5 nf antialiasing, protection antialiasing, protection protection electrode 1 electrode 2 bias electrode copyright ? 2016, texas instruments incorporated 63 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated application information (continued) 10.1.4 multiple device configuration the ads1299-x is designed to provide configuration flexibility when multiple devices are used in a system. the serial interface typically needs four signals: din, dout, sclk, and cs. with one additional chip select signal per device, multiple devices can be connected together. the number of signals needed to interface n devices is 3 + n . the bias drive amplifiers can be daisy-chained, as explained in the bias configuration with multiple devices section. to use the internal oscillator in a daisy-chain configuration, one device must be set as the master for the clock source with the internal oscillator enabled (clksel pin = 1) and the internal oscillator clock brought out of the device by setting the clk_en register bit to '1'. this master device clock is used as the external clock source for other devices. when using multiple devices, the devices can be synchronized with the start signal. the delay from start to the drdy signal is fixed for a given data rate (see the start subsection of the spi interface section for more details on the settling times). figure 68 shows the behavior of two devices when synchronized with the start signal. there are two ways to connect multiple devices with a optimal number of interface pins: cascade mode and daisy-chain mode. figure 68. synchronizing multiple converters 10.1.4.1 cascaded mode figure 69 a illustrates a configuration with two devices cascaded together. together, the devices create a system with 16 channels. dout, sclk, and din are shared. each device has its own chip select. when a device is not selected by the corresponding cs being driven to logic 1, the dout of this device is high-impedance. this structure allows the other device to take control of the dout bus. this configuration method is suitable for the majority of applications. start 1 device 1 clk drdy drdy 1 start clk start 2 device 2 clk drdy drdy 2 start clk drdy 1 drdy 2 64 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated application information (continued) 10.1.4.2 daisy-chain mode daisy-chain mode is enabled by setting the daisy_en bit in the config1 register. figure 69 b shows the daisy- chain configuration. in this mode sclk, din, and cs are shared across multiple devices. the dout of the second device is connected to the daisy_in of the first device, thereby creating a chain. when using daisy- chain mode, the multiple readback feature is not available. short the daisy_in pin to digital ground if not used. figure 2 describes the required timing for the device shown in the configurations of figure 69 . status and data from device 1 appear first on dout, followed by the status and data from device 2. the ads1299 can be daisy chained with a second ads1299, an ads1299-6, or an ads1299-4. (1) to reduce pin count, set the start pin low and use the start serial command to synchronize and start conversions. figure 69. multiple device configurations when all devices in the chain operate in the same register setting, din can be shared as well. this configuration reduces the spi communication signals to four, regardless of the number of devices. the bias driver cannot be shared among the multiple devices and an external clock must be used because the individual devices cannot be programmed when sharing a common din. note that from figure 2 , the sclk rising edge shifts data out of the device on dout. the sclk negative edge is used to latch data into the device daisy_in pin down the chain. this architecture allows for a faster sclk rate speed, but also makes the interface sensitive to board-level signal delays. the more devices in the chain, the more challenging adhering to setup and hold times becomes. a star-pattern connection of sclk to all devices, minimizing dout length, and other printed circuit board (pcb) layout techniques helps. placing delay circuits (such as buffers) between dout and daisy_in are ways to mitigate this challenge. one other option is to insert a d flip-flop between dout and daisy_in clocked on an inverted sclk. note also that daisy-chain mode requires some software overhead to recombine data bits spread across byte boundaries. figure 70 shows a timing diagram for this mode. figure 70. daisy-chain timing dout daisy_in 10 do tu 0 sclk msb 1 msb 0 2 1 3 216 217 218 msb 1 lsb 0 lsb 1 219 337 lsb 1 da a ft rom d ce 1 evi da a ft rom vide ce 2 start drdy cs sclk din dout device 1 start drdy cs sclk din dout device 2 start (1) a) standard configuration clkclk int gpo0 gpo1 sclkmosi host processor miso clk start drdy cs sclk din dout 0 device 1 start drdy cs sclk din daisy_in 1 device 2 start (1) b) daisy-chain configuration clkclk int gpo sclkmosi host processor miso clk 0 dout 1 daisy_in 0 65 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated application information (continued) the maximum number of devices that can be daisy-chained depends on the data rate at which the device is operated at. the maximum number of devices can be approximately calculated with equation 10 . where: n bits = device resolution (depending on data rate), and n channels = number of channels in the device. (10) for example, when the 8-channel ads1299 is operated at a 2-ksps data rate with a 4-mhz f sclk , 10 devices can be daisy-chained. 10.2 typical application the biopotential signals that are measured in electroencephalography (eeg) are small when compared to other types of biopotential signals. the ads1299 is equipped to measure such small signals due to its extremely low input-referred noise from its high performance internal pga. figure 71 and figure 72 are examples of how the ads1299 may be configured in typical eeg measurement setups. figure 71 shows how to measure electrode potentials in a sequential montage, whereas figure 72 illustrates referential montage measurement connections. figure 71. example schematic using the ads1299 in an eeg data acquisition application, sequential montage .. . in1p in1n biasinv biasout electrode 1 electrode 2 bias electrode .. . in2p in2n electrode 3 electrode 4 avdd avss +2.5 v -2.5 v + adc + + adc .. . .. . (avdd + avss)/2 biasref_int biasp1 biasn1 biasp2 biasn2 r filt r filt r filt r filt c filt c filt c f r f r p 220 k 220 k 220 k 220 k f sclk f (n )(n dr bits channels ) + 24 n = devices 66 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated typical application (continued) figure 72. example schematic using the ads1299 in an eeg data acquisition application, referential montage 10.2.1 design requirements table 29 shows the design requirements for a typical eeg measurement system. table 29. eeg data acquisition design requirements design parameter value bandwidth 1 hz - 50 hz minimum signal bandwidth 10 v pk input impedance > 10 m coupling dc 10.2.2 detailed design procedure each channel on the ads1299 is optimized to measure a separate eeg waveform. the specific connections depend on the eeg montage. the sequential montage is a configuration where each channel represents the voltage between two adjacent electrodes. for example, to measure the potential between electrode fp1 and f7 on channel 1 of the ads1299, route the fp1 electrode to in1p and the f7 electrode to in1n. the connections for a sequential montage are illustrated in figure 71 . .. . in1p in2p biasinv biasout electrode 1 electrode 2 bias electrode in3p in4p electrode 3 electrode 4 avdd avss +2.5 v -2.5 v srb1 reference electrode + adc + + adc .. . .. . (avdd + avss)/2 biasref_int biasp1 biasn1 biasp2 biasn2 220 k 220 k 220 k 220 k + adc + adc .. . srb1 biasp3 biasn3 biasp4 biasn4 220 k 220 k 220 k 220 k r filt r filt r filt r filt r filt c filt c filt c filt c filt c f r f r p 67 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated alternatively, eeg electrodes can be measured in a referential montage in which each of the electrodes is measured with respect to a single reference electrode . this montage also allows calculation of the waveforms that would have been measured in a sequential montage by finding the difference between two electrode waveforms which were measured with respect to the same electrode. the ads1299 allows for such a configuration through the use of the srb1 pin. the srb1 pin on the ads1299 may be internally routed to each channel negative input by setting the srb1 bit in the misc1 register. when the reference electrode is connected to the srb1 pin and all other electrodes are connected to the respective positive channel inputs, the electrode voltages can be measured with a referential montage. the referential montage is illustrated in figure 72 . see figure 18 for a diagram of the channel input multiplexer options. the ads1299 is designed to be an eeg front end such that no additional amplification or buffer stage is needed between the electrodes and ads1299. the ads1299 has a low-noise pga with excellent input-referred noise performance. for certain data rate and gain settings, the ads1299 introduces significantly less than 1 v rms of input-referred noise to the signal chain making the device more than capable of handling the 10- v pk minimum signal amplitude. ads1299 noise performance for different pga gains and data rate settings is listed in table 1 , table 2 , table 3 , and table 4 . traditional eeg data acquisition systems high-pass filter the signals in the front-end to remove dc signal content. this topology allows the signal to be amplified by a large gain so the signal can be digitized by a 12- to 16-bit adc. the ads1299 24-bit resolution allows the signal to be dc-coupled to the adc because small eeg signal information can be measured in addition to a significant dc offset. the ads1299 channel inputs have very low input bias current allowing electrodes to be connected to the inputs of the ads1299 with very little leakage current flowing on the patient cables. the ads1299 has a minimum dc input impedance of 1 g when the lead-off current sources are disabled and 500 m typically when the lead-off current sources are enabled. the passive components r filt and c filt form low-pass filters. in general, the filter is advised to be formed by using a differential capacitor c filt that shunts the inputs rather than individual rc filters whose capacitors shunt to ground. the differential capacitor configuration significantly improves common-mode rejection because this approach removes dependence on component mismatch. the cutoff frequency for the filter can be placed well past the data rate of the adc because of the delta-sigma adc filter-then-decimate topology. take care to prevent aliasing around the first repetition of the digital decimation filter response at f mod . assuming a 2.048-mhz f clk , f mod = 1.024 mhz. the value of r filt has a minimum set by technical standards for medical electronics. the capacitor value must be set to arrange the proper cutoff frequency. if the system is likely to be exposed to high-frequency emi, adding very small-value, common-mode capacitors to the inputs is advisable to filter high-frequency common-mode signals. if these capacitors are added, then the capacitors should be 10 or 20 times smaller than the differential capacitor to ensure their effect of cmrr is minimized. the integrated bias amplifier serves two purposes in an eeg data acquisition system with the ads1299. the bias amplifier provides a bias voltage that, when applied to the patient, keeps the measurement electrode common-mode voltage within the rails of the ads1299. this scenario allows for dc coupling. in addition, the bias amplifier can be configured to provide negative common-mode feedback to the patient to cancel unwanted common-mode signals appearing on the electrodes. this feature is especially helpful because biopotential acquisition systems are notoriously prone to mains-frequency common-mode interference. the bias amplifier is powered on by setting the pd_bias bit in the config3 register. set the biasref_int bit in the config3 register to input the internally generated analog mid-supply voltage the noninverting input of the bias amplifier. to enable an electrode as an input to the bias amplifier, set the corresponding bit in the bias_sensp or bias_sensn register. the dc gain of the bias amplifier is determined by r bias and the number of channel inputs enabled as inputs to the bias amplifier. the bias amplifier circuit only passes common-mode signals. therefore, the 330-k resistors at each pga output are in parallel for common-mode signals. the bias amplifier is configured in an inverting gain scheme. the formula for determining dc gain for common-mode signals input to the bias amplifier is shown in equation 11 . the capacitor c f sets the bandwidth for the bias amplifier. ensure that the amplifier has enough bandwidth to output all the intended common-mode signals. (11) out f in v r n v 330k u : 68 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated another advantage to a dc-coupled eeg data acquisition system is the ability to detect when an electrode no longer makes good contact with the patient. the ads1299 features integrated lead-off detection electronics. the lead-off detection section explains how to use the lead-off feature on the ads1299. note that when configured in a referential montage, only use one lead-off current source with the reference electrode. 10.2.3 application curves testing the capability of the ads1299 to measure signals in the band and near the amplitude of typical eeg signals can be done with a precision signal generator. the ads1299 was tested in a configuration like the one shown in figure 73 . figure 73. example schematic using the ads1299 in an eeg data acquisition application, referential montage the 952-k and 10.3-k resistors were used to attenuate the voltage from the signal source because the source could not reach the desired magnitude directly. with the voltage divider, the signal appearing at the inputs was a 3.5- v rms , 10-hz sine wave. figure 74 shows the input-referred conversion results from the ads1299 following calibration for offset. the signal that is measured is similar to some of the smallest extracranial eeg signals that can be measured with typical eeg acquisition systems. the signal can be clearly identified. given this measurement setup was a single-ended configuration without shielding, the measurement setup was subject to significant mains interference. a digital low-pass filter was applied to remove the interference. figure 74. ads1299 10-hz input signal results time (s) voltage ( p v) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -4.5 -3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 4.5 d001 inxp inxn avdd +2.5 v avss -2.5 v 4.99 k 4.7 nf 952 k 10.3 k 33 v rms 10 hz 69 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 11 power supply recommendations the ads1299-x has three power supplies: avdd, avdd1, and dvdd. for best performance, both avdd and avdd1 must be as quiet as possible. avdd1 provides the supply to the charge pump block and has transients at f clk . therefore, star connect avdd1 to the avdd pins and avss1 to the avss pins. avdd and avdd1 noise that is nonsynchronous with the ads1299-x operation must be eliminated. bypass each device supply with 10- f and 0.1- f solid ceramic capacitors. for best performance, place the digital circuits (dsp, microcontrollers, fpgas, and so forth) in the system so that the return currents on those devices do not cross the analog return path of the device. power the ads1299-x from unipolar or bipolar supplies. use surface-mount, low-cost, low-profile, multilayer ceramic-type capacitors for decoupling. in most cases, the vcap1 capacitor is also a multilayer ceramic; however, in systems where the board is subjected to high- or low- frequency vibration, install a nonferroelectric capacitor, such as a tantalum or class 1 capacitor (c0g or npo). eia class 2 and class 3 dielectrics such as (x7r, x5r, x8r, and so forth) are ferroelectric. the piezoelectric property of these capacitors can appear as electrical noise coming from the capacitor. when using internal reference, noise on the vcap1 node results in performance degradation. 11.1 power-up sequencing before device power up, all digital and analog inputs must be low. at the time of power up, keep all of these signals low until the power supplies have stabilized, as shown in figure 75 . allow time for the supply voltages to reach their final value, and then begin supplying the master clock signal to the clk pin. wait for time t por , then transmit a reset pulse using either the reset pin or reset command to initialize the digital portion of the chip. issue the reset after t por or after the vcap1 voltage is greater than 1.1 v, whichever time is longer. note that: ? t por is described in table 30 . ? the vcap1 pin charge time is set by the rc time constant set by the capacitor value on vcap1; see figure 24 . after releasing the reset pin, program the configuration registers. the power-up sequence timing is shown in table 30 . (1) timing to reset pulse is t por or after t bg , whichever is longer. (2) when using an external clock, t por timing does not start until clk is present and valid. figure 75. power-up timing diagram table 30. timing requirements for figure 75 min max unit t por wait after power up until reset 2 18 t clk t rst reset low duration 2 t clk 11.2 connecting the device to unipolar (5 v and 3.3 v) supplies figure 76 illustrates the ads1299-x connected to a unipolar supply. in this example, analog supply (avdd) is referenced to analog ground (avss) and digital supply (dvdd) is referenced to digital ground (dgnd). vcap1 supplies t por (1)(2) vcap = 1.1v 1.1v t bg (1) t rst 18 t clk start using device reset 70 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated connecting the device to unipolar (5 v and 3.3 v) supplies (continued) note: place the capacitors for supply, reference, and vcap1 to vcap4 as close to the package as possible. figure 76. single-supply operation 11.3 connecting the device to bipolar ( 2.5 v and 3.3 v) supplies figure 77 shows the ads1299-x connected to a bipolar supply. in this example, the analog supplies connect to the device analog supply (avdd). this supply is referenced to the device analog return (avss), and the digital supply (dvdd) is referenced to the device digital ground return (dgnd). note: place the capacitors for supply, reference, and vcap1 to vcap4 as close to the package as possible. figure 77. bipolar supply operation device 0.1 f m 1 f m avdd avdd1 0.1 f m 1 f m - 2.5 v avss avss1 dgnd dvdd +2.5 v +3.3 v 0.1 f m 1 f m vcap1 vcap2 vcap3 0.1 f m vrefp vrefn 10 f m vcap4 1 f m 1 f m 1 f m - 2.5 v 100 f m 0.1 f m resv1 device avdd 0.1 f m 1 f m +5 v avdd1 avss avss1 dgnd dvdd +3.3 v 0.1 f m 1 f m 0.1 f m vrefp vrefn vcap1vcap2 vcap3 vcap4 1 f m 1 f m 1 f m 10 f m 100 f m 0.1 f m resv1 71 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 12 layout 12.1 layout guidelines ti recommends employing best design practices when laying out a printed-circuit board (pcb) for both analog and digital components. this recommendation generally means that the layout separates analog components [such as adcs, amplifiers, references, digital-to-analog converters (dacs), and analog muxs] from digital components [such as microcontrollers, complex programmable logic devices (cplds), field-programmable gate arrays (fpgas), radio frequency (rf) transceivers, universal serial bus (usb) transceivers, and switching regulators]. an example of good component placement is shown in figure 78 . although figure 78 provides a good example of component placement, the best placement for each application is unique to the geometries, components, and pcb fabrication capabilities employed. that is, there is no single layout that is perfect for every design and careful consideration must always be used when designing with any analog component. figure 78. system component placement the following outlines some basic recommendations for the layout of the ads1299-x to get the best possible performance of the adc. a good design can be ruined with a bad circuit layout. ? separate analog and digital signals. to start, partition the board into analog and digital sections where the layout permits. route digital lines away from analog lines. this configuration prevents digital noise from coupling back into analog signals. ? the ground plane can be split into an analog plane (agnd) and digital plane (dgnd), but is not necessary. place digital signals over the digital plane, and analog signals over the analog plane. as a final step in the layout, the split between the analog and digital grounds must be connected together at the adc. ? fill void areas on signal layers with ground fill. ? provide good ground return paths. signal return currents flow on the path of least impedance. if the ground plane is cut or has other traces that block the current from flowing right next to the signal trace, then the current must find another path to return to the source and complete the circuit. if current is forced into a longer path, the chances that the signal radiates increases. sensitive signals are more susceptible to emi interference. ? use bypass capacitors on supplies to reduce high-frequency noise. do not place vias between bypass capacitors and the active device. placing the bypass capacitors on the same layer as close to the active device yields the best results. ? analog inputs with differential connections must have a capacitor placed differentially across the inputs. the differential capacitors must be of high quality. the best ceramic chip capacitors are c0g (npo), which have stable properties and low noise characteristics. 12.2 layout guidelines as with any precision circuit, careful pcb layout ensures the best performance. short, direct interconnections must be made and stray wiring capacitance must be avoided ? particularly at the analog input pins and avss. these analog input pins are high-impedance and extremely sensitive to extraneous noise. the avss pin must be treated as a sensitive analog signal and connected directly to the supply ground with proper shielding. leakage currents between the pcb traces can exceed the input bias current of the ads1299-x if shielding is not implemented. keep digital signals as far as possible from the analog input signals on the pcb. device microcontroller signal conditioning (rc filters and amplifiers) supply generation connector or antenna ground fill or ground plane optional: split ground cut ground fill or ground plane optional: split ground cut interface transceiver ground fill or ground plane ground fill or ground plane 72 ads1299 , ads1299-4 , ads1299-6 sbas499b ? july 2012 ? revised october 2016 www.ti.com product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 12.3 layout example figure 79 is an example layout of the ads1299 requiring a minimum of two pcb layers. the example circuit is shown for either a single analog supply or a bipolar-supply connection. in this example, polygon pours are used as supply connections around the device. if a three- or four-layer pcb is used, the additional inner layers can be dedicated to route power traces. the pcb is partitioned with analog signals routed from the left, digital signals routed to the right, and power routed above and below the device. figure 79. ads1299 example layout ads1299 1: in8n 2: in8p 3: in7n 4: in7p 5: in6n 6: in6p 7: in5n 8: in5p 9: in4n 10: in4p 11: in3n 12: in3p 13: in2n 14: in2p 15: in1n 16: in1p 17: srb1 18: srb2 19: avdd 20: avss 21: avdd 22: avdd 23: avss 24: vrefp 25: vrefn 26: vcap4 27: nc 28: vcap1 29: nc 30: vcap2 31: resv1 32: avss 48: dvdd 47: drdy 46: gpio4 45: gpio3 44: gpio2 43: dout 42: gpio1 41: daisy_ in 40: sclk 39: cs 38: start 37: clk 36: reset 35:pwdn 34: din 33: dgnd 64: reserved 63: biasout 62: biasin 61: biasinv 60: biasref 59: avdd 58: avss 57: avss 56: avdd 55: vcap3 54: avdd1 53: avss1 52: clksel 51: dgnd 50: dvdd 49: dgnd reference, vcap, and power supply decoupling capacitors close to pins input filtered with differential capacitors via to avss pour or plane via to digital ground pour or plane long digital input lines terminated with resistors to prevent reflection 73 ads1299 , ads1299-4 , ads1299-6 www.ti.com sbas499b ? july 2012 ? revised october 2016 product folder links: ads1299 ads1299-4 ads1299-6 submit documentation feedback copyright ? 2012 ? 2016, texas instruments incorporated 13 device and documentation support 13.1 documentation support 13.1.1 related documentation for related documentation see the following: ? ads129x low-power, 8-channel, 24-bit analog front-end for biopotential measurements (sbas459) ? ref50xx low-noise, very low drift, precision voltage reference (sbos410) ? improving common-mode rejection using the right-leg drive amplifier application report (sbaa188) ? ads1299eeg-fe eeg front-end performance demonstration kit (slau443) 13.2 receiving notification of documentation updates to receive notification of documentation updates, navigate to the device product folder on ti.com. in the upper right corner, click on alert me to register and receive a weekly digest of any product information that has changed. for change details, review the revision history included in any revised document. 13.3 community resources the following links connect to ti community resources. linked contents are provided "as is" by the respective contributors. they do not constitute ti specifications and do not necessarily reflect ti's views; see ti's terms of use . ti e2e ? online community ti's engineer-to-engineer (e2e) community. created to foster collaboration among engineers. at e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. design support ti's design support quickly find helpful e2e forums along with design support tools and contact information for technical support. 13.4 trademarks e2e is a trademark of texas instruments. all other trademarks are the property of their respective owners. 13.5 electrostatic discharge caution this integrated circuit can be damaged by esd. texas instruments recommends that all integrated circuits be handled with appropriate precautions. failure to observe proper handling and installation procedures can cause damage. esd damage can range from subtle performance degradation to complete device failure. precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. 13.6 glossary slyz022 ? ti glossary . this glossary lists and explains terms, acronyms, and definitions. 14 mechanical, packaging, and orderable information the following pages include mechanical, packaging, and orderable information. this information is the most current data available for the designated devices. this data is subject to change without notice and revision of this document. for browser-based versions of this data sheet, refer to the left-hand navigation. package option addendum www.ti.com 5-nov-2016 addendum-page 1 packaging information orderable device status (1) package type package drawing pins package qty eco plan (2) lead/ball finish (6) msl peak temp (3) op temp (c) device marking (4/5) samples ads1299-4pag preview tqfp pag 64 160 green (rohs & no sb/br) cu nipdau level-3-260c-168 hr -40 to 85 ads1299-4 ads1299-4pagr preview tqfp pag 64 1500 green (rohs & no sb/br) cu nipdau level-3-260c-168 hr -40 to 85 ads1299-4 ads1299-6pag preview tqfp pag 64 160 green (rohs & no sb/br) cu nipdau level-3-260c-168 hr -40 to 85 ads1299-6 ads1299-6pagr preview tqfp pag 64 1500 green (rohs & no sb/br) cu nipdau level-3-260c-168 hr -40 to 85 ads1299-6 ads1299ipag active tqfp pag 64 160 green (rohs & no sb/br) cu nipdau level-3-260c-168 hr -40 to 85 ads1299 ADS1299IPAGR active tqfp pag 64 1500 green (rohs & no sb/br) cu nipdau level-3-260c-168 hr -40 to 85 ads1299 (1) the marketing status values are defined as follows: active: product device recommended for new designs. lifebuy: ti has announced that the device will be discontinued, and a lifetime-buy period is in effect. nrnd: not recommended for new designs. device is in production to support existing customers, but ti does not recommend using this part in a new design. preview: device has been announced but is not in production. samples may or may not be available. obsolete: ti has discontinued the production of the device. (2) eco plan - the planned eco-friendly classification: pb-free (rohs), pb-free (rohs exempt), or green (rohs & no sb/br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. tbd: the pb-free/green conversion plan has not been defined. pb-free (rohs): ti's terms "lead-free" or "pb-free" mean semiconductor products that are compatible with the current rohs requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. where designed to be soldered at high temperatures, ti pb-free products are suitable for use in specified lead-free processes. pb-free (rohs exempt): this component has a rohs exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. the component is otherwise considered pb-free (rohs compatible) as defined above. green (rohs & no sb/br): ti defines "green" to mean pb-free (rohs compatible), and free of bromine (br) and antimony (sb) based flame retardants (br or sb do not exceed 0.1% by weight in homogeneous material) (3) msl, peak temp. - the moisture sensitivity level rating according to the jedec industry standard classifications, and peak solder temperature. (4) there may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) multiple device markings will be inside parentheses. only one device marking contained in parentheses and separated by a "~" will appear on a device. if a line is indented then it is a continuation of the previous line and the two combined represent the entire device marking for that device. package option addendum www.ti.com 5-nov-2016 addendum-page 2 (6) lead/ball finish - orderable devices may have multiple material finish options. finish options are separated by a vertical ruled line. lead/ball finish values may wrap to two lines if the finish value exceeds the maximum column width. important information and disclaimer: the information provided on this page represents ti's knowledge and belief as of the date that it is provided. ti bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. efforts are underway to better integrate information from third parties. ti has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. ti and ti suppliers consider certain information to be proprietary, and thus cas numbers and other limited information may not be available for release. in no event shall ti's liability arising out of such information exceed the total purchase price of the ti part(s) at issue in this document sold by ti to customer on an annual basis. tape and reel information *all dimensions are nominal device package type package drawing pins spq reel diameter (mm) reel width w1 (mm) a0 (mm) b0 (mm) k0 (mm) p1 (mm) w (mm) pin1 quadrant ads1299-6pagr tqfp pag 64 1500 330.0 24.4 13.0 13.0 1.5 16.0 24.0 q2 ADS1299IPAGR tqfp pag 64 1500 330.0 24.4 13.0 13.0 1.5 16.0 24.0 q2 package materials information www.ti.com 5-nov-2016 pack materials-page 1 *all dimensions are nominal device package type package drawing pins spq length (mm) width (mm) height (mm) ads1299-6pagr tqfp pag 64 1500 367.0 367.0 45.0 ADS1299IPAGR tqfp pag 64 1500 367.0 367.0 45.0 package materials information www.ti.com 5-nov-2016 pack materials-page 2 mechanical data mtqf006a january 1995 revised december 1996 post office box 655303 ? dallas, texas 75265 pag (s-pqfp-g64) plastic quad flatpack 0,13 nom 0,25 0,45 0,75 seating plane 0,05 min 4040282 / c 11/96 gage plane 33 0,17 0,27 16 48 1 7,50 typ 49 64 sq 9,80 1,05 0,95 11,80 12,20 1,20 max 10,20 sq 17 32 0,08 0,50 m 0,08 0 7 notes: a. all linear dimensions are in millimeters. b. this drawing is subject to change without notice. c. falls within jedec ms-026 important notice texas instruments incorporated and its subsidiaries (ti) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per jesd46, latest issue, and to discontinue any product or service per jesd48, latest issue. buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. all semiconductor products (also referred to herein as ? components ? ) are sold subject to ti ? s terms and conditions of sale supplied at the time of order acknowledgment. ti warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in ti ? s terms and conditions of sale of semiconductor products. testing and other quality control techniques are used to the extent ti deems necessary to support this warranty. except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. ti assumes no liability for applications assistance or the design of buyers ? products. buyers are responsible for their products and applications using ti components. to minimize the risks associated with buyers ? products and applications, buyers should provide adequate design and operating safeguards. ti does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which ti components or services are used. information published by ti regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from ti under the patents or other intellectual property of ti. reproduction of significant portions of ti information in ti data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. ti is not responsible or liable for such altered documentation. information of third parties may be subject to additional restrictions. resale of ti components or services with statements different from or beyond the parameters stated by ti for that component or service voids all express and any implied warranties for the associated ti component or service and is an unfair and deceptive business practice. ti is not responsible or liable for any such statements. buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of ti components in its applications, notwithstanding any applications-related information or support that may be provided by ti. buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. buyer will fully indemnify ti and its representatives against any damages arising out of the use of any ti components in safety-critical applications. in some cases, ti components may be promoted specifically to facilitate safety-related applications. with such components, ti ? s goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. nonetheless, such components are subject to these terms. no ti components are authorized for use in fda class iii (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. only those ti components which ti has specifically designated as military grade or ? enhanced plastic ? are designed and intended for use in military/aerospace applications or environments. buyer acknowledges and agrees that any military or aerospace use of ti components which have not been so designated is solely at the buyer ' s risk, and that buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. ti has specifically designated certain components as meeting iso/ts16949 requirements, mainly for automotive use. in any case of use of non-designated products, ti will not be responsible for any failure to meet iso/ts16949. products applications audio www.ti.com/audio automotive and transportation www.ti.com/automotive amplifiers amplifier.ti.com communications and telecom www.ti.com/communications data converters dataconverter.ti.com computers and peripherals www.ti.com/computers dlp ? products www.dlp.com consumer electronics www.ti.com/consumer-apps dsp dsp.ti.com energy and lighting www.ti.com/energy clocks and timers www.ti.com/clocks industrial www.ti.com/industrial interface interface.ti.com medical www.ti.com/medical logic logic.ti.com security www.ti.com/security power mgmt power.ti.com space, avionics and defense www.ti.com/space-avionics-defense microcontrollers microcontroller.ti.com video and imaging www.ti.com/video rfid www.ti-rfid.com omap applications processors www.ti.com/omap ti e2e community e2e.ti.com wireless connectivity www.ti.com/wirelessconnectivity mailing address: texas instruments, post office box 655303, dallas, texas 75265 copyright ? 2016, texas instruments incorporated |
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