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w wm8728 24-bit, 192khz stereo dac with volume control wolfson microelectronics plc to receive regular email updates, sign up at http://www.wolfsonmicro.com/enews/ production data, august 2008, rev 4.6 copyright ? 2008 wolfson microelectronics plc description the wm8728 is a high performance stereo dac designed for audio applications such as dvd, home theatre systems, and digital tv. the wm8728 supports pcm data input word lengths from 16 to 32-bits and sampling rates up to 192khz. the wm8728 consists of a serial interface port, digital interpolation filters, multi-bit sigma delta modulators and stereo dac in a small 20-lead ssop package. the wm8728 also includes a digitally controllable mute and attenuate function for each channel. the wm8728 supports a variety of connection schemes for audio dac control. the 2 or 3-wire mpu serial port provides access to a wide range of features including on-chip mute, attenuation and phase reversal. a hardware controllable interface is also available the wm8728 is an ideal device to interface to ac-3 ? , dts ? , and mpeg audio decoders for surround sound applications, or for use in dvd players supporting dvd-a. features ? stereo dac with 24 bit pcm ? audio performance - 106db snr (?a? weighted @ 48khz) dac - -97db thd ? dac sampling frequency: 8khz - 192khz ? 2 or 3-wire serial control interface or hardware control ? programmable audio data interface modes - i 2 s, left, right justified, dsp - 16/20/24/32 bit word lengths ? independent digital volume control on each channel with 127.5db range in 0.5db steps ? 3.0v - 5.5v supply operation ? 20-lead ssop package ? exceeds dolby class a performance requirements applications ? dvd-audio and dvd ?universal? players ? home theatre systems ? digital tv ? digital broadcast receivers block diagram
wm8728 production data w pd, rev 4.6, august 2008 2 table of contents description ............................................................................................................1 features..................................................................................................................1 applications ..........................................................................................................1 block diagram ......................................................................................................1 table of contents ..............................................................................................2 pin configuration................................................................................................3 ordering information .......................................................................................3 pin description .....................................................................................................4 absolute maximum ratings..............................................................................5 dc electrical characteristics .....................................................................6 electrical characteristics ...........................................................................6 terminology ................................................................................................................. 7 master clock timing .................................................................................................. 8 digital audio interface ............................................................................................ 8 power supply timing ................................................................................................. 9 power on reset (por) ............................................................................................... 9 mpu 3-wire interface timing ..................................................................................12 mpu 2-wire interface timing ..................................................................................13 device description ............................................................................................14 introduction ...............................................................................................................14 clocking schemes .....................................................................................................14 digital audio interface ...........................................................................................15 audio data sampling rates.....................................................................................17 hardware control modes .....................................................................................18 software control interface...............................................................................20 register map ...............................................................................................................21 attenuation control...............................................................................................22 digital filter characteristics.............................................................................25 dac filter responses...............................................................................................25 digital de-emphasis characteristics ........................................................26 applications information ..............................................................................27 recommended external components (pcm audio).........................................27 recommended external components values .................................................27 recommended analogue low pass filter for pcm data format (optional)..................................................................................................................... .28 package dimensions .........................................................................................29 important notice ...............................................................................................30 address: ....................................................................................................................... .30
wm8728 production data w pd, rev 4.6 august 2008 3 pin configuration ordering information device temp. range package moisture sensitivity level peak soldering temp wm8728seds/v -40 to +85 o c 20-lead ssop (pb-free) msl2 260 c wm8728seds/rv -40 to +85 o c 20-lead ssop (pb-free, tape and reel) msl2 260 c note: reel quantity = 2,000
wm8728 production data w pd, rev 4.6, august 2008 4 pin description pin name type description 1 lrcin digital input dac sample rate clock input: pcm input mode 2 din digital input serial audio data input: pcm input mode 3 bckin digital input audio data bit clock input 4 mclk digital input master clock input 5 zero digital output (open drain) infinite zero detect flag (l = izd detected, h = izd not detected). 6 dgnd supply digital ground supply 7 dvdd supply digital positive supply 8 voutr analogue output right channel dac output 9 agnd supply analogue ground supply 10 avdd supply analogue positive supply 11 voutl analogue output left channel dac output 12 vmid analogue output mid rail decoupling point 13 vrefn supply dac negative reference ? normally agnd, must not be below agnd 14 vrefp supply dac positive reference ? normally avdd, must not be above avdd 15 csbiwl digital input (pull-up) software mode: 3-wire serial control chip select hardware mode: input word length 16 mode digital input (pull-down) control mode selection (l = hardware, h = software) 17 muteb digital bi-directional mute control (l = mute on, h = mute off, z = automute enabled) 18 sdidem digital bi-directional software mode: 3 or 2-wire serial control data input: hardware mode: de-emphasis select 19 sck digital input (pull-down) software mode: 3 or 2-wire serial control clock input 20 lati2s digital input (pull-up) software mode 3-wire serial control load input hardware mode: input data format selection note: digital input pins have schmitt trigger input buffers.
wm8728 production data w pd, rev 4.6 august 2008 5 absolute maximum ratings absolute maximum ratings are stress ratings only. permanent damage to the device may be caused by continuously operating at or beyond these limits. device functional operating limits and guaranteed performance specifications are given under electrical characteristics at the test conditions specified. esd sensitive device. this device is manufactured on a cmos process. it is therefore generically susceptible to damage from excessive static voltages. proper esd precautions must be taken during handling and storage of this device. wolfson tests its package types according to ipc/jedec j-std-020b for moisture sensitivity to determine acceptable storage conditions prior to surface mount assembly. these levels are: msl1 = unlimited floor life at <30 c / 85% relative humidity. not normally stored in moisture barrier bag. msl2 = out of bag storage for 1 year at <30 c / 60% relative humidity. supplied in moisture barrier bag. msl3 = out of bag storage for 168 hours at <30 c / 60% relative humidity. supplied in moisture barrier bag. the moisture sensitivity level for each package type is specified in ordering information. condition min max digital supply voltage -0.3v +7v analogue supply voltage -0.3v +7v voltage range digital inputs dgnd -0.3v dvdd +0.3v voltage range analogue inputs agnd -0.3v avdd +0.3v master clock frequency 50mhz operating temperature range, t a -40 c +85 c storage temperature after soldering -65 c +150 c note: analogue and digital grounds must always be within 0.3v of each other.
wm8728 production data w pd, rev 4.6, august 2008 6 dc electrical characteristics parameter symbol test conditions min typ max unit digital supply range dvdd 3.0 5.5 v analogue supply range avdd 3.0 5.5 v ground agnd, dgnd 0 v difference dgnd to agnd -0.3 0 +0.3 v analogue supply current avdd = 5v 19 ma digital supply current dvdd = 5v 8 ma analogue supply current avdd = 3.3v 18 ma digital supply current dvdd = 3.3v 4 ma note: dvdd supply needs to be active before avdd supply for correct device power on reset. see power supply timing section. electrical characteristics test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit digital logic levels (ttl levels) input low level v il 0.8 v input high level v ih 2.0 v output low v ol i ol = 1ma dgnd + 0.3v v output high v oh i oh = 1ma dvdd ? 0.3v v analogue reference levels reference voltage vmid (vrefp - vrefn)/2 - 50mv (vrefp - vrefn)/2 (vrefp - vrefn)/2 + 50mv v potential divider resistance r vmid 10k ? dac output (load = 10k ? 50pf) 0dbfs full scale output voltage at dac outputs 1.1 x avdd/5 vrms snr (note 1,2,3) a-weighted, @ fs = 48khz 100 106 db snr (note 1,2,3) a-weighted @ fs = 96khz 106 db snr (note 1,2,3) a-weighted @ fs = 192khz 106 db snr (note 1,2,3) a-weighted, @ fs = 48khz avdd, dvdd = 3.3v 102 db snr (note 1,2,3) a-weighted @ fs = 96khz avdd, dvdd = 3.3v 102 db snr (note 1,2,3) non ?a? weighted @ fs = 48khz 103 db thd (note 1,2,3) 1khz, 0dbfs -97 db thd+n (dynamic range, note 2) 1khz, -60dbfs 100 106 db dac channel separation 100 db
wm8728 production data w pd, rev 4.6 august 2008 7 test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit analogue output levels load = 10k ? , 0dbfs 1.1 v rms output level load = 10k ? , 0dbfs, (avdd = 3.3v) 0.726 v rms gain mismatch channel-to-channel 1 %fsr to midrail or a.c. coupled 1 k ? minimum resistance load to midrail or a.c. coupled (avdd = 3.3v) 600 ohms maximum capacitance load 5v or 3.3v 100 pf output d.c. level (vrefp - vrefn)/2 v power on reset (por) por threshold 2.4 v notes: 1. ratio of output level with 1khz full scale input, to the output level with all zeros into the digital input, over a 20hz to 20khz bandwidth. 2. all performance measurements done with 20khz low pass filter, and where noted an a-weight filter. failure to use such a filter will result in higher thd+n and lower snr and dynamic range readings than are found in the electrical characteristics. the low pass filter removes out of band noise; although it is not audible it may affect dynamic specification values. 3. vmid decoupled with 10uf and 0.1uf capacitors (smaller values may result in reduced performance). terminology 1. signal-to-noise ratio (db) - snr is a measure of the difference in level between the full-scale output and the output with a zero signal applied. (no auto-zero or automute function is employed in achieving these results). 2. dynamic range (db) - dnr is a measure of the difference between the highest and lowest portions of a signal. normally a thd+n measurement at 60db below full scale. the measured signal is then corrected by adding the 60db to it. (e.g. thd+n @ -60db= -32db, dr= 92db). 3. thd+n (db) - thd+n is a ratio, of the rms values, of (noise + distortion)/signal. 4. stop band attenuation (db) - is the degree to which the frequency spectrum is attenuated (outside audio band). 5. channel separation (db) - also known as cross talk. this is a measure of the amount one channel is isolated from the other. normally measured by sending a full-scale signal down one channel and measuring the other.
wm8728 production data w pd, rev 4.6, august 2008 8 master clock timing mclk t mclkl t mclkh t mclky figure 1 master clock timing requirements test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit master clock timing information mclk master clock pulse width high t mclkh 13 ns mclk master clock pulse width low t mclkl 13 ns mclk master clock cycle time t mclky 26 ns mclk duty cycle 40:60 60:40 digital audio interface bckin lrcin t bch t bcl t bcy din t lrsu t ds t lrh t dh figure 2 digital audio data timing test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit audio data input timing information bckin cycle time t bcy 40 ns bckin pulse width high t bch 16 ns bckin pulse width low t bcl 16 ns lrcin set-up time to bckin rising edge t lrsu 8 ns lrcin hold time from bckin rising edge t lrh 8 ns din set-up time to bckin rising edge t ds 8 ns din hold time from bckin rising edge t dh 8 ns
wm8728 production data w pd, rev 4.6 august 2008 9 power supply timing figure 3 power supply timing requirements test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit power supply input timing information dvdd set up time to avdd rising edge t psu measured from dvdd=+2.4v to avdd=+0.7v 100 s power on reset (por) the wm8728 has an internal power-on-reset (por) circuit which is used to reset the digital logic into a default state after power up. a block diagram of the reset circuit is shown in figure 4 figure 4 block diagram of power-on-reset circuit
wm8728 production data w pd, rev 4.6, august 2008 10 the por circuit requires that the dvdd is applied before the avdd. the active low reset signal npor will be asserted low until vmid rises to 1.2v. when this threshold has been reached, then the npor is released and the digital interface has been reset. this is illustrated in the diagram shown in figure 5. figure 5 npor generation at power on reset
wm8728 production data w pd, rev 4.6 august 2008 11 figure 6 and figure 7 illustrate the npor generation when the avdd and dvdd power are removed. figure 6 illustrates the removal of dvdd before avdd. figure 7 illustrates the removal of avdd before avdd. dvdd avdd vmid npor normal operation mode reset 1.0v (typ) figure 6 npor generation at power-off reset (dvdd falls before avdd) dvdd avdd vmid normal operation mode reset npor falls with avdd npor 1.0v (typ) figure 7 npor generation at power-off reset (avdd falls before dvdd)
wm8728 production data w pd, rev 4.6, august 2008 12 mpu 3-wire interface timing figure 8 program register input timing - 3-wire serial control mode test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit program register input information sck rising edge to lati2s rising edge t scs 40 ns sck pulse cycle time t scy 80 ns sck pulse width low t scl 20 ns sck pulse width high t sch 20 ns sdidem to sck set-up time t dsu 20 ns sck to sdidem hold time t dho 20 ns lati2s pulse width low t csl 20 ns lati2s pulse width high t csh 20 ns lati2s rising to sck rising t css 20 ns csbiwl to lati2s set-up time t cssu 20 ns lati2s to csbiwl hold time t cssh 20 ns
wm8728 production data w pd, rev 4.6 august 2008 13 mpu 2-wire interface timing figure 9 program register input timing - 2-wire serial control mode test conditions avdd, dvdd = 5v, agnd = 0v, dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit program register input information sck pulse cycle time t scy 80 ns sck pulse width low t scl 20 ns sck pulse width high t sch 20 ns sdidem to sck data set-up time for start signal t ssu 10 ns sdidem from sck data hold time for start signal t shd 10 ns sdidem to sck data set-up time t dsu 20 ns sck to sdidem data hold time t dhd 20 ns sck rise time t scr 5 ns sck fall time t scf 5 ns sdidem rise time t dr 5 ns sdidem fall time t df 5 ns sdidem to sck data set-up time for stop signal t esu 10 ns notes: 1. the address for the device in the 2-wire mode is 001101x (binary) with the last bit selectable. 2. in the two-wire interface mode, the csbiwl pin indicates the final bit of the chip address. 3. in 2-wire mode the lati2s pin should be tied to either dgnd or dvss to avoid noise toggling the interface into 3-wire mode.
wm8728 production data w pd, rev 4.6, august 2008 14 device description introduction the wm8728 is a high performance dac designed for digital consumer audio applications. its range of features makes it ideally suited for use in dvd players, av receivers and other high-end consumer audio equipment. wm8728 is a complete 2-channel stereo audio digital-to-analogue converter, including digital interpolation filter, multi-bit sigma delta with dither, switched capacitor multi-bit stereo dac and output smoothing filters. the wm8728 includes an on-chip digital volume control, configurable digital audio interface and a 2 or 3 wire mpu control interface. it is fully compatible and an ideal partner for a range of industry standard microprocessors, controllers and dsps. control of internal functionality of the device is by either hardware control (pin programmed) or software control (2 or 3-wire serial control interface). the mode pin selects between hardware and software control. the software control interface may be asynchronous to the audio data interface. in which case control data will be re-synchronised to the audio processing internally. operation using a master clock of 256fs, 384fs, 512fs or 768fs is provided, selection between clock rates being automatically controlled in hardware mode, or serial controlled when in software mode. sample rates (fs) from less than 8ks/s to 96ks/s are allowed, provided the appropriate master clock is input. support is also provided for up to 192ks/s using a master clock of 128fs or 192fs. the audio data interface supports right justified, left justified and i 2 s (philips left justified, one bit delayed) interface formats along with a highly flexible dsp serial port interface. when in hardware mode, the three serial interface pins become control pins to allow selection of, input data format type (i 2 s or right justified), input word length (20 or 24 bit) and de-emphasis functions. the device is packaged in a small 20-pin ssop. clocking schemes in a typical digital audio system there is only one central clock source producing a reference clock to which all audio data processing is synchronised. this clock is often referred to as the audio system?s master clock. the external master system clock can be applied directly through the mclk input pin with no software configuration necessary for sample rate selection. note that on the wm8728, mclk is used to derive clocks for the dac path. the dac path consists of dac sampling clock, dac digital filter clock and dac digital audio interface timing. in a system where there are a number of possible sources for the reference clock it is recommended that the clock source with the lowest jitter be used to optimise the performance of the dac. wm8728 always acts as a slave and requires clocks to be inputs.
wm8728 production data w pd, rev 4.6 august 2008 15 digital audio interface audio data is applied to the internal dac filters via the digital audio interface. five popular interface formats are supported: ? left justified mode ? right justified mode ? i 2 s mode ? dsp mode a ? dsp mode b all five formats send the msb first and support word lengths of 16, 20, 24 and 32 bits with the exception that 32 bit data is not supported in right justified mode. din and lrcin maybe configured to be sampled on the rising or falling edge of bckin. in left justified, right justified and i 2 s modes, the digital audio interface receives data on the din input. audio data is time multiplexed with lrcin indicating whether the left or right channel is present. lrcin is also used as a timing reference to indicate the beginning or end of the data words. the minimum number of bckins per lrcin period is 2 times the selected word length. lrcin must be high for a minimum of word length bckins and low for a minimum of word length bckins. any mark to space ratio on lrcin is acceptable provided the above requirements are met the wm8728 will automatically detect when data with a lrcin period of exactly 32 bckins is sent, and select 16-bit mode - overriding any previously programmed word length. word length will revert to a programmed value only if a lrcin period other than 32 bckins is detected. in dsp mode a or b, the data is time multiplexed onto din. lrcin is used as a frame sync signal to identify the msb of the first word. the minimum number of bckins per lrcin period is 2 times the selected word length. any mark to space ratio is acceptable on lrcin provided the rising edge is correctly positioned. (see figure 13 and figure 14) left justified mode in left justified mode, the msb is sampled on the first rising edge of bckin following a lrcin transition. lrcin is high during the left data word and low during the right data word. left channel right channel lrcin bckin din 1/fs n 3 2 1 n-2 n-1 lsb msb n 3 2 1 n-2 n-1 lsb msb figure 10 left justified mode timing diagram
wm8728 production data w pd, rev 4.6, august 2008 16 right justified mode in right justified mode, the lsb is sampled on the rising edge of bckin preceding a lrcin transition. lrcin is high during the left data word and low during the right data word. left channel right channel lrcin bckin din 1/fs n 3 2 1 n-2 n-1 lsb msb n 3 2 1 n-2 n-1 lsb msb figure 11 right justified mode timing diagram i 2 s mode in i 2 s mode, the msb is sampled on the second rising edge of bckin following a lrcin transition. lrcin is low during the left data word and high during the right data word. left channel right channel lrcin bckin din 1/fs n 3 2 1 n-2 n-1 lsb msb n 3 2 1 n-2 n-1 lsb msb 1 bckin 1 bckin figure 12 i 2 s mode timing diagram dsp mode a in dsp mode a, the first bit is sampled on the bckin rising edge following the one that detects a low to high transition on lrcin. no bckin edges are allowed between the data words. the word order is din left, din right. lrcin bckin din input word length (iwl) 1/fs left channel n 2 1 n-1 lsb msb n 2 1 n-1 right channel no valid data 1 bckin 1 bckin figure 13 dsp mode a timing diagram
wm8728 production data w pd, rev 4.6 august 2008 17 dsp mode b in dsp mode b, the first bit is sampled on the bckin rising edge, which detects a low to high transition on lrcin. no bckin edges are allowed between the data words. the word order is din left, din right. lrcin bckin din input word length (iwl) 1/fs left channel n 2 1 n-1 lsb msb n 2 1 n-1 right channel no valid data 1 figure 14 dsp mode b timing diagram audio data sampling rates the master clock for wm8728 can range from 128fs to 768fs, where fs is the audio sampling frequency (lrcin) typically 32khz, 44.1khz, 48khz, 96khz or 192khz. the master clock is used to operate the digital filters and the noise shaping circuits. the wm8728 has a master clock detection circuit that automatically determines the relationship between the master clock frequency and the sampling rate (to within +/- 32 system clocks). if there is a greater than 32 clocks error, the interface shuts down the dac and mutes the output. the master clock should be synchronised with lrcin, although the wm8728 is tolerant of phase differences or jitter on this clock. see table 1 master clock frequency (mhz) (mclk) sampling rate (lrcin) 128fs 192fs 256fs 384fs 512fs 768fs 32khz 4.096 6.144 8.192 12.288 16.384 24.576 44.1khz 5.6448 8.467 11.2896 16.9340 22.5792 33.8688 48khz 6.114 9.216 12.288 18.432 24.576 36.864 96khz 12.288 18.432 24.576 36.864 unavailable unavailable 192khz 24.576 36.864 unavailable unavailable unavailable unavailable table 1 typical relationships between master clock frequency and sampling rate
wm8728 production data w pd, rev 4.6, august 2008 18 hardware control modes when the mode pin is held low, the following hardware modes of operation are available. mute and automute operation in both hardware and software modes, pin 17 (muteb) controls the selection of mute directly, and can be used to enable and disable the automute function. automute is enabled by leaving muteb pin floating, it is disabled by applying a signal to the pin. when left floating this pin becomes an output and indicates infinite zero detect (izd), see also pin 5 (zero). the status of izd controls the selection of mute when automute is enabled. when izd is detected mute is enabled and when izd is not detected mute is disabled. muteb pin description 0 mute dac channels 1 normal operation floating muteb becomes an output to indicate when izd occurs. l=izd detected (mute enabled), h=izd not detected (mute disabled). table 2 mute and automute control zero pin description 0 indicates infinite zero detected from the digital input. 1 indicates infinite zero not detected from the digital input. table 3 zero pin output figure 15 shows the application and release of mute whilst a full amplitude sinusoid is being played at 48khz sampling rate. when mute (lower trace) is asserted, the output (upper trace) begins to decay exponentially from the dc level of the last input sample. the output will decay towards v mid with a time constant of approximately 64 input samples. when mute is de- asserted, the output will restart almost immediately from the current input sample. -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 0 0.001 0.002 0.003 0.004 0.005 0.006 time(s) figure 15 application and release of soft mute the muteb pin is an input to select mute or not mute. muteb is active low; taking the pin low causes the filters to soft mute, ramping down the audio signal over a few milliseconds. taking muteb high again allows data into the filter.
wm8728 production data w pd, rev 4.6 august 2008 19 the automute function detects a series of zero value audio samples of 1024 samples long being applied to both channels. after such an event, a latch is set whose output (automuted) is wire or?ed through a 10kohm resistor to the muteb pin. thus if the muteb pin is not being driven, the automute function will assert mute. if muteb is tied high, automuted is overridden and will not mute unless the izd register bit is set. if muteb is driven from a bi-directional source, then both mute and automute functions are available. if muteb is not driven, automuted appears as a weak output (10kohm-source impedance) so can be used to drive external mute circuits. automuted will be removed as soon as any channel receives a non-zero input. a diagram showing how the various mute modes interact is shown below figure 16. izd (register bit) automuted (internal signal) 10k ? mut (register bit) softmute (internal signal) muteb pin figure 16 selection logic for mute modes input format selection in hardware mode, lati2s (pin 20) and csbiwl (pin 15) become input controls for selection of input data format type and input data word length. lati2s csbiwl input data mode 0 0 24-bit right justified 0 1 20-bit right justified 1 0 16-bit i 2 s 1 1 24-bit i 2 s table 4 input format selection note: in 24 bit i 2 s mode, any width of 24 bits or less is supported provided that lrcin is high for a minimum of 24 bckins and low for a minimum of 24 bckins. if exactly 32 bckins occur in one lrcin (16 high, 16 low) the chip will auto detect and run a 16 bit data mode. de-emphasis control in hardware mode, sdidem (pin 18) becomes an input control for selection of de-emphasis filtering to be applied. sdidem de-emphasis 0 off 1 on table 5 de-emphasis control
wm8728 production data w pd, rev 4.6, august 2008 20 software control interface the software control interface may be operated using a 2-wire interface compatible or 3-wire (spi- compatible) interface. selection of control mode the wm8728 may be programmed to operate in hardware or software control modes. this is achieved by setting the state of the mode pin. mode interface format 0 hardware control mode 1 software control mode table 6 control interface mode selection 3-wire (spi compatible) serial control mode in this mode, sdidem is used for the program data, sck is used to clock in the program data and lati2s is used to latch in the program data. the 3-wire interface protocol is shown in figure 17. figure 17 3-wire serial interface notes: 1. b[15:9] are control address bits 2. b[8:0] are control data bits 3. csbiwl needs to be low during writes ? see figure 8 2-wire serial control mode in 2-wire mode, which is the default, sdidem is used for the program data and sck is used to clock in the program data see figure 18. wm8728 has an address of 001101x (binary) which represents an audio device. the final address digit is dependent on pin csbiwl, which should be tied to either dvdd or dgnd. this allows the device to have a choice of two identification header addresses used in the 2 wire interface word. this feature allows more than one wm8728 device to be present on the interface bus. lati2s should be tied to either dvdd or dgnd, as it is unused. this pin if toggled from low to high and high to low, will cause the device to enter the 3-wire interface mode and cannot be placed back into 2-wire mode except by toggling the mode pin, or powering off the device. figure 18 2-wire serial interface
wm8728 production data w pd, rev 4.6 august 2008 21 register map wm8728 uses a total of 4 program registers, which are 16-bits long. these registers are all loaded through input pin sdidem. using either 2-wire or 3-wire serial control mode as shown figure 8 and figure 9 b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 m0 0 0 0 0 0 0 0 updatel lat7 lat6 lat5 lat4 lat3 lat2 lat1 lat0 m1 0 0 0 0 0 0 1 updater rat7 rat6 rat5 rat4 rat3 rat2 rat1 rat0 m2 0 0 0 0 0 1 0 0 0 0 iw2 iw1 iw0 pwdn deemph mut m3 0 0 0 0 0 1 1 izd 0 0 bcp rev 0 atc lrp i 2 s address data table 7 mapping of program registers register address (a3,a2,a1,a0) bits name default description [7:0] lat[7:0] 11111111 (0db) attenuation data for left channel in 0.5db steps, see table 10 0000 dacl attenuation 8 updatel 0 attenuation data load control for left channel. 0: store dacl in intermediate latch (no change to output) 1: store dacl and update attenuation on both channels. [7:0] rat[7:0] 11111111 (0db) attenuation data for right channel in 0.5db steps, see table 10 0001 dacr attenuation 8 updater 0 attenuation data load control for right channel. 0: store dacr in intermediate latch (no change to output) 1: store dacr and update attenuation on both channels. 0 mut 0 left and right dacs soft mute control. 0: no mute 1: mute 1 deemph 0 de-emphasis control. 0: de-emphasis off 1: de-emphasis on 2 pwdn 0 left and right dacs power-down control 0: all dacs running, output is active 1: all dacs in power saving mode, output muted 0010 dac control [5:3] iw[2:0] 0 audio data format select, see table 15 0 i 2 s 0 audio data format select, see table 15 1 lrp 0 polarity select for lrcin/dsp mode select. 0: normal lrcin polarity/dsp late mode 1: inverted lrcin polarity/dsp early mode 2 atc 0 attenuator control. 0: all dacs use attenuation as programmed. 1: right channel dacs use corresponding left dac attenuation 4 rev 0 output phase reverse. 5 bcp 0 bckin polarity 0 : normal bckin polarity 1: inverted bckin polarity 0011 interface control 8 izd 0 infinite zero detection circuit control and automute control 0: infinite zero detect disabled 1: infinite zero detect enabled table 8 register bit descriptions
wm8728 production data w pd, rev 4.6, august 2008 22 attenuation control each dac channel can be attenuated digitally before being applied to the digital filter. attenuation is 0db by default but can be set between 0 and 127.5db in 0.5db steps using the 8 attenuation control bits. all attenuation registers are double latched allowing new values to be pre-latched to both channels before being updated synchronously. setting the update bit on any attenuation write will cause all pre-latched values to be immediately applied to the dac channels. register address bits label default description [7:0] lat[7:0] 11111111 (0db) attenuation data for left channel dacl in 0.5db steps. 0000 attenuation dacl 8 updatel 0 controls simultaneous update of all attenuation latches 0: store dacl in intermediate latch (no change to output) 1: store dacl and update attenuation on all channels. [7:0] rat[7:0] 11111111 (0db) attenuation data for right channel dacr in 0.5db steps. 0001 attenuation dacr 8 updater 0 controls simultaneous update of all attenuation latches 0: store dacr in intermediate latch (no change to output) 1: store dacr and update attenuation on all channels. table 9 attenuation register map note: 1. the update bit is not latched. if update=0, the attenuation value will be written to the pre-latch but not applied to the relevant dac. if update=1, all pre-latched values and the current value being written will be applied on the next input sample. 2. care should be used in reducing the attenuation as rapid large volume changes can introduce zipper noise. dac output attenuation registers lat and rat control the left and right channel attenuation. table 9 shows how the attenuation levels are selected from the 8-bit words. xat[7:0] attenuation level 00(hex) db (mute) 01(hex) 127db : 126.5 db : : : : fe(hex) 0.5db ff(hex) 0db table 10 attenuation control levels mute modes setting the mut register bit will apply a 'soft' mute to the input of the digital filters: register address bit label default description 0010 dac control 0 mut 0 soft mute select 0 : normal operation 1: soft mute all channels table 11 mute control
wm8728 production data w pd, rev 4.6 august 2008 23 de-emphasis mode setting the deemph register bit puts the digital filters into de-emphasis mode: register address bit label default description 0010 dac control 1 deemph 0 de-emphasis mode select: 0 : de-emphasis off 1: de-emphasis on table 12 de-emphasis control powerdown mode setting the pwdn register bit immediately connects all outputs to v mid and selects a low power mode. all trace of the previous input samples is removed, and all control register settings are cleared. when pwdn is cleared again the first 16 input samples will be ignored, as the fir will repeat it's power-on initialisation sequence. register address bit label default description 0010 dac control 2 pwdn 0 power down mode select: 0 : normal mode 1: power down mode table 13 powerdown control digital audio interface control registers the wm8728 has a fully featured digital audio interface that is a superset of that contained in the wm8716. interface format is selected via the iwl[2:0] register bits in register m2 and the i 2 s register bit in m3. register address bit label default description 0010 dac control 5:3 iwl[2:0] 000000 interface format select 0011 interface control 0 i 2 s 0 interface format select table 14 interface format controls iw2 i 2 s iw1 iw0 audio interface description (note 1) 0 0 0 0 16 bit right justified mode 0 0 0 1 20 bit right justified mode 0 0 1 0 24 bit right justified mode 0 0 1 1 24 bit left justified mode 0 1 0 0 16 bit i 2 s mode 0 1 0 1 24 bit i 2 s mode 0 1 1 0 20 bit i 2 s mode 0 1 1 1 20 bit left justified mode 1 0 0 0 16 bit dsp mode 1 0 0 1 20 bit dsp mode 1 0 1 0 24 bit dsp mode 1 0 1 1 32 bit dsp mode 1 1 0 0 16 bit left justified mode table 15 audio data input format note: in all modes, the data is signed 2's complement. the digital filters always input 24-bit data. if the dac is programmed to receive 16 or 20 bit data, the wm8728 pads the unused lsbs with zeros. if the dac is programmed into 32-bit mode, the 8 lsbs are treated as zero.
wm8728 production data w pd, rev 4.6, august 2008 24 selection of lrcin polarity in left justified, right justified or i 2 s modes, the lrp register bit controls the polarity of lrcin. if this bit is set high, the expected polarity of lrcin will be the opposite of that shown in figure 10, figure 11 and figure 12. note that if this feature is used as a means of swapping the left and right channels, a 1 sample phase difference will be introduced. register address bit label default description 0011 interface control 1 lrp 0 lrcin polarity (normal) 0 : normal lrcin polarity 1: inverted lrcin polarity table 16 lrcin polarity control in dsp modes, the lrcin register bit is used to select between early and late modes (see figure 13 and figure 14. register address bit label default description 0011 interface control 1 lrp 0 dsp format (dsp modes) 0 : late dsp mode 1: early dsp mode table 17 dsp format control in dsp early mode, the first bit is sampled on the bckin rising edge following the one that detects a low to high transition on lrcin. in dsp late mode, the first bit is sampled on the bckin rising edge, which detects a low to high transition on lrcin. no bckin edges are allowed between the data words. the word order is din left, din right. attenuator control mode setting the atc register bit causes the left channel attenuation settings to be applied to both left and right channel dacs from the next audio input sample. no update to the attenuation registers is required for atc to take effect. register address bit label default description 0011 interface control 2 atc 0 attenuator control mode: 0 : right channels use right attenuation 1: right channels use left attenuation table 18 attenuation control select output phase reversal the rev register bit controls the phase of the output signal. setting the rev bit causes the phase of the output signal to be inverted. register address bit label default description 0011 interface control 4 rev 0 analogue output phase 0: normal 1: inverted table 19 output phase control bckin polarity by default, lrcin and din are sampled on the rising edge of bckin and should ideally change on the falling edge. data sources which change lrcin and din on the rising edge of bckin can be supported by setting the bcp register bit. setting bcp to 1 inverts the polarity of bckin to the inverse of that shown in figure 10, figure 11, figure 12, figure 13 and figure 14. register address bit label default description 0011 interface control 5 bcp 0 bckin polarity 0 : normal bckin polarity 1: inverted bckin polarity table 20 bckin polarity control
wm8728 production data w pd, rev 4.6 august 2008 25 infinite zero detection setting the izd register bit determines whether the device is automuted when a sequence of more than 1024 zeros is detected. register address bit label default description 0011 interface control 8 izd 0 infinite zero detection circuit control and automute control 0: infinite zero detect disabled 1: infinite zero detect enabled table 21 izd control digital filter characteristics parameter symbol test conditions min typ max unit passband edge -3db 0.487fs passband ripple f < 0.444fs 0.05 db stopband attenuation f > 0.555fs -60 db table 22 digital filter characteristics dac filter responses -120 -100 -80 -60 -40 -20 0 0 0.5 1 1.5 2 2.5 3 response (db) frequency (fs) figure 19 dac digital filter frequency response -44.1, 48 and 96khz -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 response (db) frequency (fs) figure 20 dac digital filter ripple -44.1, 48 and 96khz -80 -60 -40 -20 0 0 0.2 0.4 0.6 0.8 1 response (db) frequency (fs) figure 21 dac digital filter frequency response -192khz -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 response (db) frequency (fs) figure 22 dac digital filter ripple -192khz
wm8728 production data w pd, rev 4.6, august 2008 26 digital de-emphasis characteristics -10 -8 -6 -4 -2 0 0 2 4 6 8 10 12 14 16 response (db) frequency (khz) figure 23 de-emphasis frequency response (32khz) -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 0 2 4 6 8 10 12 14 16 response (db) frequency (khz) figure 24 de-emphasis error (32khz) -10 -8 -6 -4 -2 0 0 5 10 15 20 response (db) frequency (khz) figure 25 de-emphasis frequency response (44.1khz) -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0 5 10 15 20 response (db) frequency (khz) figure 26 de-emphasis error (44.1khz) -10 -8 -6 -4 -2 0 0 5 10 15 20 response (db) frequency (khz) figure 27 de-emphasis frequency response (48khz) -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 0 5 10 15 20 response (db) frequency (khz) figure 28 de-emphasis error (48khz)
wm8728 production data w pd, rev 4.6 august 2008 27 applications information recommended external components (pcm audio) figure 29 external components diagram recommended external components values component reference suggested value description c1 and c5 10 f de-coupling for dvdd and avdd/vrefp c2 to c4 0.1 f de-coupling for dvdd and avdd/vrefp c6 and c7 10 f output ac coupling caps to remove midrail dc level from outputs. c8 0.1 f c9 10 f reference de-coupling capacitors for vmid pin. c10 10 f filtering for vrefp. omit if avdd low noise. r1 10k ? 10k pull-up to dvdd r2 33 ? filtering for vrep. use 0 ? if avdd low noise. table 23 external components description
wm8728 production data w pd, rev 4.6, august 2008 28 recommended analogue low pass filter for pcm data format (optional) + _ + +vs -vs 10uf 51 ? 7.5k ? 680pf 1.8k ? 47k ? 4.7k ? 4.7k ? 1.0nf figure 30 recommended low pass filter (optional)
wm8728 production data w pd, rev 4.6 august 2008 29 package dimensions notes: a. all linear dimensions are in millimeters. b. this drawing is subject to change without notice. c. body dimensions do not include mold flash or protrusion, not to exceed 0.20mm. d. meets jedec.95 mo-150, variation = ae. refer to this specification for further details. dm0015.c ds: 20 pin ssop (7.2 x 5.3 x 1.75 mm) symbols dimensions (mm) min nom max a ----- ----- 2.0 a 1 0.05 ----- ----- a 2 1.65 1.75 1.85 b 0.22 0.30 0.38 c 0.09 ----- 0.25 d 6.90 7.20 7.50 e 0.65 bsc e 7.40 7.80 8.20 5.00 5.30 5.60 l 0.55 0.75 0.95 ref: a a2 a1 seating plane -c- 0.10 c 10 1 d 11 20 e b e1 e - jedec.95, mo 150 0 o 4 o 8 o e 1 l 1 1.25 ref c l gauge plane 0.25 l 1
wm8728 production data w pd, rev 4.6, august 2008 30 important notice wolfson microelectronics plc (?wolfson?) products and services are sold subject to wolfson?s terms and conditions of sale, delivery and payment supplied at the time of order acknowledgement. wolfson warrants performance of its products to the specifications in effect at the date of shipment. wolfson reserves the righ t to make changes to its products and specifications or to discontinue any product or service without notice. customers should therefore obtain the latest version of relevant information from wolfson to verify that the information is current. testing and other quality control techniques are utilised to the extent wolfson deems necessary to support its warranty. specific testing of all parameters of each device is not necessarily performed unless required by law or regulation. in order to minimise risks associated with customer applications, the customer must use adequate design and operating safeguards to minimise inherent or procedural hazards. wolfson is not liable for applications assistance or customer product design. the customer is solely responsible for its selection and use of wolfson products. wolfson is not liable for such selection or use nor for use of any circuitry other than circuitry entirely embodied in a wolfson product. wolfson?s products are not intended for use in life support systems, appliances, nuclear systems or systems where malfunction can reasonably be expected to result in personal injury, death or severe property or environmental damage. any use of products by the customer for such purposes is at the customer?s own risk. wolfson does not grant any licence (express or implied) under any patent right, copyright, mask work right or other intellectua l property right of wolfson covering or relating to any combination, machine, or process in which its products or services might be or are used. any provision or publication of any third party?s products or services does not constitute wolfson?s approval, licence, warranty or endorsement thereof. any third party trade marks contained in this document belong to the respective thir d party owner. reproduction of information from wolfson datasheets is permissible only if reproduction is without alteration and is accompanied by all associated copyright, proprietary and other notices (including this notice) and conditions. wolfson is not liable for any unauthorised alteration of such information or for any reliance placed thereon. any representations made, warranties given, and/or liabilities accepted by any person which differ from those contained in this datasheet or in wolfson?s standard terms and conditions of sale, delivery and payment are made, given and/or accepted at that person?s own risk. wolfson is not liable for any such representations, warranties or liabilities or for any reliance placed the reon by any person. address: wolfson microelectronics plc westfield house 26 westfield road edinburgh eh11 2qb united kingdom tel :: +44 (0)131 272 7000 fax :: +44 (0)131 272 7001 email :: sales@wolfsonmicro.com

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