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[ak8975/c] ak8975/AK8975C 3-axis electronic compass 1. features 1. features a 3-axis electronic compass ic with high sensitive hall sensor technology. best adapted to pedestrian city navigation use for cell phone and other portable appliance. functions: ? 3-axis magnetometer device suitable for compass application ? built-in a to d converter for magnetometer data out ? 13 bit data out for each 3 axis magnetic components - sensitivity: 0.3 t / lsb typ. ? serial interface - i 2 c bus interface. standard mode and fast mode compliant with philips i 2 c specification ver.2.1 - 4-wire spi ? operation mode: power-down mode, single measurement mode, self test mode and fuse access mode. ? drdy function for measurement data ready ? magnetic sensor overflow monitor function ? built-in oscillator for internal clock source ? power on reset circuit ? self test function with built-in internal magnetic source operating temperatures: ? -30c to +85c operating supply voltage: ? analog power supply +2.4v to +3.6v ? digital interface supply +1.65v to analog power supply voltage. current consumption: ? power-down: 10 a max. ? measurement: - average power consumption at 8 hz repetition rate: 350 a typ. package: ak8975 16-pin qfn package: 4.0 mm 4.0 mm 0.75 mm AK8975C 14-pin wl-csp (bga): 2.0 mm 2.0 mm 0.6 mm ms1187-e-02 - 1 - 2010/05
[ak8975/c] 2. overview ak8975/c is 3-axis electronic compass ic with high sensitive hall sensor technology. small package of ak8975/c incorporates magnetic sensors for detecting terrestrial magnetism in the x-axis, y-axis, and z-axis, a sensor driving circuit, signal amplifier chain, and an arithmetic circuit for processing the signal from each sensor. self test function is also inco rporated. from its compact foot print and thin package feature, it is suitable for map heading up purpose in gps-equipped cell phone to realize pedestrian navigation function. ak8975/c has the following features: (1) silicon monolithic hall-effect magnetic sensor with magnetic concentrator realizes 3-axis magnetometer on a silicon chip. analog circuit, digital logic, power block and interface block are also integrated on a chip. (2) wide dynamic measurement range and high resolution with lower current consumption. output data resolution: 13 bit (0.3 t / lsb) measurement range: 1200 t average power consumption at 8hz repetition rate: 350 a typ. (3) digital serial interface - i 2 c bus interface to control ak8975/c functions and to read out the measured data by external cpu. a dedicated power supply for i 2 c bus interface can work in low-voltage apply as low as 1.65v. - 4-wire spi is also supported. a dedicated power supply for spi can work in low-voltage apply as low as 1.65v. (4) drdy pin and register inform to system that measurem ent is end and set of data in registers are ready to be read. (5) device is worked by on-chip oscillator so no external clock source is necessary. (6) self test function with internal magnetic source to confirm magnetic sensor operation on end products. ms1187-e-02 - 2 - 2010/05
[ak8975/c] 3. table of contents 1. features ....................................................................................................................................1 2. overview ...................................................................................................................................2 3. table of contents ......................................................................................................................3 4. circuit configuration ..................................................................................................................5 4.1. block diagram ....................................................................................................................5 4.2. block function ....................................................................................................................5 4.3. pin function .......................................................................................................................6 5. overall characteristics ..............................................................................................................7 5.1. absolute maximum ratings ................................................................................................7 5.2. recommended operating conditions ................................................................................7 5.3. electrical characteristics ....................................................................................................7 5.3.1. dc characteristics ......................................................................................................7 5.3.2. ac characteristics ......................................................................................................8 5.3.3. analog circuit characteristics .....................................................................................8 5.3.4. 4-wire spi ...................................................................................................................9 5.3.5. i 2 c bus interface .......................................................................................................10 6. functional explanation ............................................................................................................ 11 6.1. power states .................................................................................................................... 11 6.2. reset functions ............................................................................................................... 11 6.3. operation modes ..............................................................................................................12 6.4. description of each operation mode ................................................................................13 6.4.1. power-down mode ....................................................................................................13 6.4.2. single measurement mode .......................................................................................13 6.4.2.1. data ready ........................................................................................................13 6.4.2.2. data error ..........................................................................................................14 6.4.2.3. magnetic sensor overflow .................................................................................14 6.4.3. self-test mode ...........................................................................................................15 6.4.4. fuse rom access mode ..........................................................................................15 7. serial interface ........................................................................................................................16 7.1. 4-wire spi .........................................................................................................................16 7.1.1. writing data ..............................................................................................................16 7.1.2. reading data ............................................................................................................17 7.2. i 2 c bus interface ..............................................................................................................18 7.2.1. data transfer ............................................................................................................18 7.2.1.1. change of data ..................................................................................................18 7.2.1.2. start/stop condition ...........................................................................................18 7.2.1.3. acknowledge ......................................................................................................19 7.2.1.4. slave address ....................................................................................................19 7.2.2. write instruction .....................................................................................................20 7.2.3. read instruction .......................................................................................................21 7.2.3.1. one byte read .................................................................................................21 7.2.3.2. multiple byte read ...........................................................................................21 8. registers ............................................................................................................................... ..22 8.1. description of registers ...................................................................................................22 8.2. register map ....................................................................................................................23 8.3. detailed description of registers .....................................................................................24 8.3.1. wia: device id ..........................................................................................................24 8.3.2. info: information ......................................................................................................24 8.3.3. st1: status 1 .............................................................................................................24 8.3.4. hxl to hzh: measurement data ...............................................................................25 8.3.5. st2: status 2 .............................................................................................................26 8.3.6. cntl: control ...........................................................................................................26 8.3.7. rsv: reserved .........................................................................................................27 8.3.8. astc: self test control ............................................................................................27 8.3.9. ts1, ts2: test 1, 2 ...................................................................................................27 8.3.10. i2cdis: i 2 c disable ...................................................................................................27 8.3.11. asax, asay, asaz: sensitivity adjustment values ...................................................28 ms1187-e-02 - 3 - 2010/05
[ak8975/c] 9. example of recommended external connection ....................................................................29 9.1. i 2 c bus interface ..............................................................................................................29 9.2. 4-wire spi .........................................................................................................................30 10. package ............................................................................................................................... ...31 10.1. marking ............................................................................................................................31 10.2. pin assignment ................................................................................................................31 10.3. outline dimensions ..........................................................................................................32 10.4. recommended foot print pattern ....................................................................................33 11. relationship between the magnet ic field and output code ....................................................34 ms1187-e-02 - 4 - 2010/05
[ak8975/c] 4. circuit configuration 4.1. block diagram 3-axis hall sensor mux sda/si drdy chopper sw he-drive pre- amp integrator adc interface, logic & register scl/sk vd d voltage reference timin g control vid so osc1 csb magnetic source cad0 vss por fuse rom cad1 ts t1 tst2 rsv ts t6 4.2. block function block function 3-axis hall sensor monolithic hall elements. mux multiplexer for sele cting hall elements. chopper sw performs chopping. he-drive magnetic sensor drive circuit for co nstant-current driving of sensor pre-amp variable-gain differential amplifier used to amplify the magnetic sensor signal. integrator & adc integrates and amplifies pre-amp output and performs analog-to-digital conversion. osc1 generates an operating clock for sensor measurement. 6.144mhz(typ.) por power on reset circuit. generates reset signal on rising edge of vdd. interface logic exchanges data with an external cpu. drdy pin indicates sensor measurement end and data is ready to be read. i 2 c bus interface using two pins, namely, scl and sda. standard mode and fast mode are supported. the low-voltage specification can be supported by applying 1.65v to the vid pin. 4-wire spi is also supported by sk, si, so and csb pins. 4-wire spi works in vid pin voltage down to 1.65v, too. timing control generates a timing signal required for internal operation from a clock generated by the osc1. magnetic source generates magnetic field for self test of magnetic sensor. fuse rom fuse for adjustment ms1187-e-02 - 5 - 2010/05
[ak8975/c] 4.3. pin function pin no. 75 75c pin name i/o power supply system type function 1 a1 tst1 o vdd analog test pin. hi-z output. keep this pin electrically nonconnected. 2 a2 csb i vid cmos chip select pin for 4-wire spi. ?l? active. connect to vid when selecting i 2 c bus interface. 3 a4 rsv i vid cmos reserved pin. keep this pin electrically nonconnected or connect to vss. scl when the i 2 c bus interface is selected (csb pin is connected to vid) scl: control data clock input pin input: schmidt trigger 4 a3 sk i vid cmos when the 4-wire spi is selected sk: serial clock input pin sda i/o when the i 2 c bus interface is selected (csb pin is connected to vid) sda: control data input/output pin input: schmidt trigger, output: open drain 5 d4 si i vid cmos when the 4-wire spi is selected si: serial data input pin when the i 2 c bus interface is selected (csb pin is connected to vid) hi-z output. keep this pin electrically nonconnected. 6 b4 so o vid cmos when the 4-wire spi is selected serial data output pin 7 c4 vid - - power digital interface positive power supply pin. 8 - nc1 non-contact pin. keep this pin electrically nonconnected. 9 b3 tst6 o vid cmos test pin. vss output. keep this pin electric ally nonconnected or connect to vss.. 10 c3 drdy o vid cmos data ready signal output pin. active ?h?. informs measurement ended and data is ready to be read. when the i 2 c bus interface is selected (csb pin is connected to vid) cad1: slave address 1 input pin connect to vss or vdd. 11 d2 cad1 i vdd cmos when the 4-wire serial interface is selected connect to vss. 12 - nc2 non-contact pin. keep this pin electrically nonconnected. when the i 2 c bus interface is selected (csb pin is connected to vid) cad0: slave address 0 input pin connect to vss or vdd. 13 d1 cad0 i vdd cmos when the 4-wire serial interface is selected connect to vss. 14 c2 tst2 o vdd analog test pin. hi-z output. keep this pin electrically nonconnected. 15 c1 vss - - power ground pin. 16 b1 vdd - - power analog power supply pin. ms1187-e-02 - 6 - 2010/05
[ak8975/c] 5. overall characteristics 5.1. absolute maximum ratings vss=0v parameter symbol min. max. unit power supply voltage (vdd, vid) v+ -0.3 +6.5 v input voltage vin -0.3 (v+)+0.3 v input current iin - 10 ma storage temperature tst -40 +125 c (note 1) if the device is used in conditions exceeding these values, the device may be destroyed. normal operations are not guaranteed in such exceeding conditions. 5.2. recommended operating conditions vss=0v parameter remark symbol min. typ. max. unit operating temperature ta -30 +85 c vdd pin voltage vdd 2.4 3.0 3.6 v power supply voltage vid pin voltage vid 1.65 vdd v 5.3. electrical characteristics the following conditions apply unless otherwise noted: vdd=2.4v to 3.6v, vid=1.65v to vdd, temperature range=-30 c to 85 c 5.3.1. dc characteristics parameter symbol pin condition min. typ. max. unit high level input voltage 1 vih1 70%vid v low level input voltage 1 vil1 csb sk si 30%vid v high level input voltage 2 vih2 70%vid v low level input voltage 2 vil2 scl sda 30%vid v high level input voltage 3 vih3 70%vdd v low level input voltage 3 vil3 cad0 cad1 30%vdd v input current iin scl sk sda si csb vin=vss or vid -10 +10 a vid 2v 5%vid v hysteresis input voltage (note 2) vhs scl sda vid<2v 10%vid v high level output voltage 1 voh1 ioh -100a (note 5) 80%vid v low level output voltage 1 vol1 so drdy iol +100a (note 5) 20%vid v iol 3ma vid 2v 0.4 v low level output voltage 2 (note 3) (note 4) vol2 sda iol 3ma vid<2v 20%vid v idd1 power-down mode vdd=vid=3.0v 3 10 a idd2 when magnetic sensor is driven 6 10 ma current consumption idd3 (note 6) vdd vid self-test mode 10.3 15 ma (note 2) schmitt trigger input (reference value for design) (note 3) maximum load capacitance: 400pf (capacitive load of each bus line applied to the i 2 c bus interface) (note 4) output is open-drain. connect a pull-up resistor externally. (note 5) load capacitance: 20pf (note 6) reference value for design. ms1187-e-02 - 7 - 2010/05
[ak8975/c] 5.3.2. ac characteristics parameter symbol pin condition min. typ. max. unit power supply rise time (note 7) tpup vdd period of time from 10%vdd to 90%vdd (note 8) 200 s power-down mode transit time (note 7) vdd period of time from 90%vdd at power-on to power-down mode 100 s wait time before mode setting twat 100 s (note 7) reference value for design (note 8) only when vdd meets this condition, por circuit starts and resets ak8975/c. after reset, all registers are initialized and ak8975/c transits to power-down mode. tpup 10%vdd 90%vdd 5.3.3. analog circ uit characteristics parameter symbol condition min. typ. max. unit measurement data output bit dbit 13 bit time for measurement tsm single measurement mode 7.3 9 ms magnetic sensor sensitivity bse tc=25 c (note 9) 0.285 0.3 0.315 t/lsb magnetic sensor measurement range (note 10) brg tc=25c (note 9) 1229 t magnetic sensor initial offset (note 11) tc=25c -1000 +1000 lsb (note 9) value after sensitivity is adjusted us ing sensitivity fine adjustment data stored in fuse rom. (refer to 8.3.11 for how to adjust.) (note 10) reference value for design (note 11) value of measurement data register on shipment without applying magnetic field on purpose. ms1187-e-02 - 8 - 2010/05
[ak8975/c] 5.3.4. 4-wire spi 4-wire spi is compliant with mode 3 parameter symbol condition min. typ. max. unit csb setup time tcs 50 ns data setup time ts 50 ns data hold time th 50 ns vid 2.5v 100 ns sk high time twh 2.5v>vid 1.65v 150 ns vid 2.5v 100 ns sk low time twl 2.5v>vid 1.65v 150 ns sk setup time tsd 50 ns sk to so delay time (note 12) tdd 50 ns csb to so delay time (note 12) tcd 50 ns sk rise time (note 13) tr 100 ns sk fall time (note 13) tf 100 ns csb high time tch 150 ns (note 12) so load capacitance: 20pf (note 13) reference value for design. [4-wire spi] csb sk si tc s so ts tsd tcd th tdd hi-z hi-z twh twl tch [rise time and fall time] sk t r tf 0.9vid 0.1vid ms1187-e-02 - 9 - 2010/05
[ak8975/c] 5.3.5. i 2 c bus interface csb pin = ?h? i 2 c bus interface is compliant with standard mode and fast mode. standard/fast mode is selected automatically by fscl. (1) standard mode fscl 100khz 1.65v vid vdd symbol parameter min. typ. max. unit fscl scl clock frequency 100 khz thigh scl clock "high" time 4.0 s tlow scl clock "low" time 4.7 s tr sda and scl rise time 1.0 s tf sda and scl fall time 0.3 s thd:sta start condition hold time 4.0 s tsu:sta start condition setup time 4.7 s thd:dat sda hold time (vs. scl falling edge) 0 s tsu:dat sda setup time (vs. scl rising edge) 250 ns tsu:sto stop condition setup time 4.0 s tbuf bus free time 4.7 s (2) fast mode 100khz [ak8975/c] 6. functional explanation 6.1. power states when vdd and vid are turned on from vdd=off (0v) and vid=off (0v), all registers in ak8975/c are initialized by por circuit and ak8975/c transits to power-down mode. all the states in the table below can be set, although th e transition from state 2 to state 3 and the transition from state 3 to state 2 are prohibited. states vdd vid power states 1 off (0v) off (0v) off (0v). scl, sda should be fixed to the voltage that does not exceed 3.6v. other digital pins should be fixed to l(0v). 2 off (0v) 1.65v to 3.6v off (0v). it doesn?t affect external interface. 3 2.4v to 3.6v off (0v) off (0v). it consumes current same as power-down mode. scl, sda should be fixed to the voltage that does not exceed 3.6v. other digital pins should be fixed to l (0v). 4 2.4v to 3.6v 1.65v to vdd on table 6.1 6.2. reset functions ak8975/c has two types of reset; (1) power on reset (por) when vdd reaches approximately 2v (reference value for design), por circuit operates, and ak8975/c is reset. (2) vid monitor when vid is turned off (0v), ak8975/c is reset. when ak8975/c is reset, all registers are initialized and ak8975/c transits to power-down mode. ms1187-e-02 - 11 - 2010/05
[ak8975/c] 6.3. operation modes ak8975/c has following four operation modes: (1) power-down mode (2) single measurement mode (3) self-test mode (4) fuse rom access mode by setting cntl register mode[3:0] bits, the operation set for each mode is started. a transition from one mode to another is shown below. mode[3:0]=?0001? tra nsits au to ma tically mode[3:0]=?0000? mode[3:0]=?1000? tra nsits au to ma tically mode[3:0]=?0000? m o de [3 :0]= ?11 11 ? m o de [3 :0]= ?00 00 ? power-down mode self-test mode se nso r is self -te st ed an d th e resu lt is o ut pu t. tran sits to power-down mode automatically. single measurement mode se nso r is me asur ed for on e time a nd d ata is ou tp ut. transits to power-down mode automatically after measurement ended. fuse rom access mode turn o n th e circu it ne ed ed to re ad o ut fu se r om. transits to power-down mode by writing mode[3:0]=?0000?. figure 6.1 operation modes when power is turned on, ak8975/c is in power-down mode. when mode[3:0] is set, ak8975/c transits to the specified mode and starts operat ion. when user wants to change operation mode, transit to power-down mode first and then transit to other modes. after power-down mode is set, at least 100 p s(twat) is needed before setting another mode. ms1187-e-02 - 12 - 2010/05
[ak8975/c] 6.4. description of e ach operation mode 6.4.1. power-down mode power to all internal circuits is turned off. all regi sters except fuse rom are accessible in power-down mode. data stored in read/write registers are remained. 6.4.2. single measurement mode when single measurement mode (mode[3:0]=?0001?) is set, sensor is measured, and after sensor measurement and signal processing is finished, measur ement data is stored to measurement data registers (hxl to hzh), then ak8975/c transits to power-dow n mode automatically. on transition to power-down mode, mode[3:0] turns to ?0000?. at the same time, drdy bit in st1 register turns to ?1?. this is called ?data ready?. when any of measurement data register (hxl to hzh) or st2 register is read, or operation mode is changed from power-down mode to other mode, drdy bit turns to ?0?. drdy pin is in the same state as drdy bit. operation mode: single measuremnet power-down (1) (2) (3) measurement period measurement data register last data indefinit e measurement data (1) indefinit e data(2) indefinit e data(3) drdy register read data register data register register write mode[3:0]="0001" mode[3:0]="0001" mode[3:0]="0001" figure 6.2 single measurement mode 6.4.2.1. data ready when measurement data is stored and ready to be read, drdy bit in st1 register turns to ?1?. this is called ?data ready?. drdy pin is in the same state as dr dy bit. when measurement is performed correctly, ak8975/c becomes data ready on transition to power-down mode (pd) after measurement. the period from the end of nth measurement to the start of (n+1)th m easurement is called ?data readable period?. stored measurement data should be read during data readable period. (n-1)th nth (n+1)th measurement measurement pd pd pd data readable period data readable period figure 6.3 data readable period ms1187-e-02 - 13 - 2010/05
[ak8975/c] 6.4.2.2. data error when data reading is started out of data readable period, read data is not correct. in this case, derr bit of st2 register turns to ?1? so that read data can be checked at the end of data reading. derr turns to ?0? when st2 register is read. (n-1)th nth (n+1)th pd measurement pd measurement pd data readable period data readable period measurement data register (n-1)th indefinite nth indefinite (n+1)th in d drdy derr register read st1 data st2 st1 data st2 st1 data st2 register register register figure 6.4 data error 6.4.2.3. magnetic sensor overflow ak8975/c has the limitation for measurement range that the sum of absolute values of each axis should be smaller than 2400 t. |x|+|y|+|z| < 2400 t when the magnetic field exceeded this limitation, data stored at measurement data are not correct. this is called magnetic sensor overflow. when magnetic sensor overlow occurs, hofl bit turns to ?1?. when the next measurement starts, it returns to ?0?. ms1187-e-02 - 14 - 2010/05
[ak8975/c] 6.4.3. self-test mode self-test mode is used to check if the sensor is working normally. when self-test mode (mode[3:0]=?1000?) is set, magnetic field is generated by the internal magnetic source and sensor is measured. measurement data is stored to measurement data registers (hxl to hzh), then ak8975/c transits to power-down mode automatically. before setting self-test mode, write ?1? to self bit of astc register. data read sequence and functions of read-only registers in self-test mode is the same as single measurement mode. when self-test is end, write ?0? to self bit then proceed to other operation. (1) set power-down mode (2) write ?1? to self bit of astc register (3) set self-test mode (4) check data ready or not by any of the following method. - polling drdy bit of st1 register - monitor drdy pin when data ready, proceed to the next step. (5) read measurement data (hxl to hzh) (6) write ?0? to self bit of astc register when measurement data read by th e above sequence is in the range of following table after sensitivity adjustment (refer to 8.3.11 ), ak8975/c is working normally. hx[15:0] hy[15:0] hz[15:0] criteria -100 x +100 -100 y +100 -1000 z -300 6.4.4. fuse rom access mode fuse rom access mode is used to read fuse rom data.sensitivity adjustment data for each axis is stored in fuse rom. these data are used in calcul ation of direction by the external cpu. when fuse rom mode (mode[3:0]=?1111?) is set, circ uits reauired fo r reading fuse rom are turned on. after reading fuse rom data, set power-down mode (mode[3:0]=?0000?). ms1187-e-02 - 15 - 2010/05
[ak8975/c] 7. serial interface ak8975/c supports i 2 c bus interface and 4-wire spi. a selection is made by csb pin. when used as 3-wire spi, set si pin and so pin wired-or externally. csb pin=?l?: 4-wire spi csb pin=?h?: i 2 c bus interface 7.1. 4-wire spi the 4-wire spi consists of four digital signal lines: sk, si, so, and csb. it is compliant with sequencial read operation. data consists of read/write control bit (r/w), register address (7bits) and control data (8bits). csb pin is low active. input data is taken in on the rising edge of sk pin, and output data is changed on the falling edge of sk pin. (spi mode3) communication starts when csb pin transits to ?l? and stops when csb pin transits to ?h?. sk pin must be ?h? during csb pin is in transition. also, it is prohibited to change si pin during csb pin is ?h? and sk pin is ?h?. 7.1.1. writing data input 16 bits data on si pin in synchronous with the 16-bit serial clock input on sk pin. out of 16 bits input data, the first 8 bits specify the r/w control bit (r/w=?0? when writing) and register address (7bits), and the latter 8 bits are control data (8bits ). when any of addresses listed on table 8.1 is input, ak8975/c recognizes that it is selected and takes in latter 8 bits as setting data. if the number of clock pulses is less than 16, no data is written. if the number of clock pulses is more than 16, data after the 16th clock pulse on si pin are ignored. it is not compliant with sereal write operation for multiple addresses. csb sk si (input) 1 rw so (output) hi-z a6 a5 a4 a3 a2 a1 a0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 d7 d6 d5 d4 d3 d2 d1 d0 figure 7.1 4-wire spi writing data ms1187-e-02 - 16 - 2010/05
[ak8975/c] 7.1.2. reading data input the r/w control bit (r/w=?1?) and 7 bit register address on si pin in synchronous with the first 8 bits of the 16 bits of a serial clock input on sk pin. then ak8975/c outputs the data held in the specified register with msb first from so pin. when clocks are input continuously after one byte of da ta is read, the address is incremented and data in the next address is output. accordingly, after the falling edge of the 15th clock and csb pin is ?l?, the data in the next address is output on so pin. when csb pin is driven ?l? to ?h?, so pin is placed in the high-impedance state. ak8975/c has two incrementation lines; 00h to 0ch and 10h to 12h. for example, data is read as follows: 00h -> 01h ... -> 0bh -> 0ch -> 00h -> 01h ..., and 10h -> 11h -> 12h -> 10h ? when specified address is other than 00h to 12h, ak8975/c recognizes that it is not selected and keeps so pin in high-impedance state. therefore, user can use other addresses for other devices. csb sk si (input) 1 rw so (output) hi-z a6 a 5 a 4 a 3 a2 a 1 a 0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 d7 d6 d5 d4 d3 d2 d1 d0 hi-z figure 7.2 4-wire spi reading data ms1187-e-02 - 17 - 2010/05
[ak8975/c] 7.2. i 2 c bus interface the i 2 c bus interface of ak8975/c supports the standard mode (100 khz max.) and the fast mode (400 khz max.). 7.2.1. data transfer to access ak8975/c on the bus, generate a start condition first. next, transmit a one-byte slave address including a device address. at this time, ak8975/c compares the slave address with its own address. if these addresses match, ak8975/c generates an acknowledgement, and then executes read or write instruction. at the end of instruction execution, generate a stop condition. 7.2.1.1. change of data a change of data on the sda line must be made during "low" period of the clock on the scl line. when the clock signal on the scl line is "high", the state of th e sda line must be stable. (data on the sda line can be changed only when the clock signal on the scl line is "low".) during the scl line is "high", the state of data on the sda line is changed only when a start condition or a stop condition is generated. scl sda data line stable : data valid change of data a llowed figure 7.3 data change 7.2.1.2. start/stop condition if the sda line is driven to "low" from "high" when the scl line is "high", a start condition is generated. any instruction starts with a start condition. if the sda line is driven to "high" from "low" when the scl line is "high", a stop condition is generated. any instruction stops with a stop condition. scl sda stop condition start condition figure 7.4 start and stop conditions ms1187-e-02 - 18 - 2010/05
[ak8975/c] 7.2.1.3. acknowledge the ic that is transmitting data releases the sda lin e (in the "high" state) after sending 1-byte data. the ic that receives the data drives the sda line to "low" on the next clock pulse. this operation is referred to acknowledge. with this operation, whether data ha s been transferred successfully can be checked. ak8975/c generates an acknowledge after reception of a start cond ition and slave address. when a write instruction is executed, ak8975/c generates an acknowledge after every byte is received. when a read instruction is executed, ak8975/ c generates an acknowledge then transfers the data stored at the specified address. next, ak8975/c releases the sda line then monitors the sda line. if a master ic generates an acknowledge instead of a stop condition, ak8975/c transmits the 8bit data stored at the next address. if no acknowledge is generated, ak8975/c stops data transmission. scl from master acknowledge data output by transmitter data output by receiver 1 9 8 start condition clock pulse for acknowledge not acknowledge figure 7.5 generation of acknowledge 7.2.1.4. slave address the slave address of ak8975/c can be selected from the following list by setting cad0/1 pin. when cad pin is fixed to vss, the corresponding slave address bit is ?0?. when cad pin is fixed to vdd, the corresponding slave address bit is ?1?. cad1 cad0 slave address 0 0 0ch 0 1 0dh 1 0 0eh 1 1 0fh table 7.1 slave address and cad0/1 pin the first byte including a slave address is transmitted after a start condition, and an ic to be accessed is selected from the ics on the bus according to the slave address. when a slave address is transferred, the ic whose device address matches the transferred slave address generates an acknowledge then executes an instruction. the 8th bit (least significant bit) of the first byte is a r/w bit. when the r/w bit is set to "1", read instruction is executed. when the r/w bit is set to "0", write instruction is executed. msb lsb 0 0 0 1 1 cad1 cad0 r/w figure 7.6 slave address ms1187-e-02 - 19 - 2010/05
[ak8975/c] 7.2.2. write instruction when the r/w bit is set to "0", ak8975/c performs write operation. in write operation, ak8975/c generates an acknowledge after receiving a start condition and the first byte (slave address) then receives the second byte. the second byte is used to specify the address of an internal control register and is based on the msb-first configuration. msb lsb a7 a6 a5 a4 a3 a2 a1 a0 figure 7.7 register address after receiving the second byte (register address), ak8975/c generates an acknowledge then receives the third byte. the third and the following bytes represent control data. control data consists of 8 bits and is based on the msb-first configuration. ak8975/c generates an acknow ledge after every byte is received. data transfer always stops with a stop condition generated by the master. msb lsb d7 d6 d5 d4 d3 d2 d1 d0 figure 7.8 control data ak8975/c can write multiple bytes of data at a time. after reception of the third byte (c ontrol data), ak8975/c generates an acknowledge then r eceives the next data. if additional data is received instead of a stop condition after receiving one byte of data, the address counter inside the lsi chip is automatically incremented and the data is written at the next address. the address is incremented from 00h to 0ch or from 10h to12h. when the address is in the range from 00h to 0ch, the address goes back to 00h after 0ch. when the address is in the range from 10h to 12h, the address goes back to 10h after 12h. actual data is written only to read/write registers (0ah to 0fh). sda s t a r t a c k a c k s slave a ddress a c k register a ddress(n) data(n) p s t o p data(n+x) a c k data(n+1) a c k a c k r/w= " 0 " figure 7.9 write instruction ms1187-e-02 - 20 - 2010/05
[ak8975/c] 7.2.3. read instruction when the r/w bit is set to "1", ak8975/c performs read operation. if a master ic generates an acknowledge instead of a stop condition after ak8975/c transfers the data at a specified address, the data at the next address can be read. address can be from 00h to 0ch and/or from 10h to 12h.when address is counted up to 0ch in the range of 00h to 0ch, the next address returns to 00h. when address is counted up to 12h in the range of 10h to 12h, the next address returns to 10h. ak8975/c supports one byte read and multiple byte read. 7.2.3.1. one byte read ak8975/c has an address counter inside the lsi chip. in current address read operation, the data at an address specified by this counter is read. the internal address counter holds the next ad dress of the most recently accessed address. for example, if the address most recently accessed (for re ad instruction) is address "n", and a current address read operation is attempted, the data at address "n+1" is read. in one byte read operation, ak8975/c generates an acknowledge after receiving a slave address for the read instruction (r/w bit="1"). next, ak8975/c transfers the data specified by the internal address counter starting with the next clock pulse, then increments the intern al counter by one. if the master ic generates a stop condition instead of an acknowledge after ak8975/c transmits one byte of data, the read operation stops. sda s t a r t a c k a c k s slave address a c k data(n) data(n+1) p s t o p data(n+x) a c k data(n+2) a c k r/w= " 1 " figure 7.10 one byte read 7.2.3.2. multiple byte read by multiple byte read operation, data at an arbitrary address can be read. the multiple byte read operation requires to execute write instruction as dummy before a slave address for the read instruction (r/w bit="1") is transmitted. in random read operation, a start condition is first generated then a slave address for the write instruction (r/w bit="0") and a read address are transmitted sequentially. after ak8975/c generates an acknowledge in response to this address transmission, a start condition and a slave address for the read instruction (r/w bit="1") are generated again. ak8975/c generates an acknowledge in response to th is slave address transmission. next, ak897 5/c transfers the data at the specified address then increments the internal address counter by one. if the master ic generates a stop condition instead of an acknowledge after data is transferred, the read operation stops. sda s t a r t a c k a c k s slave address a c k registe r address(n) data(n) p s t o p data(n+x) a c k data(n+1) a c k r/w= " 0 " s t a r t a c k s slave address r/w= " 1 " figure 7.11 multiple byte read ms1187-e-02 - 21 - 2010/05
[ak8975/c] 8. registers 8.1. description of registers ak8975/c has registers of 19 addresses as indicated in table 8.1 . every address consists of 8 bits data. data is transferred to or received from the external cp u via the serial interface described previously. name address read/ write description bit width explanation wia 00h read device id 8 info 01h read information 8 st1 02h read status 1 8 data status hxl 03h 8 hxh 04h 8 x-axis data hyl 05h 8 hyh 06h 8 y-axis data hzl 07h 8 hzh 08h read measurement data 8 z-axis data st2 09h read status 2 8 data status cntl 0ah read/ write control 8 rsv 0bh read/ write reserved 8 do not access astc 0ch read/ write self-test 8 ts1 0dh read/ write test 1 8 do not access ts2 0eh read/ write test 2 8 do not access i2cdis 0fh read/ write i 2 c disable 8 asax 10h read x-axis sensitivity adjustment value 8 fuse rom asay 11h read y-axis sensitivity adjustment value 8 fuse rom asaz 12h read z-axis sensitivity adjustment value 8 fuse rom table 8.1 register table addresses from 00h to 0ch and from 10h to 12h are compliant with automatic increment function of serial interface respectively. values of addresses from 10h to 12h can be read only in fuse access mode. in other modes, read data is not correct. ms1187-e-02 - 22 - 2010/05
[ak8975/c] 8.2. register map addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 00h wia 0 1 0 0 1 0 0 0 01h info info7 info6 info5 info4 info3 info2 info1 info0 02h st1 0 0 0 0 0 0 0 drdy 03h hxl hx7 hx6 hx5 hx4 hx3 hx2 hx1 hx0 04h hxh hx15 hx14 hx13 hx12 hx11 hx10 hx9 hx8 05h hyl hy7 hy6 hy5 hy4 hy3 hy2 hy1 hy0 06h hyh hy15 hy14 hy13 hy12 hy11 hy10 hy9 hy8 07h hzl hz7 hz6 hz5 hz4 hz3 hz2 hz1 hz0 08h hzh hz15 hz14 hz13 hz12 hz11 hz10 hz9 hz8 09h st2 0 0 0 0 hofl derr 0 0 write/read register 0ah cntl 0 0 0 0 mode3 mode2 mode1 mode0 0bh rsv - - - - - - - - 0ch astc - self - - - - - - 0dh ts1 - - - - - - - - 0eh ts2 - - - - - - - - 0fh i2cdis - - - - - - - i2cdis read-only register 10h asax coefx7 coefx6 coefx5 coefx4 coefx3 coefx2 coefx1 coefx0 11h asay coefy7 coefy6 coefy5 coefy4 coefy3 coefy2 coefy1 coefy0 12h asaz coefz7 coefz6 coefz5 co efz4 coefz3 coefz2 coefz1 coefz0 table 8.2 register map when vdd is turned on, por function works and all registers of ak8975/c are initialized regardless of vid status. to write data to or to re ad data from register, vid must be on. ts1 and ts2 are test registers for shipme nt test. do not use these registers. rsv is reserved register. do not use this register. ms1187-e-02 - 23 - 2010/05
[ak8975/c] 8.3. detailed description of registers 8.3.1. wia: device id addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 00h wia 0 1 0 0 1 0 0 0 device id of akm. it is described in one byte and fixed value. 48h: fixed 8.3.2. info: information addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 01h info info7 info6 info5 info4 info3 info2 info1 info0 info[7:0]: device information for akm. 8.3.3. st1: status 1 addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 02h st1 0 0 0 0 0 0 0 drdy reset 0 0 0 0 0 0 0 0 drdy: data ready "0": normal "1": data is ready drdy bit turns to ?1? when data is ready in single measurement mode or self-test mode. it returns to ?0? when any one of st2 register or measuremen t data register (hxl to hzh) is read. ms1187-e-02 - 24 - 2010/05
[ak8975/c] 8.3.4. hxl to hzh: measurement data addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 03h hxl hx7 hx6 hx5 hx4 hx3 hx2 hx1 hx0 04h hxh hx15 hx14 hx13 hx12 hx11 hx10 hx9 hx8 05h hyl hy7 hy6 hy5 hy4 hy3 hy2 hy1 hy0 06h hyh hy15 hy14 hy13 hy12 hy11 hy10 hy9 hy8 07h hzl hz7 hz6 hz5 hz4 hz3 hz2 hz1 hz0 08h hzh hz15 hz14 hz13 hz12 hz11 hz10 hz9 hz8 reset 0 0 0 0 0 0 0 0 measurement data of magnetic sensor x-axis/y-axis/z-axis hxl[7:0]: x-axis measurement data lower 8bit hxh[15:8]: x-axis measurement data higher 8bit hyl[7:0]: y-axis measurement data lower 8bit hyh[15:8]: y-axis measurement data higher 8bit hzl[7:0]: z-axis measurement data lower 8bit hzh[15:8]: z-axis measurement data higher 8bit measuremnet data is stored in two?s complement and little endian format. measurement range of each axis is from -4096 to +4095 in decimal. measurement data (each axis) [15:0] two?s complement hex decimal magnetic flux density [t] 0000 1111 1111 1111 0fff 4095 1229(max.) | | | | 0000 0000 0000 0001 0001 1 0.3 0000 0000 0000 0000 0000 0 0 1111 1111 1111 1111 ffff -1 -0.3 | | | | 1111 0000 0000 0000 f000 -4096 -1229(min.) table 8.3 measurement data format ms1187-e-02 - 25 - 2010/05
[ak8975/c] 8.3.5. st2: status 2 addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 09h st2 0 0 0 0 hofl derr 0 0 reset 0 0 0 0 0 0 0 0 derr: data error "0": normal "1": data read error occurred when data reading is started out of data readable period, the read data are not correct. in this case, data read error occurs an d derr bit turns to l 1 z . when st2 register is read, it returns to l 0 z . hofl: magnetic sensor overflow "0": normal "1": magnetic sensor overflow occurred in single measurement mode and self-test mode, magnetic sensor may overflow even though measurement data regiseter is not saturated. in this case, measurement data is not correct and hofl bit turns to ?1?. when next measurement stars, it returns to ?0?. refer to 6.4.2.3 for detailed information. 8.3.6. cntl: control addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 0ah cntl 0 0 0 0 mode3 mode2 mode1 mode0 reset 0 0 0 0 0 0 0 0 mode[3:0]: operation mode setting "0000": power-down mode "0001": single measurement mode "1000": self-test mode "1111": fuse rom access mode other code settings are prohibited when each mode is set, ak8975/c transits to set mode. refer to 6.3 for detailed information. when cntl register is accessed to be written, registers from 02h to 09h are initialized. ms1187-e-02 - 26 - 2010/05
[ak8975/c] 8.3.7. rsv: reserved addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 0bh rsv - - - - - - - - reset 0 0 0 0 0 0 0 0 rsv register is reserved. do not use this register. 8.3.8. astc: self test control addr register name d7 d6 d5 d4 d3 d2 d1 d0 write/read register 0ch astc - self - - - - - - reset 0 0 0 0 0 0 0 0 self: self test control "0": normal "1": generate magnetic field for self-test do not write ?1? to any bit other than self bit in astc register. if ?1? is written to any bit other than self bit, normal measurement can not be done. 8.3.9. ts1, ts2: test 1, 2 addr register name d7 d6 d5 d4 d3 d2 d1 d0 write/read register 0dh ts1 - - - - - - - - 0eh ts2 - - - - - - - - reset 0 0 0 0 0 0 0 0 ts1 and ts2 registers are test registers for shipment test. do not use these registers. 8.3.10. i2cdis: i 2 c disable addr register name d7 d6 d5 d4 d3 d2 d1 d0 write/read register 0fh i2cdis - - - - - - - i2cdis reset 0 0 0 0 0 0 0 0 this register disables i 2 c bus interface. i 2 c bus interface is enabled in default. to disable i 2 c bus interface, write ?00011011? to i2cdis register. then i2cdis bit turns to ?1? and i 2 c bus interface is disabled. once i2cdis is turned to ?1? and i 2 c bus interface is disabled, re-setting i2cdist to ?0? is prohibited. to enable i 2 c bus interface, reset ak8975/c by tu rning vdd or vid to off (0v) once. ms1187-e-02 - 27 - 2010/05
[ak8975/c] 8.3.11. asax, asay, asaz: sensitivity adjustment values addr register name d7 d6 d5 d4 d3 d2 d1 d0 read-only register 10h asax coefx7 coefx6 coefx5 coefx4 coefx3 coefx2 coefx1 coefx0 11h asay coefy7 coefy6 coefy5 coefy4 coefy3 coefy2 coefy1 coefy0 12h asaz coefz7 coefz6 coefz5 co efz4 coefz3 coefz2 coefz1 coefz0 reset - - - - - - - - sensitivity adjustment data for each axis is stored to fuse rom on shipment. asax[7:0]: magnetic sensor x-axis sensitivity adjustment value asay[7:0]: magnetic sensor y-axis sensitivity adjustment value asaz[7:0]: magnetic sensor z-axis sensitivity adjustment value the sensitivity adjustment is done by the equation below; () ? ? ? ? ? ? + ? = 1 128 5.0128 asa hhadj , where h is the measurement data read out from the measurement data register, asa is the sensitivity adjustment value, and hadj is the adjusted measurement data. ms1187-e-02 - 28 - 2010/05
[ak8975/c] 9. example of recommended external connection 9.1. i 2 c bus interface <AK8975C> same as ak8975 tst1 drdy tst6 nc1 sda /si so cad0 vid 8 7 6 16 15 14 13 open open open open interrupt host cpu i 2 c i/f power for i/f vid power 1.65v~vdd vdd power 2.4v~3.6v 0.1f 0.1f 1 2 3 4 5 csb rsv scl / sk cad1 nc2 tst2 vss vdd 12 11 10 9 open slave address select cad1 cad0 address vss vss 0 0 0 1 1 0 0 r/w vss vdd 0 0 0 1 1 0 1 r/w vdd vss 0 0 0 1 1 1 0 r/w vdd vdd 0 0 0 1 1 1 1 r/w open ak8975 (top view) open or vss ms1187-e-02 - 29 - 2010/05
[ak8975/c] 9.2. 4-wire spi <AK8975C> same as ak8975 tst1 drdy tst6 nc1 sda/ si so cad0 vid 8 7 6 16 15 14 13 open open open interru p t host cpu 4-wirespi i/f power for i/f vid power 1.65v~vdd vdd power 2.4v~3.6v 0.1f 0.1f 1 2 3 4 5 csb rsv scl / sk cad1 nc2 tst2 vss vdd 12 11 10 9 ak8975 (top view) open open open or vss ms1187-e-02 - 30 - 2010/05
[ak8975/c] 10. package 10.1. marking ? company logo: akm ? product name: 8975 ? date code: x 1 x 2 x 3 x 4 x 5 x 1 = id x 2 = year code x 3 x 4 = week code x 5 = lot <AK8975C> ? product name: 8975c ? date code: x 1 x 2 x 3 x 4 x 5 x 1 = id x 2 = year code x 3 x 4 = week code x 5 = lot 8975c akm x 1 x 2 x 3 x 4 x 5 8975 x 1 x 2 x 3 x 4 x 5 10.2. pin assignment 14 so akm 8975 xxxxx 15 vid 16 nc1 8 7 scl/sk 4 rsv 3 tst6 9 drdy 10 nc2 11 cad1 12 csb 2 6 tst2 tst1 5 cad0 13 sda/si vss vdd 1 <AK8975C> 8975c xxxxx sd a /si cad1 tst1 cad0 csb tst6 so drdy tst2 scl /sk rsv vid vss vdd d c b a 4 3 2 1 ms1187-e-02 - 31 - 2010/05
[ak8975/c] 10.3. outline dimensions [mm] <AK8975C> [mm] 4.00 0.10 akm 8975 xxxxx 1 4 8 5 12 9 13 16 4.00 0.10 a b 0.75 0.05 2.6 4 3 2 1 1.96 d c b a 1.96 8975c xxxxx 0.075 c 0.65 max. c 0.40 0.19 0.5 1.5 1.5 0.5 0.27 0.03 d c b a 1 2 3 4 0.08 c 0.65 ref. 0.30 0.05 2.6 0.10 4 1 0.10 0.30 ref. 0.40 0.10 8 5 13 16 9 12 c0.30 . 0.10 m c a b 16x ms1187-e-02 - 32 - 2010/05
[ak8975/c] 10.4. recommended foot print pattern [mm] <AK8975C> [mm] 0.5 0.5 0.25 d c b a 4 3 2 1 ms1187-e-02 - 33 - 2010/05
[ak8975/c] 11. relationship between the magn etic field and output code the measurement data increases as the magnetic flux density increases in the arrow directions. <AK8975C> a k m 8 9 7 5 x x x x x y z x a k m 8 9 7 5 x x x x x a k m 8 9 7 5 x x x x x y z x y z x 8 9 7 5 c x x x x x y z x 8 9 7 5 c x x x x x 8 9 7 5 c x x x x x y z x important notice ? these products and their specifications are subject to change without notice. when you consider any use or application of these products, please make inquiries the sales office of asahi kasei microdevices corporation (akm) or aut horized distributors as to current status of the products. ? akm assumes no liability for infringement of any patent, intellectual property, or other rights in the application or use of any information contained herein. ? any export of these products, or devices or systems containing them, may require an export license or other official approval under the law and regulations of the country of export pertaining to customs and tariffs, currency exchange, or strategic materials. ? akm products are neither intended nor auth orized for use as critical components note1) in any safety, life support, or other hazard related device or system note2) , and akm assumes no responsibility for such use, except for the use approved with the express writte n consent by representative director of akm. as used here: note1) a critical component is one whose failure to function or perform may reasonably be expected to result, whether directly or indirectly, in the loss of the safety or effectiveness of the device or system containing it, and which must therefore meet very high standards of performance and reliability. note2) a hazard related device or system is one designed or intended for life support or maintenance of safety or for applications in medicine, aerospace, nuclear energy, or other fields, in which its failure to function or perform may reasonably be expected to re sult in loss of life or in significant injury or damage to person or property. ? it is the responsibility of the buyer or distributor of akm products, who distributes, disposes of, or otherwise places the product with a third party, to notify such third party in advance of the above content and conditions, and the buyer or distributor agrees to assume any and all responsibility and liability for and hold akm harmless from any and all claims arisi ng from the use of said product in the absence of such notification ms1187-e-02 - 34 - 2010/05

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