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WM8740 24-bit, high performance 192khz stereo dac advanced information, july 2000, rev 1.7 wolfson microelectronics ltd lutton court, bernard terrace, edinburgh, eh8 9nx, uk tel: +44 (0) 131 667 9386 fax: +44 (0) 131 667 5176 email: sales@wolfson.co.uk http://www.wolfson.co.uk advanced information data sheets contain preliminary data on new products in the preproduction phase of development. supplementary data will be published at a later date. ? 2000 wolfson microelectronics ltd . description the WM8740 is a very high performance stereo dac designed for audio applications such as cd, dvd, home theatre systems, set top boxes and digital tv. the WM8740 supports data input word lengths from 16 to 24-bits and sampling rates up to 192khz. the WM8740 consists of a serial interface port, digital interpolation filter, multi-bit sigma delta modulator and stereo dac in a small 28-pin ssop package. the WM8740 also includes a digitally controllable mute and attenuator function on each channel. the internal digital filter has two selectable roll-off characteristics. a sharp or slow roll-off can be selected dependent on application requirements. additionally, the internal digital filter can be by-passed and the WM8740 used with an external digital filter. the WM8740 supports two connection schemes for audio dac control. the spi-compatible serial control port provides access to a wide range of features including on- chip mute, attenuation and phase reversal. a hardware controllable interface is also available. features ? 120db snr (?a? weighted mono @48khz), thd+n: -104db @ fs ? 117db snr (?a? weighted stereo @48khz), thd+n: -104db @ fs ? sampling frequency: 8khz to 192khz ? selectable digital filter roll-off ? optional interface to industry standard external filters ? differential mono mode needing no glue logic ? input data word: 16 to 24-bit ? hardware or spi compatible serial port control modes: ? hardware mode: mute, de-emphasis, audio format control ? serial mode: mute, de-emphasis, attenuation (256 steps), phase reversal ? fully differential voltage outputs applications ? cd, dvd audio ? home theatre systems ? professional audio systems block diagram serial interface mute/ atten control interface bckin (3) (12) voutrp sigma delta modulator lrcin (1) din (2) agndr (10) avddr (9) mute/ atten sigma delta modulator digital filters mode8x (4) mux (8) dvdd (15) avdd (14) agnd (7) dgnd muteb (25) diffhw (6) md/dm0 (26) mc/dm1 (27) ml/i2s (28) mode (24) csbiwo (23) rstb (22) zero (21) low pass filter low pass filter (11) vmidr mux (18) vmidl right dac left dac (19) agndl (20) avddl . WM8740 sclk (5) (16) voutln (13) voutrn (17) voutlp
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 2 pin configuration ordering information device temp. range package xWM8740eds -25 to +85 c 28-pin ssop 16 15 14 20 19 18 17 5 6 7 1 2 3 4 13 12 11 8 9 10 bckin voutrn voutln lrcin din zero muteb mode rstb csbiwo md/dm0 mc/dm1 ml/i2s vmidr vmidl sclk diffhw mode8x agndr agndl avddr dvdd avddl dgnd 21 22 23 24 25 26 27 28 voutrp agnd voutlp avdd pin description pin name type description 1 lrcin digital input sample rate clock input. 2 din digital input audio data serial input (except in 8xmode when it is dinl). 3 bckin digital input audio data bit clock input . 4 mode8x digital input internal pull-down, active high, 8 x fs mode. 5 sclk digital input system clock input. 6 diffhw digital input internal pull-down, active high, differential mono mode. 7 dgnd supply digital ground supply. 8 dvdd supply digital positive supply. 9 avddr supply analogue positive supply. 10 agndr supply analogue ground supply. 11 vmidr analogue output mid rail right channel. 12 voutrp analogue output right channel dac output positive. 13 voutrn analogue output right channel dac output negative. 14 agnd supply analogue ground supply. 15 avdd supply analogue positive supply. 16 voutln analogue output left channel dac output negative. 17 voutlp analogue output left channel dac output positive. 18 vmidl analogue output mid rail left channel. 19 agndl supply analogue ground supply. 20 avddl supply analogue positive supply. 21 zero digital output infinite zero detect ? active low. open drain type output with active pull-down. 22 rstb digital input reset input ? active low. internal pull-up.
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 3 pin name type description hardware mode normal mode differential mode 8x mode software mode 23 csbiwo digital input internal pull-down wordlength: low for 16-bit data. high for 20-bit (normal) or 24-bit i 2 s data. wordlength: low for 16-bit data. high for 20-bit (normal) or 24-bit i 2 s data. wordlength: low for 20-bit data. high for 24-bit data. low for serial interface operation. 24 mode digital input internal pull-up low for hardware mode. low for left mono mode. high for right mono mode dinr high for software mode. 25 muteb digital input internal pull-up low to soft mute. high for normal operation. low to soft mute. high for normal operation. low to soft mute. high for normal operation. low to soft mute. high for normal operation. 26 md/dm0 digital input internal pull-up de-emphasis mode select bit 0. low for no de-emphasis. high for 44.1khz de-emphasis. lrp ? lrclk polarity select. control serial interface data signal. 27 mc/dm1 digital input internal pull-up de-emphasis mode select bit 1. low for normal filter operation. high for filter slow roll-off. unused. leave unconnected. control serial interface clock signal. 28 ml/i2s digital input internal pull-up audio serial format: low ? right justified. high ? i 2 s. audio serial format: low ? right justified. high ? i 2 s. input data format: low ? right justified. high ? left justified. control serial interface load signal. note: digital input pins have schmitt trigger input buffers. 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. condition min max supply voltage -0.3v +7.0v reference input vdd + 0.3v operating temperature range, t a -25 c+85 c storage temperature -65 c +150 c package body temperature (soldering, 10 seconds) +240 c package body temperature (soldering, 2 minutes) +183 c
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 4 recommended operating conditions parameter symbol test conditions min typ max unit digital supply range dvdd -10% 3.3 to 5 +10% v analogue supply range avdd -10% 3.3 to 5 +10% v ground agnd, dgnd 0 v difference dgnd to agnd -0.3 0 +0.3 v analogue supply current avdd = 5v 15 ma digital supply current dvdd = 5v 15 ma analogue supply current avdd = 3.3v 15 ma digital supply current dvdd = 3.3v 9 ma electrical characteristics test conditions avdd, dvdd = 5v, agnd, dgnd = 0v, t a = +25 o c, fs = 48khz, scki = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit dac circuit specifications mono fs @ 48khz 120 db stereo fs @ 48khz 110 117 db snr (see note 1) stereo fs @ 96khz 116 db mono 0db -104 db thd (full-scale) (see note 2) stereo 0db -95 -104 db thd+n (dynamic range) (see note 2) -60db 117 db filter characteristics (sharp roll-off) passband 0.0012 db 0.4535fs db stopband -3db 0.491fs passband ripple 0.0012 db stopband attenuation f > 0.5465fs -82 db delay time 30/fs s filter characteristics (slow roll-off) passband 0.001db 0.274fs stopband -3db 0.459fs passband ripple 0.001 db stopband attenuation f > 0.732fs -82 db delay time 9/fs s internal analogue filter bandwidth -3db 195 khz passband edge response 20khz -0.043 db digital logic levels input low level v il 0.8 input high level v ih 2.0 v output low level v ol i ol = 2ma avss + 0.3v v output high level v oh i oh = 2ma avdd - 0.3v
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 5 test conditions avdd, dvdd = 5v, agnd, dgnd = 0v, t a = +25 o c, fs = 48khz, scki = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit analogue output levels into 10kohm, full scale 0db, (5v supply) 2 v rms output level differential into 10kohm, full scale 0db, (3.3v supply) 1.32 v rms to midrail or ac coupled (5v supply) 1 kohms minimum resistance load to midrail or ac coupled (3.3v supply) 600 ohms maximum capacitance load 5v or 3.3v 100 pf output dc level avdd/2 v reference levels potential divider resistance avdd to vmidl/vmidr and vmidl/vmidr to agnd 10 kohms voltage at vmidl/vmidr avdd/2 por por threshold 2.2 v notes: 1. ratio of output level with 1khz full scale input, to the output level with all zeros into the digital input, measured ? a ? weighted over a 20hz to 20khz bandwidth. 2. all performance measurements done with 20khz low pass 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. bckin din lrcin t bch t bcl t bl t lb t bcy t ds t dh figure 1 audio data input timing test conditions avdd, dvdd = 5v, agnd, dgnd = 0v, t a = +25 o c, fs = 48khz, scki = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit audio data input timing information bckin pulse cycle time t bcy 100 ns bckin pulse width high t bch 40 ns bckin pulse width low t bcl 40 ns bckin rising edge to lrcin edge t bl 20 ns lrcin rising edge to bckin rising edge t lb 20 ns
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 6 test conditions avdd, dvdd = 5v, agnd, dgnd = 0v, t a = +25 o c, fs = 48khz, scki = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit din setup time t ds 20 ns din hold time t dh 20 ns scki t sckil t sckih t scky figure 2 system clock timing requirements test conditions avdd, dvdd = 5v, agnd, dgnd = 0v, t a = +25 o c, fs = 48khz, scki = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit system clock timing information system clock pulse width high t sckih 10 ns system clock pulse width low t sckil 10 ns system clock cycle time t scky 27 ns ml/i2s mc/dm1 md/dm0 t mhh t mld t mcy t mch t mcl t mds t mdh lsb t mls t mll figure 3 program register input timing ? spi compatible serial control mode test conditions avdd, dvdd = 5v, agnd, dgnd = 0v, t a = +25 o c, fs = 48khz, scki = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit program register input information mc/dm1 pulse cycle time t mcy 80 ns mc/dm1 pulse width low t mcl 32 ns md/dm0 pulse width high t mch 32 ns md/dm0 set-up time t mds 10 ns mc/dm1 hold time t mdh 10 ns ml/i2s pulse width low t mll 10 ns ml/i2s pulse width high t mhh 10 ns ml/i2s set-up time t mls 10 ns ml/i2s delay from mc t mld 10 ns
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 7 device description the WM8740 is a high performance 128fs oversampling rate stereo dac employing a novel 64 level sigma delta dac design which provides optimised signal-to-noise performance and clock jitter tolerance. it is ideally suited to high quality audio applications such as cd, dvd-audio, home theatre receivers and professional mixing consoles. the WM8740 supports sample rates from 8ks/s to 192ks/s. the control functions of the WM8740 are either pin selected (hardware mode) or programmed via the serial interface (software mode). control functions that are available include: data input word length and format selection (16-24 bits: i 2 s, left justified or right justified): de-emphasis sample rate selection (48khz, 44.1khz and 32khz); differential output modes; a software or hardware mute and independently digitally controllable attenuation on both channels. the digital filtering may be bypassed entirely by selecting mode8x. data is then input directly to the dac, bypassing the digital filters. left and right channels are input separately, using the mode pin as the right channel input. this mode allows the use of alternative digital filters, such as the pacific microsonics pmd100 hdcd filter. in addition to the normal stereo operating mode the WM8740 may also be used in dual differential mode with either the left or right channel (selectable) being output dual differentially. two WM8740s can then be used in parallel to implement a stereo channel, each supporting a single channel differentially. note that this mode uses 2 pairs of differential outputs for each channel ? the benefit is snr improved by 3db. this mode is available in both software and hardware modes and may also be used in conjunction with mode8x. system clock sample rates from 8ks/s up to 96ks/s are available, and automatically selected, with a system clock of 256fs or 384fs. in addition a system clock of 128fs or 192fs may be used, with sample rates up to 192ks/s. with a 128fs or 192fs system clock 64x oversampling mode operation is automatically selected and the first stage of the digital filter is bypassed. WM8740 has an asynchronous monitor circuit, which in the event of removal of the master system clock, resets the digital filters and analogue circuits, muting the output. re-application of the system clock re-starts the filters from an intitialised state. control registers are not reset under this condition. the WM8740 is tolerant of asynchronous bit clock jitter. the internal signal processing resynchronises to the external lrcin once the phase difference between bit clock and the system clock exceeds half an lrcin period. during this re-synch period the interpolating filters will either miss or repeat an audio sample, minimising the audible effects of the operation. table 1 shows the typical system clock frequency inputs for the WM8740. system clock frequency (mhz) sampling rate (lrcin) 128fs 192fs 256fs 384fs 32khz 4.096 6.144 8.192 12.288 44.1khz 5.6448 8.467 11.2896 16.9340 48khz 6.114 9.216 12.288 18.432 96khz 12.288 18.432 24.576 36.864 192khz 24.576 36.864 unavailable unavailable table 1 system clock frequencies versus sampling rate audio data interface data may be input at a rate corresponding to the system clock having a rate of 256fs or 384fs, in which case an oversampling ratio of 128x is selected. alternatively a rate of 128fs or 192fs may be used, in which case the first filter stage is bypassed and an oversampling ratio of 64x results. finally, in mode8x, data may be input at 8x the normal rate, in which case separate input pins are used to input the two stereo channels of data (unless diffhw mode and mode8x are both selected, in which case only a mono channel is converted differentially). in mode8x all filter stages are by- passed, prior to the sigma delta modulator. data is input msb first in all modes.
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 8 normal sample rate in normal mode, the data is input serially on one pin for both left and right channels. data can be ? right justified ? meaning that the last 16, 20 or 24 bits (depending on chosen pcm word length) that were clocked in prior to the transition on lrcin are valid. alternatively data can be ? left justified ? (20 and 24-bit pcm data only), where the bits are clocked in as the first 20 or 24 bits after a transition on lrcin. for the three i 2 s modes supported (16-bit, 20-bit and 24-bit pcm data), data is clocked ? left justified ? except with one additional preceding clock cycle. lrcin (pin 1) 16-bit right justified din (pin 2) 20-bit right justified din (pin 2) 24-bit right justified din (pin 2) 24-bit left justified din (pin 2) 20-bit left justified din (pin 2) bckin (pin 3) b2 b1 b0 b2 b1 b0 b2 b1 b0 b0 b0 b23 b22 b21 b19 b18 b17 b23 b22 b21 b20 b19 b4 b3 b2 b1 b0 b0 b19 b18 b17 b15 b2 b1 b0 b2 b1 b0 b2 b1 b0 b23 b22 b21 b19 b18 b17 b0 b4 b3 b2 b1 b0 b23 b22 b21 b20 b19 b19 b18 b17 b15 b2 b1 b0 b2 b1 b0 b2 b1 b0 right left 1/fs lrcin (pin 1) 16-bit i 2 s din (pin 2) 24-bit i 2 s din (pin 2) 20-bit i 2 s din (pin 2) bckin (pin 3) b2 b1 b0 b0 b2 b1 b0 b3 b2 b1 right left b15 b23 b19 b6 b5 b4 b2 b1 b0 b3 b2 b1 b15 b23 b19 b6 b5 b4 b0 b2 b1 b0 b23 b19 b15 figure 4 audio data input format
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 9 8 x fs input sample rate due to the higher speed of the interface in 8 x fs mode, audio data is input on two pins. the mode pin (pin 24) is used as the second input for the right channel data and left data is input on din (pin2). in this mode, software control of the device is not available. the data can be input in two formats, left or right justified, selectable by ml/i2s and two word lengths (20 or 24 bit), selectable by csbiwo. in both modes the data is always clocked in msb first. for left justified data the word start is marked by the falling edge of lrcin. the data is clocked in on the next 20/24 bckin rising edges. this format is compatible with devices such as the pmd100. for right justified the data is justified to the rising edge of lrcin and the data is clocked in on the preceding 20/24 bckin rising edges before the lrcin rising edge. this format is compatible with devices such as the df1704 or sm5842. in both modes the polarity of lrcin can be switched using md/dm0. differential hardware mode can be used in conjunction with 8fs mode by setting the diffhw pin high. in differential 8fs mode the data is input on din and output differentially. mode is unused and must be tied low. lrcin (pin 1) left audio data din (pin 2) right audio data mode (pin 24) bckin (pin 3) 1/8fs b19 b22 b23 b20 b21 b2 b1 b0 b23 b22 b21 b20 b19 b22 b23 b20 b21 b2 b1 b0 b23 b22 b21 b20 lrcin (pin 1) left audio data din (pin 2) right audio data mode (pin 24) bckin (pin 3) 1/8fs b19 b22 b23 b20 b21 b2 b1 b0 b19 b22 b23 b20 b21 b2 b1 b0 figure 5 audio data input format (8 x fs operation) modes of operation control of the various modes of operation is either by software control over the serial interface, or by hard-wired pin control. selection of software or hardware mode is via mode pin. the following functions may be controlled either via the serial control interface or by hard wiring of the appropriate pins. hardware control modes when the mode pin is held ? low ? the following hardware modes of operation are available. in hardware differential mode or 8x mode some of these modes/control words are altered or unavailable.
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 10 de-emphasis control mddm1 pin 27 mcdmo pin 26 de-emphasis ll off l h 48khz h l 44.1khz h h 32khz table 2 de-emphasis control audio input format ml/i2s pin 28 csbiwo pin 23 data format l l 16 bit normal right justified l h 20 bit normal right justified h l 16 bit i 2 s h h 24 bit i 2 s table 3 audio input format soft mute muteb pin 25 function l mute on (no output) h mute off (normal operation) table 4 soft mute a logic low on the muteb pin will cause the attenuation to ramp to infinite attenuation at a rate of 128/fs seconds per 0.5db step. setting muteb high will cause the attenuation to ramp back to its previous value. software control interface the WM8740 can be controlled using a 3-wire serial interface. md/dm0 (pin 26) is used for the program data, mc/dm1 (pin 22) is used to clock in the program data and ml/i2s (pin 28) is use to latch in the program data. the 3-wire interface protocol is shown in figure 6. csb/iwo (pin 23) must be low when writing. ml/i2s (pin 28) mc/dm1 (pin 27) md/dm0 (pin 26) b15 b14 b13 b2 b1 b0 figure 6 three-wire serial interface
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 11 register map WM8740 controls the special functions using 4 program registers, which are 16-bits long. these registers are all loaded through input pin md/dm0. after the 16 data bits are clocked in, ml/i2s is used to latch in the data to the appropriate register. table 5 shows the complete mapping of the 4 registers. note that in hardware differential mode and 8x modes, software control is not available. the hardware differential mode (diff[1:0]) clock loss detector disable ( cdd) can only be accessed by writing to m2[8:5] with the pattern 1111. register m4 is then accessible by setting a[2:0] to 110. b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 m0 ----a2 (0)a1(0)a0(0)ldlal7al6al5al4al3al2al1al0 m1 ----a2(0)a1(0)a0(1)ldrar7ar6ar5ar4ar3ar2ar1ar0 m2 ----a2(0)a1(1)a0(0)----iw1iw0opedemmut m3 ----a2(0)a1(1)a0(1)izdsf1sf0ck0revsr0atclrpi 2 s m4 ----a2(1)a1(1)a0(0)--cdddiff1diff0---- table 5 mapping of program registers register bits name default description [7:0] al[7:0] ff attenuation data for left channel. 0 8ldl 0 attenuation data load control for left channel. [7:0] ar[7:0] ff attenuation data for right channel. 1 8ldr 0 attenuation data load control for right channel. 0mut 0 left and right dacs soft mute control. 1dem 0 de-emphasis control. 2ope 0 left and right dacs operation control. 2 [4:3] iw[1:0] 0 input audio data bit select. 0i2s 0 audio data format select. 1lrp 0 polarity of lrcin select. 2atc 0 attenuator control. 3sr0 0 digital filter slow roll-off select. 4rev 0 output phase reverse. 5cko 0 clko frequency select. [7:6] sf[1:0] 0 sampling rate select. 3 8izd 0 infinite zero detection circuit control. [5:4] diff 0 differential output mode. 4 6 cdd 0 clock loss detector disable. table 6 register bit descriptions dac output attenuation the level of attenuation for eight bit code x, is given by: 0.5 ? (x - 255) db, 1 x 255 - db (mute), x = 0 bit 8 in register 0 (ldl) is used to control the loading of attenuation data in b[7:0]. when ldl is set to 0, attenuation data will be loaded into al[7:0], but it will not affect the filter attenuation. ldr in register 1 has the same function for right channel attenuation. only when ldl or ldr is set to ? 1 ? will the filter attenuation be updated. this permits left and right channel attenuation to be updated simultaneously. attenuation level is controlled by al[7:0] (left channel) or ar[7:0] (right channel). attenuation levels are given in table 7.
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 12 x[7:0] attenuation level 00(hex) - db (mute) 01(hex) -127.0db :: :: fd(hex) -1.0db fe(hex) -0.5db ff(hex) 0.0db table 7 attenuation control level bit 2 in reg3 is used to control the attenuator (atc). when atc is ? high ? , the attenuation data loaded in program register 0 is used for both the left and the right channels. when atc is low, the attenuation data for each register is applied separately to left and right channels. soft mute mut (reg2, b0) l soft mute off (normal operation) h soft mute on (no output) table 8 soft mute setting mut causes the attenuation to ramp from the current value down to 00. the values held in the attenuation registers are unchanged. when mut is reset the attenuation will ramp back up to the previous value. the ramp rate is 128/fs s/0.5db step. digital de-emphasis dem (reg2, b1) l de-emphasis off h de-emphasis on table 9 digital de-emphasis dac operation enable ope (reg2,b2) l normal operation h dac output forced to bipolar zero, irrespective of input data. table 10 dac operation enable audio data input format i2s (reg3, b0) iw1 (reg2, b4) iw0 (reg2, b3) audio interface 000 16-bit standard right justified 001 20-bit standard right justified 010 24-bit standard right justified 011 24-bit left justified (msb first) 100 16-bit i 2 s 101 24-bit i 2 s 110 20-bit i 2 s 111 20-bit left justified (msb first) table 11 audio data input format
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 13 polarity of lr input clock the left channel data for a particular sample instant is always input first, then the right channel data. lrp (reg3, b1) l lr high ? left channel lr low ? right channel h lr low ? left channel lr high ? right channel table 12 polarity of lr input clock individual or common attenutation control atc (reg3, b2) l individual control h common control from reg0 table 13 individual or common attenuation control digital filter roll-off selection sro (reg3, b3) l sharp h slow table 14 digital filter roll-off selection analogue output polarity reversal rev (reg3, b4) l normal h inverted table 15 analogue output polarity reversal clko output frequency cko (reg3, b5) l xti h xti/2 table 16 clko output frequency de-emphasis sample rate sf1 (reg3, b7) sf0 (reg3, b6) sample rate 0 0 no de-emphasis 0 1 48khz 1 0 44.1khz 1 1 32khz table 17 de-emphasis sample rate infinite zero detect izd (reg3, b8) l zero detect mute off h zero detect mute on table 18 infinite zero detect
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 14 differential mono mode using bits 4 and 5, the differential output mode may be selected to be one of normal stereo, reversed stereo, mono left or mono right, as shown in table 19. diff[1:0] b[4:5]) differential output mode 00 stereo 01 stereo reverse. 10 mono left ? differential outputs. voutl is left channel. voutr is the negative of left channel. 11 mono right ? differential outputs. voutl is the negative right channel. voutr is right channel. table 19 differential output modes using these controls a pair of WM8740 devices may be used to build a dual differential stereo implementation with higher performance and differential output. note: diffhw mode pin may be used to achieve the same result by hardware means. clock loss detector disable cdd (reg4, b6) l clock loss detector on r clock loss detector off table 20 clock loss detector disable when the system clock is inactive for approximately 100 s, the clock loss detector circuit detects the loss of clock and the analogue circuitry is forced into a mute condition and the digital filters reset. setting the cdd bit disables this behaviour. mute modes the device has various mute modes. analogue digital filter anres anmute reg bit ope = ? 1 ? unaffected asserted muteb pin gain ramped to zero on release volume ramps to previous value asserted when gain = 0 automute (detect 1024 zero input samples) automute has no effect on digital filters asserted after 1024 zero input samples if izd = 1 reg bit mut as muteb pin as muteb pin gain = 00 (left & right) gain = - db asserted ram initialise gain initialised to 0db asserted loss of system clock not running (no clock). on clock restart, filters initialised, ram initialised. registers unchanged asserted asserted no lrclk or invalid sclk/lrclk ratio filters initialised, ram initialised. registers unchanged asserted asserted rb reset ? gain initialised to 0db asserted asserted power-on reset reset asserted asserted table 21 mute modes
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 15 ? anres is the reset to the switched capacitor filter. ? anmute is an analogue muting signal gating the analogue signal at the output (after the sc filter) ? automute is asserted when both the izd register bit is asserted and the input audio data has been zero on both left and right channels for 1024 input samples. the first non-zero sample de-asserts. ? applying a logic low to muteb or setting mut in reg2 causes the gain registers to ramp to zero. when a logic high is applied, the gain ramps slowly back up to the value held in the appropriate attenuation register (al or ar). the ramp rate = 128/fs s/0.5db step. if softmute is set or muteb=0 then gainl and gainr are overridden to 00 muteb gainl[0:7] gainr[0:7] anmute softmute gain ramps between previous and new gain setting signal processing izd zero ope freq_invalid init automute: detect 1024 zero input samples figure 7 mute modes
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 16 filter responses figure 8 digital filter response (sharp roll-off mode) figure 9 digital filter response (sharp roll-off mode) figure 10 digital filter response (slow roll-off mode) figure 11 digital filter response (slow roll-off mode) -120 -100 -80 -60 -40 -20 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 response (db) frequency (fs) figure 12 digital filter response 128fs mode (192khz sample rate) normal mode ? solid, slow mode ? dashed
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 17 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 0 10 20 30 40 50 60 impulse response time (input samples) -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 0 10 20 30 40 50 60 impulse response time (input samples) figure 13 impulse response (normal roll-off, no de-emphasis) figure 14 impulse response (slow roll-off, no de-emphasis)
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 18 recommended external components 28 dvdd dgnd ml/i2s agnd avddl avdd 11 vmidr c 11 c 10 c 9 agnd 8 7 software i/f or hardware control WM8740 notes: 1. agnd and dgnd should be connected as close to the WM8740 as possible. 2. c 2 to c 5 , c 9 and c 11 should be positioned as close to the WM8740 as possible. 3. capacitor type used can have a big effect on device performance. it is recommended that capacitors with very low esr are used and that ceramics are either npo or cog type material to achieve best performance from the WM8740. avddr agndr agndl c 3 c 4 c 5 c 6 agnd c 2 dvdd c 1 27 mc/dm1 26 md/dm0 23 csb/iwo 22 rstb 12 mode8x 6 diffhw 21 zero avdd avdd r 1 18 vmidl c 12 1 lrcin 2 din 3 bckin 5 sclk audio serial data i/f system clock input dgnd + + + + 15 9 20 14 10 19 24 mode 25 muteb voutrn voutrp - - + + 13 12 left output data right output data voutlp 17 voutln 16 figure 15 external components diagram recommended external components values component reference suggested value description c1 and c6 10 f de-coupling for dvdd and avdd. c2 to c5 0.1 f de-coupling for dvdd and avdd. c7 and c8 10 f output ac coupling caps to remove vmid dc level from outputs. c9 and c11 0.1 f c10 and c12 10 f reference de-coupling capacitors for vmidr and vmidl. r1 10k ? resistor to avdd for open drain output operation. table 22 external components description
advanced information WM8740 wolfson microelectronics ltd ai rev 1.7 july 2000 19 suggested differential output filter circuit figure 16 suggested differential output filter circuit
WM8740 advanced information wolfson microelectronics ltd ai rev 1.7 july 2000 20 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 = ah. refer to this specification for further details. dm007.b ds: 28 pin ssop (10.2 x 5.3 x 1.75 mm) symbols dimensions (mm) min nom max a ----- ----- 2.13 a 1 0.05 ----- 0.25 a 2 1.62 1.75 1.88 b 0.22 ----- 0.38 c 0.09 ----- 0.20 d 9.90 10.20 10.50 e 0.65 bsc e 7.40 7.80 8.20 e 1 5.00 5.30 5.60 l 0.63 0.90 1.03 0 o 4 o 8 o ref: jedec.95, mo-150 a a2 a1 seating plane -c- 0.10 c 14 1 d 15 28 e1 e e b c l gauge plane 0.25

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