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w wm8521 stereo dac with integrated output stage for 2vrms line out wolfson microelectronics plc www.wolfsonmicro.com product preview, december 2004, rev 1.3 copyright ? 2004 wolfson microelectronics plc . description the wm8521 is a 96khz stereo dac with an integrated output op-amp stage, designed to generate a 2.0vrms output signal directly, so reducing external component requirements in digital audio applications. wm8521 comes into two variants wm8521hc and wm8521h9 which offers different line drive output capabilities. wm8521hc outputs 2vrms at 12v supply, while wm8521h9 outputs 2.0vrms at 9v supply. wm8521hc/h9 are designed for cost sensitive consumer digital audio applications requiring 2vrms line output. a 24-bit multi-bit sigma delta dac is used with oversampling digital interpolation filters. digital audio input word lengths from 16-32 bits and sampling rates from 8khz to 96khz are supported. the audio interface supports i 2 s, right justified and dsp digital audio formats. the devices are controlled via a hardware interface which provides access to features including de-emphasis, mute and data formats. these devices are pin equivalent and are available in a 14-pin soic package. features ? audio performance - dac snr 98db (?a? weighted @ 48khz) - thd -81db (?a? weighted @ 48khz) ? dac sampling frequency: 8khz ? 96khz ? pin selectable audio data interface format - i 2 s, 16-bit right justified or 16bit dsp ? 2.0 vrms output at 12v or 9v supply ? 8.2v to 13.2v analogue, 2.7v to 3.6 digital supply ? 14-pin soic package applications ? consumer digital audio applications requiring 2 vrms output - dvd players - digital tv - digital set top boxes - a/v receivers block diagram
wm8521 product preview w pp rev 1.3 december 2004 2 table of contents description .......................................................................................................1 features.............................................................................................................1 applications .....................................................................................................1 block diagram .................................................................................................1 pin configuration...........................................................................................3 ordering information ..................................................................................3 absolute maximum ratings.........................................................................5 dc electrical characteristics ................................................................6 electrical characteristics ......................................................................6 terminology............................................................................................................. 7 master clock timing.............................................................................................. 8 digital audio interface........................................................................................ 8 device description .........................................................................................9 general introduction.......................................................................................... 9 dac circuit description....................................................................................... 9 clocking schemes ................................................................................................ 10 digital audio interface...................................................................................... 10 audio data sampling rates ............................................................................... 12 hardware control modes................................................................................ 13 digital filter characteristics ....................................................................... 15 dac filter responses ......................................................................................... 15 digital de-emphasis characteristics ........................................................... 16 applications information .........................................................................17 recommended external components........................................................... 17 recommended external components values............................................ 17 recommended analogue low pass filter ................................................... 18 pcb layout recommendations......................................................................... 18 package drawing..........................................................................................19 important notice ..........................................................................................20 address:................................................................................................................... 20
product preview wm8521 w pp rev 1.3 december 2004 3 pin configuration ordering information device temperature range package moisture sensitivity level peak soldering temperature wm8521hced/v -25 to +85 o c 14-pin soic msl1 240 o c wm8521hced/rv -25 to +85 o c 14-pin soic (tape and reel) msl1 240 o c wm8521hcged/v -25 to +85 o c 14-pin soic (lead free) msl1 260 o c wm8521hcged/rv -25 to +85 o c 14-pin soic (lead free, tape and reel) msl1 260 o c wm8521h9ed/v -25 to +85 o c 14-pin soic msl1 240 o c wm8521h9ed/rv -25 to +85 o c 14-pin soic (tape and reel) msl1 240 o c wm8521h9ged/v -25 to +85 o c 14-pin soic (lead free) msl1 260 o c wm8521h9ged/rv -25 to +85 o c 14-pin soic (lead free, tape and reel) msl1 260 o c note: 1. reel quantity = 3,000 2. wm8521h9: 2vrms output at 9v supply 3. wm8521hc: 2vrms output at 12v supply
wm8521 product preview w pp rev 1.3 december 2004 4 pin description pin name type description 1 dgnd supply digital negative supply 2 lrclk digital input sample rate clock input 3 din digital input serial audio data input 4 bclk digital input bit clock input 5 mute digital input soft mute control, internal pull down high impedance = automute high = mute on low = mute off 6 voutr analogue output right channel dac output 7 agnd supply analogue negative supply 8 cap analogue output analogue internal reference 9 avdd supply analogue positive supply 10 voutl analogue output left channel dac output 11 deemph digital input de-emphasis select, internal pull down high = de-emphasis on low = de-emphasis off 12 format digital input data input format select, internal pull up low = 16-bit right justified or 16bit dsp ?late? high = 16-32-bit i 2 s or 16bit dsp ?early? 13 mclk digital input master clock input 14 dvdd supply digital positive supply note: 1. digital input pins have schmitt trigger input buffers.
product preview wm8521 w pp rev 1.3 december 2004 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 analogue supply voltage (avdd) -0.3v +15v digital supply voltage (dvdd) -0.3v +4.2v voltage range digital inputs dgnd -0.3v dvdd +0.3v master clock frequency 50mhz operating temperature range, t a -25 c +85 c storage temperature prior to soldering 30 c max / 85% rh max storage temperature after soldering -65 c +150 c
wm8521 product preview w pp rev 1.3 december 2004 6 dc electrical characteristics parameter symbol test conditions min typ max unit wm8521hc analogue supply range avdd 8.2 12 13.2 v wm8521h9 analogue supply range avdd 8.2 9 13.2 v digital supply range dvdd 2.7 3.3 3.6 v ground agnd / dgnd 0 v wm8521hc supply current avdd = 12v dvdd = 3.3v 32.0 ma wm8521h9 supply current avdd = 9v dvdd = 3.3v 24.9 ma wm8521hc power down current (note 4) avdd = 12v dvdd = 3.3v 23.7 ma wm8521h9 power down current (note 4) avdd = 9v dvdd = 3.3v 17.9 ma electrical characteristics test conditions wm8521hc : avdd = 12v, dvdd = 3.3v, agnd / dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. wm8521h9 : avdd = 9v, dvdd = 3.3v, agnd / 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 (cmos levels) input low level v il 0.7 x dvdd v input high level v ih 0.3 x dvdd v output low v ol i ol = 1ma 0.1 x dvdd v output high v oh i oh = -1ma 0.9 x dvdd v analogue reference levels reference voltage (cap) avdd/2 v potential divider resistance r cap vdd to cap and cap to gnd 50 k ? dac output (load = 10k ? ? ? ? . 50pf) wm8521hc 0dbfs full scale output voltage at dac outputs 2.0 v rms wm8521h9 0dbfs full scale output voltage at dac outputs 2.0 2.64 @ 12v avdd v rms snr (terminology note 1,2,3) a-weighted, @ fs = 48khz 95 98 db snr (terminology note 1,2,3) a-weighted @ fs = 96khz 98 db snr (terminology note 1,2,3) non ?a? weighted @ fs = 48khz 95 db thd (note 3) 1khz, 0dbfs -81 db dynamic range (note 2) 1khz, thd+n @ -60dbfs 91 98 db dac channel separation 1khz, 0dbfs 93 db
product preview wm8521 w pp rev 1.3 december 2004 7 test conditions wm8521hc : avdd = 12v, dvdd = 3.3v, agnd / dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. wm8521h9 : avdd = 9v, dvdd = 3.3v, agnd / 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 gain mismatch channel-to-channel 1 %fsr minimum resistance load to midrail or a.c. coupled 5 k ? maximum capacitance load 220 pf output d.c. level avdd/2 v power on reset (por) por threshold dvdd 1.64 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, 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. cap pin decoupled with 10uf and 0.1uf capacitors (smaller values may result in reduced performance). 4. digital reset occurs 1.5 s after mclk is stopped. 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 no 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.
wm8521 product preview w pp rev 1.3 december 2004 8 master clock timing mclk t mclkl t mclkh t mclky figure 1 master clock timing requirements test conditions avdd = 12v, dvdd = 3.3v, agnd / dgnd = 0v, t a = +25 o c, fs = 48khz, mclk = 256fs unless otherwise stated. parameter symbol test conditions min typ max unit system clock timing information mclk master clock pulse width high t mclkh 11 ns mclk master clock pulse width low t mclkl 11 ns mclk master clock cycle time t mclky 28 ns mclk duty cycle 40:60 60:40 time from mclk stopping to digital reset 1.5 12 s digital audio interface figure 2 digital audio data timing test conditions avdd = 12v, dvdd = 3.3v, agnd / 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 bclk cycle time t bcy 50 ns bclk pulse width high t bch 20 ns bclk pulse width low t bcl 20 ns lrclk set-up time to bclk rising edge t lrsu 10 ns lrclk hold time from bclk rising edge t lrh 10 ns din set-up time to bclk rising edge t ds 10 ns din hold time from bclk rising edge t dh 10 ns bclk lrclk t bch t bcl t bcy din t lrsu t ds t lrh t dh
product preview wm8521 w pp rev 1.3 december 2004 9 device description general introduction the wm8521 is a high performance dac designed for digital consumer audio applications requiring a 2vrms output. the range of features make it ideally suited for use in dvd players, digital tv, digital set top boxes, av receivers and other consumer audio equipment. the wm8521 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 combined with 2vrms outputs. it is fully compatible and an ideal partner for a range of industry standard microprocessors, controllers and dsps. a novel multi bit sigma-delta dac design is used, utilising a 128x oversampling rate, to optimise signal to noise performance and offer increased clock jitter tolerance. control of internal functionality of the device is provided by hardware control (pin programmed). operation using master clocks of 256fs, 384fs, 512fs or 768fs is provided, selection between clock rates being automatically controlled. sample rates (fs) from 8khz to 96khz are allowed provided the appropriate system clock is input. the audio data interface supports 16-bit right justified or 16-, 20-, 24-, 32-bit i 2 s (philips left justified, one bit delayed) interface formats. a 16bit dsp interface is also supported, enhancing the interface options for the user. the device is packaged in a small 14-pin soic. dac circuit description the wm8521 dac is designed to allow playback of 24-bit pcm audio or similar data with high resolution and low noise and distortion. sample rates from 8khz to 96khz may be used provided that the ratio of sample rate (lrclk) to master clock (mclk) is maintained at one of the required rates. the two dacs on the wm8521 are implemented using sigma-delta oversampled conversion techniques. these require that the pcm samples are digitally filtered and interpolated to generate a set of samples at a much higher rate than the input rate. this sample stream is then digitally modulated to generate a digital pulse stream that is then converted to analogue signals in a switched capacitor dac. the advantage of this technique is that the dac is linearised using noise shaping techniques, allowing the 24-bit resolution to be met using non-critical analogue components. a further advantage is that the high sample rate at the dac output means that smoothing filters on the output of the dac need only have fairly crude characteristics in order to remove the characteristic steps, or images on the output of the dac. to ensure that generation of tones characteristic to sigma-delta convertors is not a problem, dithering is used in the digital modulator along with a higher order modulator. the multi-bit switched capacitor technique used in the dac reduces sensitivity to clock jitter, and dramatically reduces out of band noise compared to switched current or single bit techniques used in other implementations. the voltage on the cap pin is used as the reference for the dacs. therefore the amplitude of the signals at the dac outputs will scale with the amplitude of the voltage at the cap pin. an external reference could be used to drive into the cap pin if desired, with a value typically of about midrail ideal for optimum performance. however driven in normal operation, an internal divider will set a valve of avdd/2 on the cap pin.
wm8521 product preview w pp rev 1.3 december 2004 10 typically an external low pass filter circuit will be used to remove residual out of band noise characteristic of delta sigma converters. however, the advanced multi-bit dac used in wm8521 produces far less out of band noise than single bit traditional sigma delta dacs, and so in many applications this filter may be removed, or replaced with a simple rc pole. 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 clock can be applied directly through the mclk input pin with no configuration necessary for sample rate selection. note that on the wm8521, mclk is used to derive clocks for the dac path. the dac path is affected by 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. the device can be reset by stopping mclk. in this state the power consumption is substantially reduced. digital audio interface audio data is applied to the internal dac filters via the digital audio interface. three interface formats are supported: ? i 2 s mode ? right justified mode ? dsp mode all formats send the msb first. the data format is selected with the format pin. when format is low, right justified data format is selected and word lengths up to 16-bits may be used. if a word length shorter than 16-bits is used, the unused bits should be padded with zeroes. when the format pin is high, i 2 s format is selected and word length of any value up to 32-bits may be used. unless in 16-bit ?packed? mode, if a word length shorter than 24-bits is used, the unused bits should be padded with zeros. if lrclk is 4 bclks or less duration, the 16bit dsp compatible format is selected. early and late clock formats are supported, selected by the state of the format pin. i 2 s mode input format the wm8521 supports word lengths of 16-32 bits in i 2 s mode. in i 2 s mode, the digital audio interface receives data on the din input. audio data is time multiplexed with lrclk indicating whether the left or right channel is present. lrclk is also used as a timing reference to indicate the beginning or end of the data words. 25-32 bits: lrclk must be high for a minimum of data wordlength bclks and low for a minimum of data wordlength bclks. the lsbs will be truncated and the most significant 24 bits will be used by the internal processing. 24 bits: lrclk must be high for a minimum of 24 bclks and low for a minimum of 24 bclks. 17-23 bits: data must be zero padded to 24 bits and lrclk must be high for a minimum of 24 bclks and low for a minimum of 24 bclks. up to 16 bits: either data must be zero padded to 24 bits and lrclk must be high for minimum 24 bclks and low for 24 bclks, or data must be zero padded to 16 bits and lrclk must be high for exactly 16 bclks and low for exactly 16 bclks. the device auto-detects this ?16-bit packed? mode and switches to 16-bit data length. any mark to space ratio on lrclk is acceptable provided the above requirements are met.
product preview wm8521 w pp rev 1.3 december 2004 11 in i 2 s mode, the msb is sampled on the second rising edge of bclk following a lrclk transition. lrclk is low during the left samples and high during the right samples. msb right channel left channel lrclk bclk din 3 3 12 3 12 n n-2 n-1 n n-2 n-1 1 bclk 1 bclk lsb msb lsb 1/fs figure 3 i 2 s mode timing diagram right justified mode input format the wm8521 supports word lengths of up to 16-bits in right justified mode. if a word length shorter than 16-bits is used, the unused bits should be padded with zeroes. in right justified mode, lrclk must be high for a minimum of 16 bclks and low for a minimum of 16 bclks. any mark to space ratio on lrclk is acceptable provided the above requirement is met. the digital audio interface receives data on the din input. audio data is time multiplexed with lrclk indicating whether the left or right channel is present. lrclk is also used as a timing reference to indicate the beginning or end of the data words. in right justified mode, the lsb is sampled on the rising edge of bclk preceding a lrclk transition. lrclk is high during the left samples and low during the right samples. right channel left channel lrclk bclk din 1/fs msb 3 3 12 14 15 16 lsb msb 3 3 12 14 15 16 lsb figure 4 right justified mode timing diagram dsp mode input format a dsp compatible, time division multiplexed format is also supported by the wm8521. this format is of the type where a ?synch? pulse is followed by two data words (left and right) of 16 bit word length. the ?synch? pulse replaces the normal duration lrclk, and dsp mode is auto-detected by the shorter than normal duration of the lrclk. if lrclk is of 4 bclk or less duration, the dsp compatible format is selected. early and late clock formats are supported, selected by the state of the format pin.
wm8521 product preview w pp rev 1.3 december 2004 12 right channel left channel lrclk bclk din 1/fs msb 12 15 16 lsb 12 15 16 msb 1 max 4 bclks no valid data input word length (16 bits) figure 5 dsp late mode timing right channel left channel lrclk bclk din 1/fs msb 12 15 16 lsb 12 15 16 max 4 bclks no valid data input word length (16 bits) 1 bclk 1 bclk figure 6 dsp early mode timing audio data sampling rates the master clock for wm8521 supports audio sampling rates from 256fs to 768fs, where fs is the audio sampling frequency (lrclk) typically 32khz, 44.1khz, 48khz or 96khz. the master clock is used to operate the digital filters and the noise shaping circuits. the wm8521 has a master clock detection circuit that automatically determines the relationship between the master clock frequency and the sampling rate (to within +/- 32 master clocks). if there is a greater than 32 clocks error, the master clock defaults to 768fs. the master clock should be synchronised with lrclk, although the wm8521 is tolerant of phase differences or jitter on this clock. master clock frequency (mhz) (mclk) sampling rate (lrclk) 256fs 384fs 512fs 768fs 32khz 8.192 12.288 16.384 24.576 44.1khz 11.2896 16.9344 22.5792 33.8688 48khz 12.288 18.432 24.576 36.864 96khz 24.576 36.864 unavailable unavailable table 1 master clock frequencies versus sampling rate note: for sample rates down to 8k, scale mclk accordingly.
product preview wm8521 w pp rev 1.3 december 2004 13 hardware control modes the wm8521 is hardware programmable providing the user with options to select input audio data format, de-emphasis and mute. mute and auto mute operation pin 5 (mute) controls the mute function, or can be used as an output to monitor the state of the automuted signal. mute pin description 0 normal operation, mute off 1 mute dac channels floating enable izd, mute becomes an output to indicate when izd occurs. table 2 mute and automute control figure 7 application and release of mute mute is active high; taking the pin high causes the filters to soft mute, ramping down the audio signal over a few milliseconds. taking mute low again allows data into the filter. refer to figure 7. therefore if mute is tied low then mute is disabled and the automute function is overridden. if mute is floating or connected to a high impedance then the automute function will operate. the automuted internal signal, which is generated by the izd function, is connected to the mute pin internally via a 10k resistor. this can provide a weak output (10k source impedance) which can be used to drive external mute circuits. refer to figure 8. the infinite zero detect (izd) function detects 1024 zero value audio samples applied to both channels. after such an event, a latch is set whose output is the automuted internal signal. automuted will be reset as soon as either channel receives a non-zero input. -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)
wm8521 product preview w pp rev 1.3 december 2004 14 a diagram showing how the various mute modes interact is shown below in figure 8. automuted (internal signal) 10k ? ? ? ? softmute (internal signal) mute pin figure 8 selection logic for mute modes input audio format selection format (pin 12) controls the data input format. format input data mode 0 16 bit right justified 1 16?32 bit i 2 s table 3 input audio format selection input dsp format selection format lrclk datawidth bclks lrclk of 4 bclk or less duration 0 16 bit (msb-first, right justified) 16 bit dsp format ? ?late? mode 1 i 2 s format up to 24 bit (philips serial data protocol) 16 bit dsp format ? ?early? mode table 4 dsp interface formats de-emphasis control deemph (pin 11) is an input control for selection of de-emphasis filtering to be applied. deemph de-emphasis 0 off 1 on table 5 de-emphasis control
product preview wm8521 w pp rev 1.3 december 2004 15 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 6 digital filter characteristics dac filter responses -120 -100 -80 -60 -40 -20 0 0 0.5 1 1.5 2 2.5 3 frequency (fs) response (db) figure 9 dac digital filter frequency response C 44.1,48 and 96khz -80 -70 -60 -50 -40 -30 -20 -10 0 10 0.4 0.45 0.5 0.55 0.6 frequency (fs) response (db) figure 10 dac digital filter transition band C 44.1,48 and 96khz -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0 0.1 0.2 0.3 0.4 0.5 frequency (fs) response (db) figure 11 dac digital filter ripple C 44.1, 48 and 96khz
wm8521 product preview w pp rev 1.3 december 2004 16 digital de-emphasis characteristics -10 -8 -6 -4 -2 0 0 2 4 6 8 10 12 14 16 response (db) frequency (khz) figure 12 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 13 de-emphasis error (32khz) -10 -8 -6 -4 -2 0 0 5 10 15 20 response (db) frequency (khz) figure 14 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 15 de-emphasis error (44.1khz) -10 -8 -6 -4 -2 0 0 5 10 15 20 response (db) frequency (khz) figure 16 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 17 de-emphasis error (48khz)
product preview wm8521 w pp rev 1.3 december 2004 17 applications information recommended external components figure 18 recommended external components recommended external components values component reference suggested value description c1 10 f de-coupling for avdd c2 0.1 f de-coupling for avdd c3 10 f de-coupling for dvdd c4 0.1 f de-coupling for dvdd c5 and c6 10 f output ac coupling caps to remove midrail dc level from outputs c7 0.1 f c8 10 f reference de-coupling capacitors for cap pin table 7 external components description
wm8521 product preview w pp rev 1.3 december 2004 18 recommended analogue low pass filter voutr voutl 220 ? 10nf 10k ? ac coupling cap 220 ? 10nf 10k ? ac coupling cap figure 19 recommended 1st order low pass filter an external single pole rc filter is recommended (see figure 19) if the device is driving a wideband amplifier. however the wm8521 does contain an internal low pass filter which should be adequate in most applications. pcb layout recommendations care should be taken in the layout of the pcb that the wm8521 is to be mounted to. the following notes will help in this respect: the vdd supply to the device should be as noise free as possible. this can be accomplished to a large degree with a 10uf bulk capacitor placed locally to the device and a 0.1uf high frequency decoupling capacitor placed as close to the vdd pin as possible. it is best to place the 0.1uf capacitor directly between the vdd and gnd pins of the device on the same layer to minimize track inductance and thus improve device decoupling effectiveness. the cap pin should be as noise free as possible. this pin provides the decoupling for the on chip reference circuits and thus any noise present on this pin will be directly coupled to the device outputs. in a similar manner to the vdd decoupling described in 1. above, this pin should be decoupled with a 10uf bulk capacitor local to the device and a 0.1uf capacitor as close to the cap pin as possible. separate analogue and digital track routing from each other . the device is split into analogue (pins 5 ? 10) and digital (pins 1 ? 4 & pins 11 ? 14) sections that allow the routing of these signals to be easily separated. by physically separating analogue and digital signals, crosstalk from the pcb can be minimized. use an unbroken solid gnd plane . to achieve best performance from the device, it is advisable to have either a gnd plane layer on a multilayer pcb or to dedicate one side of a 2 layer pcb to be a gnd plane. for double sided implementations it is best to route as many signals as possible on the device mounted side of the board, with the opposite side acting as a gnd plane. the use of a gnd plane greatly reduces any electrical emissions from the pcb and minimizes crosstalk between signals. an evaluation board is available for the wm8521 that demonstrates the above techniques and the excellent performance achievable from the device. this can be ordered or the user manual downloaded from the wolfson web site at www.wolfsonmicro.com
product preview wm8521 w pp rev 1.3 december 2004 19 package drawing notes: a. all linear dimensions are in millimeters (inches). b. this drawing is subject to change without notice. c. body dimensions do not include mold flash or protrusion, not to exceed 0.25mm (0.010in). d. meets jedec.95 ms-012, variation = ab. refer to this specification for further details. symbols dimensions (mm) dimensions (inches) min max min max a 1.35 1.75 0.0532 0.0688 a1 0.10 0.25 0.0040 0.0098 b 0.33 0.51 0.0130 0.0200 c 0.19 0.25 0.0075 0.0098 d 8.55 8.75 0.3367 0.3444 e 3.80 4.00 0.1497 0.1574 e 1.27 bsc 0.05 bsc h 5.80 6.20 0.2284 0.2440 h 0.25 0.50 0.0099 0.0196 l 0.40 1.27 0.0160 0.0500 0 o 8 o 0 o 8 o ref: jedec.95, ms-012 0.10 (0.004) seating plane dm001.c e d: 14 pin soic 3.9mm wide body h b d a a1 c h x 45 o -c- 8 7 1 14 l e
wm8521 product preview w pp rev 1.3 december 2004 20 important notice wolfson microelectronics plc (wm) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current. all products are sold subject to the wm terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. wm warrants performance of its products to the specifications applicable at the time of sale in accordance with wm?s standard warranty. testing and other quality control techniques are utilised to the extent wm deems necessary to support this warranty. specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. in order to minimise risks associated with customer applications, adequate design and operating safeguards must be used by the customer to minimise inherent or procedural hazards. wolfson products are not authorised for use as critical components in life support devices or systems without the express written approval of an officer of the company. life support devices or systems are devices or systems that are intended for surgical implant into the body, or support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided, can be reasonably expected to result in a significant injury to the user. a critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. wm assumes no liability for applications assistance or customer product design. wm does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of wm covering or relating to any combination, machine, or process in which such products or services might be or are used. wm?s publication of information regarding any third party?s products or services does not constitute wm?s approval, license, warranty or endorsement thereof. reproduction of information from the wm web site or datasheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations and notices. representation or reproduction of this information with alteration voids all warranties provided for an associated wm product or service, is an unfair and deceptive business practice, and wm is not responsible nor liable for any such use. resale of wm?s products or services with statements different from or beyond the parameters stated by wm for that product or service voids all express and any implied warranties for the associated wm product or service, is an unfair and deceptive business practice, and wm is not responsible nor liable for any such use. 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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