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w wm7121, WM7121E top port analogue silicon microphone wolfson microelectronics plc to receive regular email updates, sign up at http://www.wolfsonmicro.com/ enews preliminary technical data, october 2012, 2.0 copyright ? 2012 wolfson microelectronics plc description the wm7121 is a low-profile silicon analogue microphone. it offers high signal to noise ratio (snr) and low power consumption and is suited to a wide variety of consumer applications. the wm7121 incorporates wolfson?s proprietary cmos/mems membrane technology, offering high reliability and high performance in a miniature, low-profile package. the wm7121 is designed to withstand the high temperatures associated with automated flow solder assembly processes. (note that conventional microphones can be damaged by this process.) the WM7121E variant offers a tighter tolerance on the microphone sensitivity, givi ng reduced variation between parts. this removes the need for in-line production calibration of part-to-part microphone variations. features ? high snr; selectable sensit ivity tolerance options - wm7121 - snr 65db, sensitivity +/-3db - WM7121E - snr 65db, sensitivity +/-1db ? matched performance to bottom port microphone wm7132 - matched sensitivity performance - matched frequency response - matched phase response ? low supply current 200a ? low profile packaging ? support for automated flow solder assembly ? analogue output ? top port package ? 1.5v to 3.7v supply ? 3.76mm x 2.95mm x 1.10mm package applications ? mobile phone handsets ? portable media players ? digital still cameras ? digital video cameras ? bluetooth headsets ? portable navigation devices ? portable games consoles block diagram wm7121 amp transducer (cmos mems) charge pump vdd output gnd gnd
wm7121 preliminary technical data w ptd, rev 2.0, october 2012 2 table of contents descript ion ....................................................................................................... 1 ? featur es ............................................................................................................ 1 ? applications ..................................................................................................... 1 ? block diag ram ................................................................................................ 1 ? table of co ntents ......................................................................................... 2 ? pin config uration .......................................................................................... 3 ? pin descri ption ................................................................................................ 3 ? ordering info rmation .................................................................................. 3 ? absolute maximu m ratings ........................................................................ 4 ? important assembl y guidel ines .............................................................. 4 ? recommended operatin g condit ions ..................................................... 4 ? acoustic and electrical characteristi cs ......................................... 5 ? terminology ............................................................................................................... 5 ? typical perfo rmance ................................................................................... 6 ? frequency response .............................................................................................. 6 ? thd ratio ..................................................................................................................... . 6? applications in formation .......................................................................... 7 ? recommended external components .............................................................. 7 ? optimised system rf design ................................................................................. 7 ? connection to a wolfs on audio codec .......................................................... 8 ? matched microph one pairs .................................................................................. 9 ? recommended pcb la nd patterns ..................................................................... 9 ? package dime nsions .................................................................................... 10 ? important no tice ......................................................................................... 11 ? address: ..................................................................................................................... 11? revision hi story ........................................................................................... 12 ?
preliminary technical data wm7121 w ptd, rev 2.0, october 2012 3 pin configuration pin description pin name type description 1 vdd supply analogue supply 2 gnd supply analogue ground 3 gnd supply analogue ground 4 output analogue output microphone analogue output signal ordering information device description temperature range moisture sensitivity level peak soldering temperature wm7121ims/v standard -40 to +100 o c msl2a +260 o c wm7121ims/rv standard (tape and reel) -40 to +100 o c msl2a +260 o c wm7121imse/v enhanced -40 to +100 o c msl2a +260 o c wm7121imse/rv enhanced (tape and reel) -40 to +100 o c msl2a +260 o c note: reel quantity = 5000 all devices are pb-free and halogen free.
wm7121 preliminary technical data w ptd, rev 2.0, october 2012 4 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 specificati ons are given under electrical characteristics at the te st 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-st d-020 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. msl2a = out of bag storage for 4 weeks at <30c / 60% re lative 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 specif ied in ordering information. condition min max supply voltage (vdd) -0.3v +4.2v operating temperature range, t a -40oc +100oc storage temperature prior to soldering 30 ? c max / 60% rh max storage temperature after soldering -40oc +100oc important assembly guidelines do not put a vacuum over the port hole of the microphone. pl acing a vacuum over the por t hole can damage the device. do not board wash the microphone after a re-flow process. board washing and the associated cleaning agents can damage the device. do not expose to ultrasonic cleaning methods. do not use a vapour phase re-flow proc ess. the vapour can damage the device. please refer to application note wan0273 fo r further assembly and handling guidelines. recommended operating conditions parameter symbol min typ max unit analogue supply range vdd 1.5 3.7 v ground gnd 0 v
preliminary technical data wm7121 w ptd, rev 2.0, october 2012 5 acoustic and electrical characteristics test conditions: vdd=2.1v, 1khz test signal, t a = 25c parameter symbol test conditions min typ max unit directivity omni-directional sensitivity (wm7121) s 94db spl -41 -38 -35 dbv sensitivity (WM7121E) s 94db spl -39 -38 -37 dbv acoustic overload no load thd < 10% 126 db spl signal to noise ratio snr a-weighted 65 db total harmonic distortion thd 104db spl 0.25 % dynamic range dr a-weighted, noise floor to 1% thd 91 db frequency response -3db low frequency +3db high frequency 62 15000 hz hz acoustic noise floor a-weighted 29 db spl electrical noise floor a-weighted -103 dbv power supply rejection ratio psrr 100mv rms, 217hz 53 db current consumption i vdd 200 a output dc impedance z out 100 ? terminology 1. sensitivity (dbv) ? sensitivity is a measure of the microphone output response to the ac oustic pressure of a 1khz 94db spl (1pa rms) sine wave. 2. signal-to-noise ratio (db) ? snr is a measure of the difference in level bet ween the output response of a 1khz 94db spl sine wave and the idle noise output. 3. total harmonic distortion (db) ? thd is the ratio of the rms sum of the harmonic distor tion products in the specified bandwidth (see note below) relative to the amplit ude of the fundamental (ie. test frequency) output. 4. dynamic range (db) ? dr is the ratio of the 1% thd microphone output level (in response to a sine wave input) and the idle noise output level. 5. all performance measurements are carried out with 20 khz low pass ?brick wall? filter and, where noted, an a-weighted filter. failure to use these filters will result in higher thd and lower snr values than are found in the acoustic and electrical characteristics. the low pass filter removes out of band noise.
wm7121 preliminary technical data w ptd, rev 2.0, october 2012 6 typical performance frequency response \ 10.0 \ 9.0 \ 8.0 \ 7.0 \ 6.0 \ 5.0 \ 4.0 \ 3.0 \ 2.0 \ 1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 10.0 100.0 1000.0 10000.0 100000.0 sensitivity (db) frequency (hz) sensitivity vs frequency (relative to sensitivity @ 1khz) thd ratio
preliminary technical data wm7121 w ptd, rev 2.0, october 2012 7 applications information recommended external components figure 1 wm7121 recommended external components a dc-blocking output capacitor is required on the ou tput pin, as illustrated in figure 1. a single capacitor is required for a singl e-ended connection. the capacitor must be correctly selected as it affects the cut-off frequency of the output path. a lo w cut-off frequency is desirable as it means there is no significant filtering of the audio bandwidth. the 3db cut-off frequency of the output path is gi ven by the equation below, where c is the output capacitance and r is the input re sistance of the other circuit. a typical recommended configuration, with 1uf dc-blocking capacitor and 20k ? minimum input circuit impedance, gives a 3db cut-off frequency of 10hz or less. tantalum electrolytic capacitors are particularly suitable for the dc-blocking components as they offer high stability in a small package size optimised system rf design for optimised rf design please refer to doc ument wan0278 for further information.
wm7121 preliminary technical data w ptd, rev 2.0, october 2012 8 connection to a wolfson audio codec wolfson provides a range of audio codecs in corporating an analogue microphone input interface; these support connection to silicon microphones such as the wm7121. the recommended connection of a wm7121 silicon microphone to the wm8994 is illustrated in figure 2 (for single-ended mode) and figur e 3 (for pseudo-differential mode). a dc blocking capacitor is required, as described in the previous section. a 1f decoupling capacitor is also recommended; this should be positi oned close to the vdd pin of the wm7121. further information on the wm8994 is provided in t he product datasheet, which is available from the wolfson website. the equivalent connections can be made to other wolfson devices in a similar manner. figure 2 wm7121 silicon microphone single-ended connection to wm8994 figure 3 wm7121 silicon microphone pseudo-differential connection to wm8994
preliminary technical data wm7121 w ptd, rev 2.0, october 2012 9 matched microphone pairs wm7121 and wm7132 are sensitivity matched microphone pairs. the enhanced versions, WM7121E and wm7132e have tight tolerance of 1db and compatible output performance. these microphones are ideal for accurate sound pickup from opposite directions in slim profile applications. wm7132e should be positioned close to WM7121E on the same side of the pcb to maximise acoustic matching for effective dsp application. the wm7121 and wm7132 also have matched fr equency response at both high and low frequencies, allowing simplified system design. recommended pcb land patterns 1.70 mm ?0.8 mm figure 4 recommended customer pcb land pattern (note that all other dimensions can be obtained from the package dimensions)
wm7121 preliminary technical data w ptd, rev 2.0, october 2012 10 package dimensions
preliminary technical data wm7121 w ptd, rev 2.0, october 2012 11 important notice wolfson microelectronics plc (?wol fson?) products and services are sold subject to wolfson?s terms and conditions of sale, delivery and payment supplied at the time of order acknowledgement. wolfson warrants performance of its products to the specifications in effect at t he date of shipment. wolfson reserves the right to make changes to its products and s pecifications or to discontinue any produc t or service without notice. customers should therefore obtain the latest version of relevant informati on from wolfson to verify that the information is current. testing and other quality control techniques are utilised to the extent wolfson deems necessary to support its warranty. specific testing of all parameters of each device is not necessarily performed unless requi red by law or regulation. in order to minimise risks associated with customer app lications, the customer must use adequate design and operating safeguards to minimise inherent or proc edural hazards. wolfson is not liable fo r applications assistance or customer product design. the customer is solely responsible for its se lection and use of wolfson products . wolfson is not liable for such selection or use nor for use of any circuitry other than circuitry entirely embodied in a wolfson product. wolfson?s products are not intended for use in life support systems, appliances, nuclear systems or systems where malfunction can reasonably be expected to re sult in personal injury, death or severe property or environmental damage. any use of products by the customer for such purposes is at the customer?s own risk. wolfson does not grant any licence (express or implied) under any patent right, copyright, mask work right or other intellectual property right of wolfson covering or relating to any combination, machine, or pr ocess in which its products or services might be or are used. any prov ision or publication of any third party?s products or services does not constitute wolfson?s approval, licence, warranty or endorsement thereof. any third party trade marks contained in this document belong to the respective third party owner. reproduction of information from wolfson datasheets is per missible only if reproduction is without alteration and is accompanied by all associated copyright, proprietary and other not ices (including this notice) and conditions. wolfson is not liable for any unauthorised alteration of such in formation or for any reliance placed thereon. any representations made, warranties giv en, and/or liabilities accepted by any pers on which differ from those contained in this datasheet or in wolfson?s standard terms and conditions of sale, delivery and payment are made, given and/or accepted at that person?s own risk. wolfson is not liable for any such representations, warranties or liabilities or for any reliance placed thereon by any person. address: wolfson microelectronics plc westfield house 26 westfield road edinburgh eh11 2qb tel :: +44 (0)131 272 7000 fax :: +44 (0)131 272 7001 email :: sales@wolfsonmicro.com
wm7121 preliminary technical data w ptd, rev 2.0, october 2012 12 revision history date rev originator changes 26/09/12 2.0 jmacd first release

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