Datasheet

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End-Points
ClockandReset
DigitalAudioInterface(PCM2902)
SupportedInputData(PCM2902)
PCM2900
PCM2902
SLES035E–MARCH2007–REVISEDMARCH2008
ThePCM2900/2902hasthefollowingfourend-points.
•Controlend-point(EP#0)
•Isochronous-outaudiodatastreamend-point(EP#2)
•Isochronous-inaudiodatastreamend-point(EP#4)
•HIDend-point(EP#5)
Thecontrolend-pointisadefaultend-point.Thecontrolend-pointisusedtocontrolallfunctionsofthe
PCM2900/2902bythestandardUSBrequestandUSBaudioclassspecificrequestfromthehost.The
isochronous-outaudiodatastreamend-pointisanaudiosinkend-point,whichreceivesthePCMaudiodata.The
isochronous-outaudiodatastreamend-pointacceptstheadaptivetransfermode.Theisochronous-inaudiodata
streamend-pointisanaudiosourceend-point,whichtransmitsthePCMaudiodata.Theisochronous-inaudio
datastreamend-pointusesasynchronoustransfermode.TheHIDend-pointisaninterrupt-inend-point.HID
end-pointreportsHID0,HID1,andHID2pinstatusevery32ms.
Thehumaninterfacedevice(HID)pinsaredefinedasconsumercontroldevices.TheHIDfunctionisdesigned
asanindependentend-pointfrombothisochronous-inand-outend-points.Thismeansthattheresultof
affectionfortheHIDoperationdependsonthehostsoftware.Typically,theHIDfunctionisaffectedforthe
primaryaudio-outdevice.
ThePCM2900/2902requiresa12-MHz(±500ppm)clockfortheUSBandaudiofunction,whichcanbe
generatedbyabuilt-incrystaloscillatorwitha12-MHzcrystalresonator.The12-MHzcrystalresonatormustbe
connectedtoXTI(pin21)andXTO(pin20)withonehigh(1-MΩ)resistorandtwosmallcapacitors,the
capacitanceofwhichdependsontheloadcapacitanceofthecrystalresonator.Theexternalclockcanbe
suppliedfromXTI(pin21).Iftheexternalclockissupplied,XTO(pin20)mustbeleftopen.Becauseofno
clock-disablingsignal,itisnotrecommendedtousetheexternalclocksupply.SSPND(pin28)isunabletouse
clockdisabling.
ThePCM2900/2902hasaninternalpower-onresetcircuit,whichworksautomaticallywhenV
BUS
(pin3)exceeds
2.5Vtypical(2.7V–2.2V),andabout700µsisrequireduntilinternalresetrelease.
ThePCM2902employsbothS/PDIFinputandoutput.Isochronous-outdatafromthehostisencodedtothe
S/PDIFoutputandtheDACanalogoutput.InputdataisselectedaseitherS/PDIForADCanaloginput.When
thedevicedetectsanS/PDIFinputandsuccessfullylocksthereceiveddata,theisochronous-intransferdata
sourceisautomaticallyselectedfromS/PDIFitself;otherwise,thedatasourceisselectedtoADCanaloginput.
ThefollowingdataformatsareacceptedbytheS/PDIFinputandoutput.Allotherdataformatsareunabletouse
S/PDIF.
•48-kHz16-bitstereo
•44.1-kHz16-bitstereo
•32-kHz16-bitstereo
Mismatchbetweeninputdataformatandhostcommandmaycauseunexpectedresultsexceptinthefollowing
conditions.
•Recordmonauralformatfromstereodatainputatthesamedatarate
•Record8-bitformatfrom16-bitdatainputatthesamedatarate
Acombinationbetweentheaboveconditionsisnotaccepted.
Fortheplayback,allpossibledataratesourceisconvertedto16-bitstereoformatatthesamesourcedatarate.
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ProductFolderLink(s):PCM2900PCM2902
Not Recommended for New Designs