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BSNandBSPCapacitors
VCLAMPCapacitors
InternalRegulated5-VSupply(AV
DD
)
DifferentialInput
SHUTDOWNOPERATION
USINGLOW-ESRCAPACITORS
TPA3008D2
SLOS435A–MAY2004–REVISEDJULY2004
ThefullH-bridgeoutputstagesuseonlyNMOStransistors.Therefore,theyrequirebootstrapcapacitorsforthe
highsideofeachoutputtoturnoncorrectly.A220-nFceramiccapacitor,ratedforatleast25V,mustbe
connectedfromeachoutputtoitscorrespondingbootstrapinput.Specifically,one220-nFcapacitormustbe
connectedfromxOUTPtoxBSP,andone220-nFcapacitormustbeconnectedfromxOUTNtoxBSN.(Seethe
applicationcircuitdiagraminFigure16.)
ThebootstrapcapacitorsconnectedbetweentheBSxxpinsandcorrespondingoutputfunctionasafloating
powersupplyforthehigh-sideN-channelpowerMOSFETgatedrivecircuitry.Duringeachhigh-sideswitching
cycle,thebootstrapcapacitorsholdthegate-to-sourcevoltagehighenoughtokeepthehigh-sideMOSFETs
turnedon.
Toensurethatthemaximumgate-to-sourcevoltagefortheNMOSoutputtransistorsisnotexceeded,two
internalregulatorsclampthegatevoltage.Two1-µFcapacitorsmustbeconnectedfromVCLAMPL(pin25)and
VCLAMPR(pin36)togroundandmustberatedforatleast25V.ThevoltagesattheVCLAMPterminalsvary
withV
CC
andmaynotbeusedforpoweringanyothercircuitry.
TheAV
DD
terminal(pin29)istheoutputofaninternallygenerated5-Vsupply,usedfortheoscillator,
preamplifier,andvolumecontrolcircuitry.Itrequiresa1-µFcapacitor,placedclosetothepin,tokeepthe
regulatorstable.
ThisregulatedvoltagecanbeusedtocontrolGAIN0andGAIN1terminals,butshouldnotbeusedtodrive
externalcircuitry.
Thedifferentialinputstageoftheamplifiercancelsanynoisethatappearsonbothinputlinesofthechannel.To
usetheTPA3008D2withadifferentialsource,connectthepositiveleadoftheaudiosourcetotheINPinputand
thenegativeleadfromtheaudiosourcetotheINNinput.TousetheTPA3008D2withasingle-endedsource,ac
groundtheINPorINNinputthroughacapacitorequalinvaluetotheinputcapacitoronINNorINPandapply
theaudiosourcetoeitherinput.Inasingle-endedinputapplication,theunusedinputshouldbeacgroundedat
theaudiosourceinsteadofatthedeviceinputforbestnoiseperformance.
TheTPA3008D2employsashutdownmodeofoperationdesignedtoreducesupplycurrent(I
CC
)totheabsolute
minimumlevelduringperiodsofnonuseforpowerconservation.TheSHUTDOWNinputterminalshouldbeheld
high(seespecificationtablefortrippoint)duringnormaloperationwhentheamplifierisinuse.Pulling
SHUTDOWNlowcausestheoutputstomuteandtheamplifiertoenteralow-currentstate.Neverleave
SHUTDOWNunconnected,becauseamplifieroperationwouldbeunpredictable.
Forthebestpower-offpopperformance,placetheamplifierintheshutdownmodepriortoremovingthepower
supplyvoltage.
Low-ESRcapacitorsarerecommendedthroughoutthisapplicationsection.Areal(asopposedtoideal)capacitor
canbemodeledsimplyasaresistorinserieswithanidealcapacitor.Thevoltagedropacrossthisresistor
minimizesthebeneficialeffectsofthecapacitorinthecircuit.Thelowertheequivalentvalueofthisresistance,
themoretherealcapacitorbehaveslikeanidealcapacitor.
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