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1FEATURESAPPLICATIONSDESCRIPTIONTPA3124D2www.
ti.
com.
SLOS578–MAY200815-WSTEREOCLASS-DAUDIOPOWERAMPLIFIERFlatPanelTelevisions23410-W/ChIntoan8-LoadFroma24-VSupplyDLPTVs15-W/Chintoa4-Loadfroma22-VSupplyCRTTVs30-W/Chintoa8-Loadfroma22-VSupplyPoweredSpeakersOperatesFrom10Vto26VCanRunFrom+24VLCDBacklightSupplyEfficientClass-DOperationEliminatesNeedTheTPA3124D2isa15-W(perchannel),efficient,forHeatSinksclass-DaudiopoweramplifierfordrivingstereoFourSelectable,Fixed-GainSettingsspeakersinasingle-endedconfiguration;or,amonoInternalOscillator(NoExternalComponentsspeakerinabridge-tied-loadconfiguration.
TheTPA3124D2candrivestereospeakersaslowas4.
Required)TheefficiencyoftheTPA3124D2eliminatestheneedSingle-EndedAnalogInputsforanexternalheatsinkwhenplayingmusic.
ThermalandShort-CircuitProtectionWithThegainoftheamplifieriscontrolledbytwogainAutoRecoveryselectpins.
Thegainselectionsare20,26,32,andSpace-SavingSurfaceMount24-PinTSSOP36dB.
PackageThepatentedstart-upandshutdownsequencesAdvancedPower-OffPopReductionminimizepopnoiseinthespeakerswithoutadditionalcircuitry.
1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
2DLPisaregisteredtrademarkofTexasInstruments.
3SystemTwo,AudioPrecisionaretrademarksofAudioPrecision,Inc.
4Allothertrademarksarethepropertyoftheirrespectiveowners.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright2008,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
TPA3124D2SLOS578–MAY2008.
www.
ti.
comThesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
PWP(TSSOP)PACKAGE(TOPVIEW)Table1.
TERMINALFUNCTIONSTERMINALI/O/PDESCRIPTION24-PINNAME(PWP)ShutdownsignalforIC(low=disabled,high=operational).
TTLlogiclevelswithcompliancetoSD2IAVCCRIN6IAudioinputforrightchannelLIN5IAudioinputforleftchannelGAIN018IGainselectleast-significantbit.
TTLlogiclevelswithcompliancetoAVCCGAIN117IGainselectmost-significantbit.
TTLlogiclevelswithcompliancetoAVCCMutesignalforquickdisable/enableofoutputs(high=outputsswitchat50%dutycycle,low=MUTE4Ioutputsenabled).
TTLlogiclevelswithcompliancetoAVCCBSL21I/OBootstrapI/OforleftchannelPVCCL1,3PPowersupplyforleft-channelH-bridge,notinternallyconnectedtoPVCCRorAVCCLOUT22OClass-D-H-bridgepositiveoutputforleftchannelPGNDL23,24PPowergroundforleft-channelH-bridgeVCLAMP11PInternallygeneratedvoltagesupplyforbootstrapcapacitorsBSR16I/OBootstrapI/OforrightchannelROUT15OClass-D-H-bridgenegativeoutputforrightchannelPGNDR13,14PPowergroundforright-channelH-bridge.
PVCCR10,12PPowersupplyforright-channelH-bridge,notconnectedtoPVCCLorAVCCAGND9PAnaloggroundfordigital/analogcellsincoreAGND8PAnaloggroundforanalogcellsincoreReferenceforpreamplifierinputs.
NominallyequaltoAVCC/8.
Alsocontrolsstart-uptimeviaBYPASS7Oexternalcapacitorsizing.
AVCC19,20PHigh-voltageanalogpowersupply.
NotinternallyconnectedtoPVCCRorPVCCLConnecttoground.
ThermalpadshouldbesoldereddownonallapplicationstosecuretheThermalpadDiepadPdeviceproperlytotheprintedwiringboard.
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SLOS578–MAY2008overoperatingfree-airtemperaturerange(unlessotherwisenoted)(1)VALUEUNITVCCSupplyvoltageAVCC,PVCC–0.
3to30VVILogicinputvoltageSD,MUTE,GAIN0,GAIN1–0.
3toVCC+0.
3VVINAnaloginputvoltageRIN,LIN–0.
3to7VContinuoustotalpowerdissipationSeeDissipationRatingTableTAOperatingfree-airtemperaturerange–40to85°CTJOperatingjunctiontemperaturerange–40to150°CTstgStoragetemperaturerange–65to150°CSEOutputConfiguration3.
2RLLoadresistance(minimumvalue)BTLOutputConfiguration6.
4Humanbodymodel(allpins)±2kVESDElectrostaticDischargeCharged-devicemodel(all±500Vpins)(1)Stressesbeyondthoselistedunderabsolutemaximumratingsmaycausepermanentdamagetothedevice.
Thesearestressratingsonly,andfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderrecommendedoperatingconditionsisnotimplied.
Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
PACKAGE(1)(2)TA≤25°CDERATINGFACTORTA=70°CTA=85°C24-pinTSSOP4.
16W33.
3mW/°C2.
67W2.
16W(1)Forthemostcurrentpackageandorderinginformation,seethePackageOptionAddendumattheendofthisdocument,orseetheTIwebsiteatwww.
ti.
com.
(2)Thisdatawastakenusing1oztraceandcopperpadthatissoldereddirectlytoaJEDECstandardhigh-kPCB.
Thethermalpadmustbesolderedtoathermallandontheprinted-circuitboard.
SeethePowerPADThermallyEnhancedPackageapplicationnote(SLMA002).
MINMAXUNITVCCSupplyvoltagePVCC,AVCC1026VVIHHigh-levelinputvoltageSD,MUTE,GAIN0,GAIN12VVILLow-levelinputvoltageSD,MUTE,GAIN0,GAIN10.
8VSD,VI=VCC,VCC=30V125IIHHigh-levelinputcurrentMUTE,VI=VCC,VCC=30V125AGAIN0,GAIN1,VI=VCC,VCC=24V125SD,VI=0,VCC=30V1IILLow-levelinputcurrentMUTE,VI=0V,VCC=30V1AGAIN0,GAIN1,VI=0V,VCC=24V1TAOperatingfree-airtemperature–4085°CCopyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback3ProductFolderLink(s):TPA3124D2DCCHARACTERISTICSACCHARACTERISTICSTPA3124D2SLOS578–MAY2008.
www.
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comTA=25°C,VCC=24V,RL=8(unlessotherwisenoted)PARAMETERTESTCONDITIONSMINTYPMAXUNITClass-Doutputoffsetvoltage|VOS|(measureddifferentiallyinBTLVI=0V,AV=36dB7.
550mVmodeasshowninFigure36)V(BYPASS)BypassoutputvoltageNoloadAVCC/8VICC(q)QuiescentsupplycurrentSD=2V,MUTE=0V,noload1630mAICC(q)QuiescentsupplycurrentinMUTE=0.
8V,noload16mAmutemodeICC(q)QuiescentsupplycurrentinSD=0.
8V,noload0.
391mAshutdownmoderDS(on)Drain-sourceon-state450210mresistanceGAIN0=0.
8V182022GAIN1=0.
8VGAIN0=2V242628GGaindBGAIN0=0.
8V303234GAIN=2VGAIN0=2V343638MuteattenuationVI=1Vrms–80dBTA=25°C,VCC=24V,RL=8(unlessotherwisenoted)PARAMETERTESTCONDITIONSMINTYPMAXUNITVCC=24,Vripple=200mVPP100Hz–48ksvrSupplyripplerejectiondBGain=20dB1kHz–52Outputpowerat1%THD+NVCC=24V,f=1kHz8POWOutputpowerat10%THD+NVCC=24V,f=1kHz10Totalharmonicdistortion+f=1kHz,PO=5W0.
04%THD+Nnoise125V20Hzto22kHz,A-weightedfilter,VnOutputintegratednoisefloorGain=20dB–78dBVCrosstalkPO=1W,f=1kHz;gain=20dB–70dBMaxoutputatTHD+N<1%,f=1kHz,SNRSignal-to-noiseratio–92dBgain=20dBThermaltrippoint150°CThermalhysteresis30°CfOSCOscillatorfrequency250300350kHzΔtmuteMutedelayTimefrommuteinputswitcheshighuntil30secoutputsmutedΔtunmuteUnmutedelayTimefrommuteinputswitcheslowuntil120msecoutputsunmuted4SubmitDocumentationFeedbackCopyright2008,TexasInstrumentsIncorporatedProductFolderLink(s):TPA3124D2FUNCTIONALBLOCKDIAGRAMTPA3124D2www.
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SLOS578–MAY2008Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback5ProductFolderLink(s):TPA3124D2TYPICALCHARACTERISTICSTPA3124D2SLOS578–MAY2008.
www.
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comAlltestsaremadeatfrequency=1kHzunlessotherwisenoted.
TOTALHARMONICDISTORTION+NOISETOTALHARMONICDISTORTION+NOISEvsvsFREQUENCYFREQUENCYFigure1.
Figure2.
TOTALHARMONICDISTORTION+NOISETOTALHARMONICDISTORTION+NOISEvsvsFREQUENCYFREQUENCYFigure3.
Figure4.
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SLOS578–MAY2008TYPICALCHARACTERISTICS(continued)Alltestsaremadeatfrequency=1kHzunlessotherwisenoted.
TOTALHARMONICDISTORTION+NOISETOTALHARMONICDISTORTION+NOISEvsvsOUTPUTPOWEROUTPUTPOWERFigure5.
Figure6.
TOTALHARMONICDISTORTION+NOISECROSSTALKvsvsOUTPUTPOWERFREQUENCYFigure7.
Figure8.
Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback7ProductFolderLink(s):TPA3124D2TPA3124D2SLOS578–MAY2008.
www.
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comTYPICALCHARACTERISTICS(continued)Alltestsaremadeatfrequency=1kHzunlessotherwisenoted.
CROSSTALKCROSSTALKvsvsFREQUENCYFREQUENCYFigure9.
Figure10.
GAIN/PHASEGAIN/PHASEvsvsFREQUENCYFREQUENCYFigure11.
Figure12.
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SLOS578–MAY2008TYPICALCHARACTERISTICS(continued)Alltestsaremadeatfrequency=1kHzunlessotherwisenoted.
OUTPUTPOWEROUTPUTPOWERvsvsSUPPLYVOLTAGESUPPLYVOLTAGEFigure14.
A.
Dashedlinerepresentsthermallylimitedregion.
Figure13.
EFFICIENCYEFFICIENCYvsvsOUTPUTPOWEROUTPUTPOWERFigure15.
Figure16.
Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback9ProductFolderLink(s):TPA3124D2TPA3124D2SLOS578–MAY2008.
www.
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comTYPICALCHARACTERISTICS(continued)Alltestsaremadeatfrequency=1kHzunlessotherwisenoted.
SUPPLYCURRENTSUPPLYCURRENTvsvsOUTPUTPOWEROUTPUTPOWERFigure17.
A.
Dashedlinerepresentsthermallylimitedregion.
Figure18.
POWERSUPPLYREJECTIONRATIOPOWERSUPPLYREJECTIONRATIOvsvsFREQUENCYFREQUENCYFigure19.
Figure20.
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SLOS578–MAY2008TYPICALCHARACTERISTICS(continued)Alltestsaremadeatfrequency=1kHzunlessotherwisenoted.
TOTALHARMONICDISTORTION+NOISETOTALHARMONICDISTORTION+NOISEvsvsFREQUENCYOUTPUTPOWERFigure21.
Figure22.
OUTPUTPOWEREFFICIENCYvsvsSUPPLYVOLTAGEOUTPUTPOWERFigure24.
A.
Dashedlinerepresentsthermallylimitedregion.
Figure23.
Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLink(s):TPA3124D2APPLICATIONINFORMATIONCLASS-DOPERATIONTraditionalClass-DModulationSchemeSupplyPumpingTPA3124D2SLOS578–MAY2008.
www.
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comThissectionfocusesontheclass-DoperationoftheTPA3124D2.
TheTPA3124D2operatesinADmode.
Therearetwomainconfigurationsthatmaybeused.
Forstereooperation,theTPA3124D2shouldbeconfiguredinasingle-ended(SE)half-bridgeamplifier.
Formonoapplications,TPA3124D2maybeusedasabridge-tied-load(BTL)amplifier.
Thetraditionalclass-Dmodulationscheme,whichisusedintheTPA3124D2BTLconfiguration,hasadifferentialoutputwhereeachoutputis180degreesoutofphaseandchangesfromgroundtothesupplyvoltage,VCC.
Therefore,thedifferentialprefilteredoutputvariesbetweenpositiveandnegativeVCC,wherefiltered50%dutycycleyields0Vacrosstheload.
Theclass-DmodulationschemewithvoltageandcurrentwaveformsisshowninFigure25andFigure26.
Figure25.
Class-DModulationforTPA3124D2SEConfigurationFigure26.
Class-DModulationforTPA3124D2BTLConfigurationOneissueencounteredinsingle-ended(SE)class-Damplifierdesignsissupplypumping.
Power-supplypumpingisariseinthelocalsupplyvoltageduetoenergybeingdrivenbacktothesupplybyoperationoftheclass-Damplifier.
Thisphenomenonismostevidentatlowaudiofrequenciesandwhenbothchannelsareoperatingatthesamefrequencyandphase.
Atlowlevels,power-supplypumpingresultsindistortionintheaudiooutputduetofluctuationsinsupplyvoltage.
Athigherlevels,pumpingcancausetheovervoltageprotectiontooperate,whichtemporarilyshutsdowntheaudiooutput.
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SLOS578–MAY2008Severalthingscanbedonetorelievepower-supplypumping.
Thelowestimpactistooperatethetwoinputsoutofphase180°andreversethespeakerconnections.
Becausemostaudioishighlycorrelated,thiscausesthesupplypumpingtobeoutofphaseandnotassevere.
Ifthisisnotenough,theamountofbulkcapacitanceonthesupplymustbeincreased.
Also,improvementisrealizedbyhookingothersuppliestothisnode,thereby,sinkingsomeoftheexcesscurrent.
Power-supplypumpingshouldbetestedbyoperatingtheamplifieratlowfrequenciesandhighoutputlevels.
ThegainoftheTPA3124D2issetbytwoinputterminals,GAIN0andGAIN1.
ThegainslistedinTable2arerealizedbychangingthetapsontheinputresistorsandfeedbackresistorsinsidetheamplifier.
Thiscausestheinputimpedance(ZI)tobedependentonthegainsetting.
Theactualgainsettingsarecontrolledbyratiosofresistors,sothegainvariationfrompart-to-partissmall.
However,theinputimpedancefrompart-to-partatthesamegainmayshiftby±20%duetoshiftsintheactualresistanceoftheinputresistors.
Fordesignpurposes,theinputnetwork(discussedinthenextsection)shouldbedesignedassuminganinputimpedanceof8k,whichistheabsoluteminimuminputimpedanceoftheTPA3124D2.
Atthehighergainsettings,theinputimpedancecouldincreaseashighas72k.
Table2.
GainSettingINPUTIMPEDANCEAMPLIFIERGAIN(dB),GAIN1GAIN0(k),TYPICALTYPICAL00206001263010321511369Changingthegainsettingcanvarytheinputresistanceoftheamplifierfromitssmallestvalue,10k±20%,tothelargestvalue,60k±20%.
Asaresult,ifasinglecapacitorisusedintheinputhigh-passfilter,the–3-dBcutofffrequencymaychangewhenchanginggainsteps.
The–3-dBfrequencycanbecalculatedusingEquation1.
UsetheZIvaluesgiveninTable2.
Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback13ProductFolderLink(s):TPA3124D2INPUTCAPACITOR,CI(2)(3)Single-EndedOutputCapacitor,COOutputFilterandFrequencyResponseTPA3124D2SLOS578–MAY2008.
www.
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comInthetypicalapplication,inputcapacitorCIisrequiredtoallowtheamplifiertobiastheinputsignaltotheproperdclevelforoptimumoperation.
InthiscaseCIandtheinputimpedanceoftheamplifier(ZI)formahigh-passfilterwiththecornerfrequencydeterminedinEquation2.
ThevalueofCIisimportant,asitdirectlyaffectsthebass(low-frequency)performanceofthecircuit.
ConsidertheexamplewhereZIis20kandthespecificationcallsforaflatbassresponsedownto20Hz.
Equation2isreconfiguredasEquation3.
Inthisexample,CIis0.
4F;so,onewouldlikelychooseavalueof0.
47Fasthisvalueiscommonlyused.
Ifthegainisknownandisconstant,useZIfromTable2tocalculateCI.
Afurtherconsiderationforthiscapacitoristheleakagepathfromtheinputsourcethroughtheinputnetwork,CI,andthefeedbacknetworktotheload.
Thisleakagecurrentcreatesadcoffsetvoltageattheinputtotheamplifierthatreducesusefulheadroom,especiallyinhigh-gainapplications.
Forthisreason,alow-leakagetantalumorceramiccapacitoristhebestchoice.
Whenpolarizedcapacitorsareused,thepositivesideofthecapacitorshouldfacetheamplifierinputinmostapplicationsasthedclevelthereisheldat2V,whichislikelyhigherthanthesourcedclevel.
Notethatitisimportanttoconfirmthecapacitorpolarityintheapplication.
Additionally,lead-freesoldercancreatedcoffsetvoltages,anditisimportanttoensurethatboardsarecleanedproperly.
Insingle-ended(SE)applications,thedcblockingcapacitorformsahigh-passfilterwiththespeakerimpedance.
Thefrequencyresponserollsoffwithdecreasingfrequencyatarateof20dB/decade.
Thecutofffrequencyisdeterminedbyfc=πCOZLTable3showssomecommoncomponentvaluesandtheassociatedcutofffrequencies:Table3.
CommonFilterResponsesCSE-DCBlockingCapacitor(F)SpeakerImpedance()fc=60Hz(–3dB)fc=40Hz(–3dB)fc=20Hz(–3dB)4680100022006470680150083304701000Forthebestfrequencyresponse,aflat-passbandoutputfilter(second-orderButterworth)maybeused.
TheoutputfiltercomponentsconsistoftheseriesinductorandcapacitortogroundattheLOUTandROUTpins.
Thereareseveralpossibleconfigurations,dependingonthespeakerimpedanceandwhethertheoutputconfigurationissingle-ended(SE)orbridge-tiedload(BTL).
Table4liststherecommendedvaluesforthefiltercomponents.
Itisimportanttouseahigh-qualitycapacitorinthisapplication.
AratingofatleastX7Risrequired.
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SLOS578–MAY2008Table4.
RecommendedFilterOutputComponentsOutputConfigurationSpeakerImpedance()FilterInductor(H)FilterCapacitor(nF)422680SingleEnded(SE)833220BridgeTiedLoad(BTL)822680Figure27.
BTLFilterConfigurationFigure28.
SEFilterConfigurationTheTPA3124D2isahigh-performanceCMOSaudioamplifierthatrequiresadequatepower-supplydecouplingtoensurethattheoutputtotalharmonicdistortion(THD)isaslowaspossible.
Power-supplydecouplingalsopreventsoscillationsforlongleadlengthsbetweentheamplifierandthespeaker.
Theoptimumdecouplingisachievedbyusingtwocapacitorsofdifferenttypesthattargetdifferenttypesofnoiseonthepower-supplyleads.
Forhigher-frequencytransients,spikes,ordigitalhashontheline,agoodlowequivalent-series-resistance(ESR)ceramiccapacitor,typically0.
1Fto1F,placedascloseaspossibletothedeviceVCCleadworksbest.
Forfilteringlowerfrequencynoisesignals,alargeraluminumelectrolyticcapacitorof470Forgreaterplacedneartheaudiopoweramplifierisrecommended.
The470-Fcapacitoralsoservesaslocalstoragecapacitorforsupplyingcurrentduringlargesignaltransientsontheamplifieroutputs.
ThePVCCterminalsprovidethepowertotheoutputtransistors,soa470-ForlargercapacitorshouldbeplacedoneachPVCCterminal.
A10-FcapacitorontheAVCCterminalisadequate.
Thesecapacitorsmustbeproperlyderatedforvoltageandripple-currentratingtoensurereliability.
Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback15ProductFolderLink(s):TPA3124D2BSNandBSPCapacitorsTPA3124D2SLOS578–MAY2008.
www.
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comFigure29.
PSRRWithoutAVCCFilterFigure30.
PSRRWithAVCCFilterFigure31.
ApplicationSchematicwith220-/220-FAVCCFilterThehalfH-bridgeoutputstagesuseonlyNMOStransistors.
Therefore,theyrequirebootstrapcapacitorsforthehighsideofeachoutputtoturnoncorrectly.
A220-nFceramiccapacitor,ratedforatleast25V,mustbeconnectedfromeachoutputtoitscorrespondingbootstrapinput.
Specifically,one220-nFcapacitormustbeconnectedfromLOUTtoBSL,andone220-nFcapacitormustbeconnectedfromROUTtoBSR.
ThebootstrapcapacitorsconnectedbetweentheBSxpinsandtheircorrespondingoutputsfunctionasafloatingpowersupplyforthehigh-sideN-channelpowerMOSFETgate-drivecircuitry.
Duringeachhigh-sideswitchingcycle,thebootstrapcapacitorsholdthegate-to-sourcevoltagehighenoughtokeepthehigh-sideMOSFETsturnedon.
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SLOS578–MAY2008Toensurethatthemaximumgate-to-sourcevoltagefortheNMOSoutputtransistorsisnotexceeded,oneinternalregulatorclampsthegatevoltage.
One1-FcapacitormustbeconnectedfromVCLAMP(pin11)togroundandmustberatedforatleast16V.
ThevoltagesattheVCLAMPterminalmayvarywithVCCandmaynotbeusedforpoweringanyothercircuitry.
Thescaledsupplyreference(VBYP)nominallyprovidesanAVCC/8internalbiasforthepreamplifierstages.
Theexternalcapacitorforthisreference,CBYP,isacriticalcomponentandservesseveralimportantfunctions.
Duringstart-uporrecoveryfromshutdownmode,CBYPdeterminestherateatwhichtheamplifierstarts.
Thestartuptimeisproportionalto0.
5spermicrofarad.
Thus,therecommended1-Fcapacitorresultsinastart-uptimeofapproximately500ms.
Thesecondfunctionistoreducenoiseproducedbythepowersupplycausedbycouplingwiththeoutputdrivesignal.
Thisnoisecouldresultindegradedpower-supplyrejectionandTHD+N.
ThecircuitisdesignedforaCBYPvalueof1Fforbestpopperformance.
Theinputcapacitorsshouldhavethesamevalue.
Aceramicortantalumlow-ESRcapacitorisrecommended.
TheTPA3124D2employsashutdownmodeofoperationdesignedtoreducesupplycurrent(ICC)totheabsoluteminimumlevelduringperiodsofnonuseforpowerconservation.
TheSHUTDOWNinputterminalshouldbeheldhigh(seespecificationtablefortrippoint)duringnormaloperationwhentheamplifierisinuse.
PullingSHUTDOWNlowcausestheoutputstomuteandtheamplifiertoenteralow-currentstate.
NeverleaveSHUTDOWNunconnected,becauseamplifieroperationwouldbeunpredictable.
Forthebestpower-uppopperformance,placetheamplifierintheshutdownormutemodepriortoapplyingthepower-supplyvoltage.
TheMUTEpinisaninputforcontrollingtheoutputstateoftheTPA3124D2.
Alogichighonthisterminalcausestheoutputstorunataconstant50%dutycycle.
Alogiclowonthispinenablestheoutputs.
Thisterminalmaybeusedasaquickdisable/enableofoutputswhenchangingchannelsonatelevisionortransitioningbetweendifferentaudiosources.
TheMUTEterminalshouldneverbeleftfloating.
Forpowerconservation,theSHUTDOWNterminalshouldbeusedtoreducethequiescentcurrenttotheabsoluteminimumlevel.
Low-ESRcapacitorsarerecommendedthroughoutthisapplicationsection.
Areal(asopposedtoideal)capacitorcanbemodeledsimplyasaresistorinserieswithanidealcapacitor.
Thevoltagedropacrossthisresistorminimizesthebeneficialeffectsofthecapacitorinthecircuit.
Thelowertheequivalentvalueofthisresistance,themoretherealcapacitorbehaveslikeanidealcapacitor.
TheTPA3124D2hasshort-circuitprotectioncircuitryontheoutputsthatpreventsdamagetothedeviceduringoutput-to-outputshortsandoutput-to-GNDshortsafterthefilterandoutputcapacitor(atthespeakerterminal.
)Directlyatthedeviceterminals,theprotectioncircuitrypreventsdamagetodeviceduringoutput-to-output,output-to-ground,andoutput-to-supply.
Whenashortcircuitisdetectedontheoutputs,thepartimmediatelydisablestheoutputdrive.
Thisisanunlatchedfault.
Normaloperationisrestoredwhenthefaultisremoved.
Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback17ProductFolderLink(s):TPA3124D2THERMALPROTECTIONPRINTED-CIRCUITBOARD(PCB)LAYOUTTPA3124D2SLOS578–MAY2008.
www.
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comThermalprotectionontheTPA3124D2preventsdamagetothedevicewhentheinternaldietemperatureexceeds150°C.
Thereisa±15°Ctoleranceonthistrippointfromdevicetodevice.
Oncethedietemperatureexceedsthethermalsetpoint,thedeviceentersintotheshutdownstateandtheoutputsaredisabled.
Thisisnotalatchedfault.
Thethermalfaultisclearedoncethetemperatureofthedieisreducedby30°C.
Thedevicebeginsnormaloperationatthispointwithnoexternalsysteminteraction.
BecausetheTPA3124D2isaclass-Damplifierthatswitchesatahighfrequency,thelayoutoftheprinted-circuitboard(PCB)shouldbeoptimizedaccordingtothefollowingguidelinesforthebestpossibleperformance.
Decouplingcapacitors—Thehigh-frequency0.
1-FdecouplingcapacitorsshouldbeplacedasclosetothePVCC(pins1,3,10,and12)andAVCC(pins19and20)terminalsaspossible.
TheVBYP(pin7)capacitorandVCLAMP(pin11)capacitorshouldalsobeplacedasclosetothedeviceaspossible.
Large(220-Forgreater)bulkpower-supplydecouplingcapacitorsshouldbeplacedneartheTPA3124D2onthePVCCLandPVCCRterminals.
Grounding—TheAVCC(pins19and20)decouplingcapacitorandVBYP(pin7)capacitorshouldeachbegroundedtoanalogground(AGND,pins8and9).
ThePVCCxdecouplingcapacitorsandVCLAMPcapacitorsshouldeachbegroundedtopowerground(PGND,pins13,14,23,and24).
Analoggroundandpowergroundshouldbeconnectedatthethermalpad,whichshouldbeusedasacentralgroundconnectionorstargroundfortheTPA3124D2.
Outputfilter—Thereconstructionfilter(L1,L2,C9,andC16)shouldbeplacedasclosetotheoutputterminalsaspossibleforthebestEMIperformance.
Thecapacitorsshouldbegroundedtopowerground.
Thermalpad—ThethermalpadmustbesolderedtothePCBforproperthermalperformanceandoptimalreliability.
Thedimensionsofthethermalpadandthermallandaredescribedinthemechanicalsectionatthebackofthedatasheet.
SeeTITechnicalBriefsSLMA002andSLOA120formoreinformationaboutusingthethermalpad.
ForrecommendedPCBfootprints,seefiguresattheendofthisdatasheet.
Foranexamplelayout,seetheTPA3124D2EvaluationModule(TPA3124D2EVM)UserManual,(SLOU189).
BoththeEVMusermanualandthethermalpadapplicationnoteareavailableontheTIWebsiteathttp://www.
ti.
com.
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SLOS578–MAY2008Figure32.
SchematicforSingle-Ended(SE)Configuration(8-Speaker)Figure33.
SchematicforBridge-Tied-Load(BTL)Configuration(8-Speaker)Copyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback19ProductFolderLink(s):TPA3124D2BASICMEASUREMENTSYSTEMTPA3124D2SLOS578–MAY2008.
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comThissectionfocusesonmethodsthatusethebasicequipmentlistedbelow:AudioanalyzerorspectrumanalyzerDigitalmultimeter(DMM)OscilloscopeTwisted-pairwiresSignalgeneratorPowerresistor(s)LinearregulatedpowersupplyFiltercomponentsEVMorothercompleteaudiocircuitFigure34showstheblockdiagramsofbasicmeasurementsystemsforclass-ABandclass-Damplifiers.
Asinewaveisnormallyusedastheinputsignalbecauseitconsistsofthefundamentalfrequencyonly(nootherharmonicsarepresent).
Ananalyzeristhenconnectedtotheaudiopoweramplifier(APA)outputtomeasurethevoltageoutput.
Theanalyzermustbecapableofmeasuringtheentireaudiobandwidth.
AregulateddcpowersupplyisusedtoreducethenoiseanddistortioninjectedintotheAPAthroughthepowerpins.
ASystemTwoaudiomeasurementsystem(AP-II)byAudioPrecisionincludesthesignalgeneratorandanalyzerinonepackage.
Thegeneratoroutputandamplifierinputmustbeac-coupled.
However,theEVMsalreadyhavetheac-couplingcapacitorsCIN,sonoadditionalcouplingisrequired.
Thegeneratoroutputimpedanceshouldbelowtoavoidattenuatingthetestsignal,andisimportantbecausetheinputresistanceofAPAsisnothigh.
Conversely,theanalyzerinputimpedanceshouldbehigh.
Theoutputresistance,ROUT,oftheAPAisnormallyinthehundredsofmilliohmsandcanbeignoredforallbutthepower-relatedcalculations.
Figure34(a)showsaclass-ABamplifiersystem.
Ittakesananalogsignalinputandproducesananalogsignaloutput.
ThisamplifiercircuitcanbedirectlyconnectedtotheAP-IIorotheranalyzerinput.
Thisisnottrueoftheclass-DamplifiersystemshowninFigure34(b),whichrequireslow-passfiltersinmostcasesinordertomeasuretheaudiooutputwaveforms.
Thisisbecauseittakesananaloginputsignalandconvertsitintoapulse-widthmodulated(PWM)outputsignalthatisnotaccuratelyprocessedbysomeanalyzers.
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SLOS578–MAY2008Figure34.
AudioMeasurementSystemsCopyright2008,TexasInstrumentsIncorporatedSubmitDocumentationFeedback21ProductFolderLink(s):TPA3124D2SEInputandSEOutput(TPA3124D2StereoConfiguration)TPA3124D2SLOS578–MAY2008.
www.
ti.
comTheSEinputandoutputconfigurationisusedwithclass-ABamplifiers.
AblockdiagramofafullySEmeasurementcircuitisshowninFigure35.
SEinputsnormallyhaveoneinputpinperchannel.
Insomecases,twopinsarepresent;oneisthesignalandtheotherisground.
SEoutputshaveonepindrivingaloadthroughanoutputac-couplingcapacitorandtheotherendoftheloadistiedtoground.
SEinputsandoutputsareconsideredtobeunbalanced,meaningoneendistiedtogroundandtheothertoanamplifierinput/output.
Thegeneratorshouldhaveunbalancedoutputs,andthesignalshouldbereferencedtothegeneratorgroundforbestresults.
Unbalancedorbalancedoutputscanbeusedwhenfloating,buttheymaycreateagroundloopthataffectsthemeasurementaccuracy.
Theanalyzershouldhavebalancedinputstocanceloutanycommon-modenoiseinthemeasurement.
Figure35.
SEInput—SEOutputMeasurementCircuitThefollowinggeneralrulesshouldbefollowedwhenconnectingtoAPAswithSEinputsandoutputs:Useanunbalancedsourcetosupplytheinputsignal.
Useananalyzerwithbalancedinputs.
Usetwisted-pairwireforallconnections.
Useshieldingwhenthesystemenvironmentisnoisy.
EnsurethecablesfromthepowersupplytotheAPA,andfromtheAPAtotheload,canhandlethelargecurrents(seeTable5).
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SLOS578–MAY2008Manyoftheclass-DAPAsandmanyclass-ABAPAshavedifferentialinputsandbridge-tied-load(BTL)outputs.
Differentialinputshavetwoinputpinsperchannelandamplifythedifferenceinvoltagebetweenthepins.
Differentialinputsreducethecommon-modenoiseanddistortionoftheinputcircuit.
BTLisatermcommonlyusedinaudiotodescribedifferentialoutputs.
BTLoutputshavetwooutputpinsprovidingvoltagesthatare180°outofphase.
Theloadisconnectedbetweenthesepins.
Thishastheaddedbenefitsofquadruplingtheoutputpowertotheloadandeliminatingadc-blockingcapacitor.
AblockdiagramofthemeasurementcircuitisshowninFigure36.
Thedifferentialinputisabalancedinput,meaningthepositive(+)andnegative(–)pinshavethesameimpedancetoground.
Similarly,theSEoutputequatestoabalancedoutput.
Figure36.
DifferentialInput,BTLOutputMeasurementCircuitThegeneratorshouldhavebalancedoutputs,andthesignalshouldbebalancedforbestresults.
Anunbalancedoutputcanbeused,butitmaycreateagroundloopthataffectsthemeasurementaccuracy.
Theanalyzermustalsohavebalancedinputsforthesystemtobefullybalanced,therebycancellingoutanycommon-modenoiseinthecircuitandprovidingthemostaccuratemeasurement.
ThefollowinggeneralrulesshouldbefollowedwhenconnectingtoAPAswithdifferentialinputsandBTLoutputs:Useabalancedsourcetosupplytheinputsignal.
Useananalyzerwithbalancedinputs.
Usetwisted-pairwireforallconnections.
Useshieldingwhenthesystemenvironmentisnoisy.
EnsurethatthecablesfromthepowersupplytotheAPA,andfromtheAPAtotheload,canhandlethelargecurrents(seeTable5).
Table5showstherecommendedwiresizeforthepowersupplyandloadcablesoftheAPAsystem.
Therealconcernisthedcoracpowerlossthatoccursasthecurrentflowsthroughthecable.
Theserecommendationsarebasedon12-inch(30.
5-cm)-longwirewitha20-kHzsine-wavesignalat25°C.
Table5.
RecommendedMinimumWireSizeforPowerCablesDCPOWERLOSSACPOWERLOSSPOUT(W)RL()AWGSize(mW)(mW)1041822164018422418223.
283.
78.
5182228282.
18.
1<0.
75822281.
56.
11.
66.
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016.
46.
958.
31.
68.
016.
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0367.
038.
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com14-Jul-2012PackMaterials-Page2IMPORTANTNOTICETexasInstrumentsIncorporatedanditssubsidiaries(TI)reservetherighttomakecorrections,enhancements,improvementsandotherchangestoitssemiconductorproductsandservicesperJESD46,latestissue,andtodiscontinueanyproductorserviceperJESD48,latestissue.
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