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•••
FullySpecifiedfor3.3-Vand5-VOperationWidePowerSupplyCompatibility2.5V–5.5V
OutputPowerforRL=8Ω–350mWatVDD=5V–250mWatVDD=3.3V
UltralowSupplyCurrentinShutdownMode...0.15µA
ThermalandShort-CircuitProtectionSurface-MountPackaging–SOIC
–PowerPAD™MSOP
D OR DGN PACKAGE
(TOP VIEW)
•••
SHUTDOWNBYPASSIN+IN-12348765VO-GNDVDDVO+
DESCRIPTION
TheTPA321isabridge-tiedload(BTL)audiopoweramplifierdevelopedespeciallyforlow-voltageapplicationswhereinternalspeakersarerequired.Operatingwitha3.3-Vsupply,theTPA321candeliver250mWofcontinuouspowerintoaBTL8-Ωloadatlessthan1%THD+Nthroughoutvoicebandfrequencies.Althoughthisdeviceischaracterizedoutto20kHz,itsoperationwasoptimizedfornarrowerbandapplicationssuchascellularcommunications.TheBTLconfigurationeliminatestheneedforexternalcouplingcapacitorsontheoutputinmostapplications,whichisparticularlyimportantforsmallbattery-poweredequipment.Thisdevicefeaturesashutdownmodeforpower-sensitiveapplicationswithaquiescentcurrentof0.15µAduringshutdown.TheTPA321isavailableinan8-pinSOICsurface-mountpackageandthesurface-mountPowerPAD™MSOP,whichreducesboardspaceby50%andheightby40%.
VDD6RFAudio InputVDD/2RICI43IN-IN+VO+5CS1 µFVDD
-+2CB0.1 µFBYPASS-+VO-87350 mWGNDFrom System Control1SHUTDOWNBiasControlPleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
PowerPADisatrademarkofTexasInstruments.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.ProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
Copyright©2000–2004,TexasInstrumentsIncorporated
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ThisintegratedcircuitcanbedamagedbyESD.TexasInstrumentsrecommendsthatallintegratedcircuitsbehandledwithappropriateprecautions.Failuretoobserveproperhandlingandinstallationprocedurescancausedamage.
ESDdamagecanrangefromsubtleperformancedegradationtocompletedevicefailure.Precisionintegratedcircuitsmaybemoresusceptibletodamagebecauseverysmallparametricchangescouldcausethedevicenottomeetitspublishedspecifications.
AVAILABLEOPTIONS
TA–40°Cto85°C(1)
PACKAGEDDEVICESSMALLOUTLINE(1)(D)TPA321DMSOP(1)(DGN)TPA321DGNMSOPSYMBOLIZATIONAJBTheDandDGNpackagesareavailabletapedandreeled.Toorderatapedandreeledpart,addthesuffixRtothepartnumber(e.g.,TPA321DR).
overoperatingfree-airtemperaturerange(unlessotherwisenoted)(1)
UNITVDDVITATJTstg(1)
SupplyvoltageInputvoltageContinuoustotalpowerdissipationOperatingfree-airtemperaturerangeOperatingjunctiontemperaturerangeStoragetemperaturerangeLeadtemperature1,6mm(1/16inch)fromcasefor10seconds6V–0.3VtoVDD+0.3VInternallylimited(seeDissipationRatingTable)–40°Cto85°C–40°Cto150°C–65°Cto150°C260°CStressesbeyondthoselistedunder\"absolutemaximumratings\"maycausepermanentdamagetothedevice.Thesearestressratingsonly,andfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunder\"recommendedoperatingconditions\"isnotimplied.Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
PACKAGEDDGN(1)
TA≤25°C725mW2.14W(1)DERATINGFACTOR5.8mW/°C17.1mW/°CTA=70°C464mW1.37WTA=85°C377mW1.11WSeetheTexasInstrumentsdocument,PowerPADThermallyEnhancedPackageApplicationReport(literaturenumberSLMA002),formoreinformationonthePowerPAD™package.ThethermaldatawasmeasuredonaPCBlayoutbasedontheinformationinthesectionentitledTexasInstrumentsRecommendedBoardforPowerPADonpage33ofthebeforementioneddocument.
MINVDDVIHVILTASupplyvoltageHigh-levelvoltageLow-levelvoltageSHUTDOWNSHUTDOWN–402.50.9VDDMAX5.50.1VDD85UNITVVV°COperatingfree-airtemperature2
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ELECTRICALCHARACTERISTICS
atspecifiedfree-airtemperature,VDD=3.3V,TA=25°C(unlessotherwisenoted)
PARAMETER|VOO|PSRRIDDIDD(SD)|IIH||IIL|Outputoffsetvoltage(measureddifferentially)PowersupplyrejectionratioSupplycurrent(seeFigure3)Supplycurrent,shutdownmode(seeFigure4)High-levelinputcurrentLow-levelinputcurrentTESTCONDITIONSSHUTDOWN=0V,RL=8Ω,RF=10kΩVDD=3.2Vto3.4VSHUTDOWN=0V,RF=10kΩSHUTDOWN=VDD,RF=10kΩSHUTDOWN,VDD=3.3V,VI=3.3VSHUTDOWN,VDD=3.3V,VI=0VMINTYPMAX5850.70.151.551120UNITmVdBmAµAµAµAOPERATINGCHARACTERISTICS
VDD=3.3V,TA=25°C,RL=8Ω
PARAMETERPOTHD+NOutputpower(1)TotalharmonicdistortionplusnoiseMaximumoutputpowerbandwidthB1Unity-gainbandwidthSupplyripplerejectionratioVn(1)
NoiseoutputvoltageTHD=0.5%,PO=250mW,AV=-2V/V,Openloop,AV=–1V/V,RL=32Ω,TESTCONDITIONSSeeFigure9f=20Hzto4kHz,SeeFigure7SeeFigure15CB=0.1µF,SeeFigure19MINTYPMAX2501.3%101.47115kHzMHzdBµV(rms)UNITmWAV=-2V/V,THD=3%,SeeFigure7f=1kHz,CB=1µF,SeeFigure2Outputpowerismeasuredattheoutputterminalsofthedeviceatf=1kHz.
ELECTRICALCHARACTERISTICS
atspecifiedfree-airtemperature,VDD=5V,TA=25°C(unlessotherwisenoted)
PARAMETER|VOO|PSRRIDDIDD(SD)|IIH||IIL|Outputoffsetvoltage(measureddifferentially)PowersupplyrejectionratioSupplycurrent(seeFigure3)Supplycurrent,shutdownmode(seeFigure4)High-levelinputcurrentLow-levelinputcurrentTESTCONDITIONSSHUTDOWN=0V,RL=8Ω,RF=10kΩVDD=4.9Vto5.1VSHUTDOWN=0V,RF=10kΩSHUTDOWN=VDD,RF=10kΩSHUTDOWN,VDD=5.5V,VI=VDDSHUTDOWN,VDD=5.5V,VI=0VMINTYPMAX5780.70.151.551120UNITmVdBmAµAµAµAOPERATINGCHARACTERISTICS
VDD=5V,TA=25°C,RL=8Ω
PARAMETERPOTHD+NOutputpowerTotalharmonicdistortionplusnoiseMaximumoutputpowerbandwidthB1Unity-gainbandwidthSupplyripplerejectionratioVnNoiseoutputvoltageTHD=0.5%,PO=350mW,AV=–2V/V,Openloop,AV=-1V/V,RL=32Ω,TESTCONDITIONSSeeFigure13f=20Hzto4kHz,SeeFigure11SeeFigure16CB=0.1µF,SeeFigure20MINTYPMAX7001%101.46515kHzMHzdBµV(rms)UNITmWAV=–2V/V,THD=2%,SeeFigure11f=1kHz,CB=1µF,SeeFigure23
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TerminalFunctions
TERMINALNAMEBYPASSGNDIN-IN+SHUTDOWNVDDVO+VO-NO.27431658OOIIII/OIDESCRIPTIONBYPASSisthetaptothevoltagedividerforinternalmid-supplybias.Thisterminalshouldbeconnectedtoa0.1-µFto1-µFcapacitorwhenusedasanaudioamplifier.GNDisthegroundconnection.IN-istheinvertinginput.IN-istypicallyusedastheaudioinputterminal.IN+isthenoninvertinginput.IN+istypicallytiedtotheBYPASSterminalforSEoperations.SHUTDOWNplacestheentiredeviceinshutdownmodewhenheldhigh(IDD~0.15µA).VDDisthesupplyvoltageterminal.VO+isthepositiveBTLoutput.VO-isthenegativeBTLoutput.PARAMETERMEASUREMENTINFORMATION
VDD6RFAudio InputRICIVDD/243IN-IN+VO+5CS1 µFVDD
-+2CB0.1 µFBYPASSRL = 8 Ω-+VO-87GND1SHUTDOWNBiasControlFigure1.TestCircuit
4
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TYPICALCHARACTERISTICS
TableofGraphs
FIGUREkSVRIDDPOTHD+NSupplyvoltagerejectionratioSupplycurrentOutputpowerTotalharmonicdistortionplusnoiseOpen-loopgainandphaseClosed-loopgainandphaseVnPDOutputnoisevoltagePowerdissipationvsFrequencyvsSupplyvoltagevsSupplyvoltagevsLoadresistancevsFrequencyvsOutputpowervsFrequencyvsFrequencyvsFrequencyvsOutputpower23,4567,8,11,129,10,13,1415,1617,1819,2021,22SUPPLYVOLTAGEREJECTIONRATIO
vs
FREQUENCY
0kSVR− Supply Voltage Rejection Ratio − dB−10−20−30−40−50−60−70−80−90−100201001 kf − Frequency − Hz
10 k20 k−0.123VDD = 3.3 VVDD = 5 VRL = 8 ΩCB = 1 µF0.9IDD− Supply Current − mA1.1SUPPLYCURRENT
vs
SUPPLYVOLTAGE
SHUTDOWN = 0 VRF = 10 kΩ0.70.50.30.1456VDD − Supply Voltage − V
Figure2.Figure3.
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SUPPLYCURRENT(SHUTDOWN)
vs
SUPPLYVOLTAGE0.50.45IDD(SD)− Supply Current − µA0.40.350.30.250.20.150.10.05SHUTDOWN = VDDRF = 10 kΩ22.533.544.555.5VDD − Supply Voltage − V
Figure4.
OUTPUTPOWER
vs
SUPPLYVOLTAGE1000THD+N 1%800PO− Output Power − mW600RL = 8 Ω400RL = 32 Ω200022.533.544.555.5VDD − Supply Voltage − V
Figure5.
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OUTPUTPOWER
vs
LOADRESISTANCE800THD+N = 1%700PO− Output Power − mW600VDD = 5 V5004003002001000VDD = 3.3 V816243240485664RL − Load Resistance − Ω
Figure6.
TOTALHARMONICDISTORTION+NOISE
vs
FREQUENCY
10THD+N −Total Harmonic Distortion + Noise − %AV = −20 V/VTHD+N −Total Harmonic Distortion + Noise − %VDD = 3.3 VPO = 250 mWRL = 8 Ω10TOTALHARMONICDISTORTION+NOISE
vs
FREQUENCY
VDD = 3.3 VRL = 8 ΩAV = −2 V/VPO = 50 mW11AV =− 10 V/VAV = −2 V/V0.1PO = 125 mW0.10.01201001kf − Frequency − Hz
10k20k0.0120PO = 250 mW1001kf − Frequency − Hz
10k20kFigure7.Figure8.
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TOTALHARMONICDISTORTION+NOISE
vs
OUTPUTPOWER
10THD+N −Total Harmonic Distortion + Noise − %VDD = 3.3 Vf = 1 kHzAV = −2 V/V1THD+N −Total Harmonic Distortion + Noise − %10TOTALHARMONICDISTORTION+NOISE
vs
OUTPUTPOWER
f = 20 kHzf = 10 kHz1f = 1 kHzRL = 8 Ω0.10.1f = 20 HzVDD = 3.3 VRL = 8 ΩAV = −2 V/V0.1PO − Output Power − W
10.010.040.10.160.220.280.340.40.010.01PO − Output Power − W
Figure9.
TOTALHARMONICDISTORTION+NOISE
vs
FREQUENCY
10THD+N −Total Harmonic Distortion + Noise − %AV = −20 V/VTHD+N −Total Harmonic Distortion + Noise − %VDD = 5 VPO = 350 mWRL = 8 Ω10VDD = 5 VRL = 8 ΩAV = −2 V/VFigure10.
TOTALHARMONICDISTORTION+NOISE
vs
FREQUENCY
PO = 50 mW11AV =− 10 V/V0.1AV = −2 V/VPO = 175 mW0.1PO = 350 mW0.01201001kf − Frequency − Hz
10k20k0.01201001kf − Frequency − Hz
10k20kFigure11.Figure12.
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TOTALHARMONICDISTORTION+NOISE
vs
OUTPUTPOWER
10THD+N −Total Harmonic Distortion + Noise − %VDD = 5 Vf = 1 kHzAV = −2 V/V1RL = 8 ΩTHD+N −Total Harmonic Distortion + Noise − %10TOTALHARMONICDISTORTION+NOISE
vs
OUTPUTPOWER
f = 20 kHzf = 10 kHz1f = 1 kHz0.10.1f = 20 HzVDD = 5 VRL = 8 ΩAV = −2 V/V0.010.10.250.400.550.700.8510.010.010.1PO − Output Power − W
1PO − Output Power − W
Figure13.
OPEN-LOOPGAINANDPHASE
vs
FREQUENCY
Phase30GainOpen-Loop Gain − dB2060
100
0−10−20−301−60
VDD = 3.3 VRL = Open180
Figure14.
40120
−120
101102f − Frequency − kHz
103104−180
Figure15.
Phase −°9
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4030OPEN-LOOPGAINANDPHASE
vs
FREQUENCY
PhaseGainVDD = 5 VRL = Open180
120
Open-Loop Gain − dB2060
100
0−10−20−301−60
Phase −°Phase −°−120
101102f − Frequency − kHz
103104−180
Figure16.
CLOSED-LOOPGAINANDPHASE
vs
FREQUENCY10.750.5Closed-Loop Gain − dB0.250−0.25−0.5−0.75−1−1.25−1.5−1.75−2101VDD = 3.3 VRL = 8 ΩPO = 0.25 WCI =1 µF102103104105106140
Gain150160
Phase170180
130
120
f − Frequency − Hz
Figure17.
10
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CLOSED-LOOPGAINANDPHASE
vs
FREQUENCY10.750.5Closed-Loop Gain − dB0.250−0.25−0.5−0.75−1−1.25−1.5−1.75−2101VDD = 5 VRL = 8 ΩPO = 0.35 WCI =1 µF102103104105140
Gain150
Phase −°VO BTLVO+1 kf − Frequency − Hz160
Phase170180
130
120106f − Frequency − Hz
Figure18.
OUTPUTNOISEVOLTAGE
vs
FREQUENCY
100Vn− Output Noise Voltage −µV(rms)VDD = 3.3 VBW = 22 Hz to 22 kHzRL = 32 ΩCB =0.1 µFAV = −1 V/VVO BTL100Vn− Output Noise Voltage −µV(rms)OUTPUTNOISEVOLTAGE
vs
FREQUENCY
VDD = 5 VBW = 22 Hz to 22 kHzRL = 32 ΩCB =0.1 µFAV = −1 V/V10VO+101201001 kf − Frequency − Hz
10 k20 k12010010 k20 kFigure19.Figure20.
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POWERDISSIPATION
vs
OUTPUTPOWER
300270PD− Power Dissipation − mW24021018015012090VDD = 3.3 VRL = 8 ΩPD− Power Dissipation − mW720640560480400320240160POWERDISSIPATION
vs
OUTPUTPOWER
VDD = 5 VRL = 8 Ω0200400600800100012000100200300400PO − Output Power − mWPO − Output Power − mW
Figure21.Figure22.
12
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APPLICATIONINFORMATION
BRIDGE-TIEDLOAD
Figure23showsalinearaudiopoweramplifier(APA)inaBTLconfiguration.TheTPA321BTLamplifierconsistsoftwolinearamplifiersdrivingbothendsoftheload.Thereareseveralpotentialbenefitstothisdifferentialdriveconfigurationbutpowertotheloadshouldbeinitiallyconsidered.Thedifferentialdrivetothespeakermeansthatasonesideisslewingup,theothersideisslewingdown,andviceversa.This,ineffect,doublesthevoltageswingontheloadascomparedtoaground-referencedload.Plugging2×VO(PP)intothepowerequation,wherevoltageissquared,yields4×theoutputpowerfromthesamesupplyrailandloadimpedance(seeEquation1).
VO(PP)
V(RMS)+
2Ǹ2
Power+
V(RMS)RL
VDD2
(1)
VO(PP)
RLVDD2x VO(PP)
-VO(PP)
Figure23.Bridge-TiedLoadConfiguration
Inatypicalportablehandheldequipmentsoundchanneloperatingat3.3V,bridgingraisesthepowerintoan8-Ωspeakerfromasingle-ended(SE,groundreference)limitof62.5mWto250mW.Insoundpowerthatisa6-dBimprovement,whichisloudnessthatcanbeheard.Inadditiontoincreasedpower,therearefrequencyresponseconcerns.Considerthesingle-supplySEconfigurationshowninFigure24.Acouplingcapacitorisrequiredtoblockthedcoffsetvoltagefromreachingtheload.Thesecapacitorscanbequitelarge(approximately33µFto1000µF)sotheytendtobeexpensive,heavy,occupyvaluablePCBarea,andhavetheadditionaldrawbackoflimitinglow-frequencyperformanceofthesystem.ThisfrequencylimitingeffectisduetothehighpassfilternetworkcreatedwiththespeakerimpedanceandthecouplingcapacitanceandiscalculatedwithEquation2.
1fc+
2pRLCC
(2)Forexample,a68-µFcapacitorwithan8-Ωspeakerwouldattenuatelowfrequenciesbelow293Hz.TheBTLconfigurationcancelsthedcoffsets,eliminatingtheneedfortheblockingcapacitors.Low-frequencyperformanceisthenlimitedonlybytheinputnetworkandspeakerresponse.CostandPCBspacearealsominimizedbyeliminatingthebulkycouplingcapacitor.
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APPLICATIONINFORMATION(continued)
VDD
-3 dB
VO(PP)CCRLVO(PP)
fc
Figure24.Single-EndedConfigurationandFrequencyResponse
Increasingpowertotheloaddoescarryapenaltyofincreasedinternalpowerdissipation.TheincreaseddissipationisunderstandableconsideringthattheBTLconfigurationproduces4×theoutputpowerofaSEconfiguration.Internaldissipationversusoutputpowerisdiscussedfurtherinthethermalconsiderationssection.
BTLAMPLIFIEREFFICIENCY
Linearamplifiersareinefficient.Theprimarycauseoftheseinefficienciesisvoltagedropacrosstheoutputstagetransistors.Therearetwocomponentsoftheinternalvoltagedrop.Oneistheheadroomordcvoltagedropthatvariesinverselytooutputpower.Thesecondcomponentisduetothesine-wavenatureoftheoutput.ThetotalvoltagedropcanbecalculatedbysubtractingtheRMSvalueoftheoutputvoltagefromVDD.TheinternalvoltagedropmultipliedbytheRMSvalueofthesupplycurrent,IDD(RMS),determinestheinternalpowerdissipationoftheamplifier.
Aneasy-to-useequationtocalculateefficiencystartsoutasbeingequaltotheratioofpowerfromthepowersupplytothepowerdeliveredtotheload.ToaccuratelycalculatetheRMSvaluesofpowerintheloadandintheamplifier,thecurrentandvoltagewaveformshapesmustfirstbeunderstood(seeFigure25).VOIDDVL(RMS)
IDD(RMS)
Figure25.VoltageandCurrentWaveformsforBTLAmplifiers
AlthoughthevoltagesandcurrentsforSEandBTLaresinusoidalintheload,currentsfromthesupplyaredifferentbetweenSEandBTLconfigurations.InanSEapplicationthecurrentwaveformisahalf-waverectifiedshape,whereasinBTLitisafull-waverectifiedwaveform.ThismeansRMSconversionfactorsaredifferent.Keepinmindthatformostofthewaveformboththepushandpulltransistorsarenotonatthesametime,whichsupportsthefactthateachamplifierintheBTLdeviceonlydrawscurrentfromthesupplyforhalfthewaveform.Thefollowingequationsarethebasisforcalculatingamplifierefficiency.
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APPLICATIONINFORMATION(continued)
Efficiency+
where
PL+
PPLSUP
Vp2L
Vǒ
LRMSǓRL
2+
2R
VP
Vǒ+LRMSǓǸ2
PSUP+VDDIǒ+
DDRMSǓI
DDǒRMS
VDD2VPpRL
(3)
Ǔ+
2VPpRL
pVP
EfficiencyofaBTLconfiguration++
2VDD
PLRLp
2ǒǓ2VDD
1ń2
(4)
Table1employsEquation4tocalculateefficienciesforthreedifferentoutputpowerlevels.Theefficiencyoftheamplifierisquitelowforlowerpowerlevelsandrisessharplyaspowertotheloadisincreasedresultinginanearlyflatinternalpowerdissipationoverthenormaloperatingrange.Theinternaldissipationatfulloutputpowerislessthaninthehalf-powerrange.Calculatingtheefficiencyforaspecificsystemisthekeytoproperpowersupplydesign.
Table1.EfficiencyvsOutputPowerin3.3-V8-ΩBTLSystems
OUTPUTPOWER(W)0.1250.250.375(1)
EFFICIENCY(%)33.647.658.3PEAK-to-PEAKVOLTAGE(V)1.412.002.45(1)INTERNALDISSIPATION(W)0.260.290.28High-peakvoltagevaluescausetheTHDtoincrease.
Afinalpointtorememberaboutlinearamplifiers(eitherSEorBTL)ishowtomanipulatethetermsintheefficiencyequationtoutmostadvantagewhenpossible.NotethatinEquation4,VDDisinthedenominator.ThisindicatesthatasVDDgoesdown,efficiencygoesup.
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APPLICATIONSCHEMATICS
Figure26isaschematicdiagramofatypicalhandheldaudioapplicationcircuit,configuredforagainof–10V/V.
CF5 pFAudio InputRF50 kΩVDD/24IN-IN+VDD6CS1 µFVDD
-+VO+5CIRI0.47 µF10 kΩ32CB2.2 µFBYPASS-+VO-87350 mWGNDFrom System Control1SHUTDOWNBiasControlFigure26.TPA321ApplicationCircuit
Figure27isaschematicdiagramofatypicalhandheldaudioapplicationcircuit,configuredforagainof–10V/Vwithadifferentialinput.
RF50 kΩAudio Input-RI10 kΩCIAudio Input+RI10 kΩVDD6VDD/243IN-IN+VO+5CS1 µFVDD
-+RF50 kΩ2BYPASS-+GND1SHUTDOWNBiasControlVO-87700 mWCICB2.2 µFFrom System ControlFigure27.TPA321ApplicationCircuitWithDifferentialInput
ItisimportanttonotethatusingtheadditionalRFresistorconnectedbetweenIN+andBYPASScausesVDD/2toshiftslightly,whichcouldinfluencetheTHD+Nperformanceoftheamplifier.AlthoughanadditionalexternaloperationalamplifiercouldbeusedtobufferBYPASSfromRF,testsinthelabhaveshownthattheTHD+NperformanceisonlyminimallyaffectedbyoperatinginthefullydifferentialmodeasshowninFigure27.ThefollowingsectionsdiscusstheselectionofthecomponentsusedinFigure26andFigure27.16
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COMPONENTSELECTION
GainSettingResistors,RFandRI
ThegainforeachaudioinputoftheTPA321issetbyresistorsRFandRIaccordingtoEquation5forBTLmode.
FBTLGain+AV+*2RI
ǒǓR
(5)
BTLmodeoperationbringsaboutthefactor2inthegainequationduetotheinvertingamplifiermirroringthevoltageswingacrosstheload.GiventhattheTPA321isaMOSamplifier,theinputimpedanceishigh;consequently,inputleakagecurrentsarenotgenerallyaconcern,althoughnoiseinthecircuitincreasesasthevalueofRFincreases.Inaddition,acertainrangeofRFvaluesisrequiredforproperstart-upoperationoftheamplifier.Takentogether,itisrecommendedthattheeffectiveimpedanceseenbytheinvertingnodeoftheamplifierbesetbetween5kΩand20kΩ.TheeffectiveimpedanceiscalculatedinEquation6.
RRFIEffectiveImpedance+
R)RFI(6)Asanexample,consideraninputresistanceof10kΩandafeedbackresistorof50kΩ.TheBTLgainofthe
amplifierwouldbe–10V/V,andtheeffectiveimpedanceattheinvertingterminalwouldbe8.3kΩ,whichiswellwithintherecommendedrange.
Forhigh-performanceapplicationsmetalfilmresistorsarerecommendedbecausetheytendtohavelowernoiselevelsthancarbonresistors.ForvaluesofRFabove50kΩ,theamplifiertendstobecomeunstableduetoapoleformedfromRFandtheinherentinputcapacitanceoftheMOSinputstructure.Forthisreason,placeasmallcompensationcapacitor(CF)ofapproximately5pFinparallelwithRFwhenRFisgreaterthan50kΩ.Ineffect,thiscreatesalow-passfilternetworkwiththecutofffrequencydefinedinEquation7.
−3 dB
fc+
12pRC
FF
fc
(7)
Forexample,ifRFis100kΩandCFis5pFthenfcis318kHz,whichiswelloutsideofaudiorange.InputCapacitor,CI
Inthetypicalapplication,inputcapacitorCIisrequiredtoallowtheamplifiertobiastheinputsignaltotheproperdclevelforoptimumoperation.Inthiscase,CIandRIformahigh-passfilterwiththecornerfrequencydeterminedinEquation8.
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−3 dB
fc+
12pRC
II
fc
(8)
ThevalueofCIisimportanttoconsiderasitdirectlyaffectsthebass(low-frequency)performanceofthecircuit.ConsidertheexamplewhereRIis10kΩandthespecificationcallsforaflatbassresponsedownto40Hz.Equation8isreconfiguredasEquation9.
1C+
I2pRfc
I(9)Inthisexample,CIis0.40µF,soonewouldlikelychooseavalueintherangeof0.47µFto1µF.Afurther
considerationforthiscapacitoristheleakagepathfromtheinputsourcethroughtheinputnetwork(RI,CI)andthefeedbackresistor(RF)totheload.Thisleakagecurrentcreatesadcoffsetvoltageattheinputtotheamplifierthatreducesusefulheadroom,especiallyinhighgainapplications.Forthisreasonalow-leakagetantalumorceramiccapacitoristhebestchoice.Whenpolarizedcapacitorsareused,thepositivesideofthecapacitorshouldfacetheamplifierinputinmostapplications,asthedclevelthereisheldatVDD/2,whichislikelyhigherthanthesourcedclevel.Itisimportanttoconfirmthecapacitorpolarityintheapplication.PowerSupplyDecoupling,CS
TheTPA321isahigh-performanceCMOSaudioamplifierthatrequiresadequatepowersupplydecouplingtoensuretheoutputtotalharmonicdistortion(THD)isaslowaspossible.Powersupplydecouplingalsopreventsoscillationsforlongleadlengthsbetweentheamplifierandthespeaker.Theoptimumdecouplingisachievedbyusingtwocapacitorsofdifferenttypesthattargetdifferenttypesofnoiseonthepowersupplyleads.Forhigherfrequencytransients,spikes,ordigitalhashontheline,agoodlowequivalent-series-resistance(ESR)ceramiccapacitor,typically0.1µF,placedascloseaspossibletothedeviceVDDlead,worksbest.Forfilteringlower-frequencynoisesignals,alargeraluminumelectrolyticcapacitorof10µForgreaterplacedneartheaudiopoweramplifierisrecommended.MidrailBypassCapacitor,CB
Themidrailbypasscapacitor,CB,isthemostcriticalcapacitorandservesseveralimportantfunctions.Duringstart-uporrecoveryfromshutdownmode,CBdeterminestherateatwhichtheamplifierstartsup.Thesecondfunctionistoreducenoiseproducedbythepowersupplycausedbycouplingintotheoutputdrivesignal.Thisnoiseisfromthemidrailgenerationcircuitinternaltotheamplifier,whichappearsasdegradedPSRRandTHD+N.Thecapacitorisfedfroma250-kΩsourceinsidetheamplifier.Tokeepthestart-uppopaslowaspossible,therelationshipshowninEquation10shouldbemaintained,whichinsurestheinputcapacitorisfullychargedbeforethebypasscapacitorisfullychargedandtheamplifierstartsup.
101v
ǒCB 250kΩǓǒRF)RIǓCI
(10)
Asanexample,consideracircuitwhereCBis2.2µF,CIis0.47µF,RFis50kΩ,andRIis10kΩ.Insertingthese
valuesintotheEquation10weget:18.2≤35.5
whichsatisfiestherule.Bypasscapacitor,CB,valuesof2.2-µFto1-µFceramicortantalumlow-ESRcapacitorsarerecommendedforthebestTHDandnoiseperformance.
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TPA321
www.ti.com
SLOS312C–JUNE2000–REVISEDJUNE2004
USINGLOW-ESRCAPACITORS
Low-ESRcapacitorsarerecommendedthroughoutthisapplication.Areal(asopposedtoideal)capacitorcanbemodeledsimplyasaresistorinserieswithanidealcapacitor.Thevoltagedropacrossthisresistorminimizesthebeneficialeffectsofthecapacitorinthecircuit.Thelowertheequivalentvalueofthisresistance,themoretherealcapacitorbehaveslikeanidealcapacitor.
5-VVERSUS3.3-VOPERATION
TheTPA321operatesoverasupplyrangeof2.5Vto5.5V.Thisdatasheetprovidesfullspecificationsfor5-Vand3.3-Voperation,astheseareconsideredtobethetwomostcommonstandardvoltages.Therearenospecialconsiderationsfor3.3-Vversus5-Voperationwithrespecttosupplybypassing,gainsetting,orstability.Themostimportantconsiderationisthatofoutputpower.EachamplifierinTPA321canproduceamaximumvoltageswingofVDD–1V.Thismeans,for3.3-Voperation,clippingstartstooccurwhenVO(PP)=2.3VasopposedtoVO(PP)=4Vat5V.Thereducedvoltageswingsubsequentlyreducesmaximumoutputpowerintoan8-Ωloadbeforedistortionbecomessignificant.
Operationfrom3.3-Vsupplies,ascanbeshownfromtheefficiencyformulainEquation4,consumesapproximatelytwo-thirdsthesupplypowerforagivenoutput-powerlevelthanoperationfrom5-Vsupplies.
HEADROOMANDTHERMALCONSIDERATIONS
Linearpoweramplifiersdissipateasignificantamountofheatinthepackageundernormaloperatingconditions.AtypicalmusicCDrequires12dBto15dBofdynamicheadroomtopasstheloudestportionswithoutdistortionascomparedwiththeaveragepoweroutput.TheTPA321datasheetshowsthatwhentheTPA321isoperatingfroma5-Vsupplyintoa8-Ωspeaker,350mWpeaksareavailable.ConvertingwattstodB:
P
P+10LogW+10Log350mW+–4.6dBdBP1W
refSubtractingtheheadroomrestrictiontoobtaintheaveragelisteninglevelwithoutdistortionyields:
4.6dB–15dB=–19.6dB(15-dBheadroom)4.6dB–12dB=–16.6dB(12-dBheadroom)4.6dB–9dB=–13.6dB(9-dBheadroom)4.6dB–6dB=–10.6dB(6-dBheadroom)4.6dB–3dB=–7.6dB(3-dBheadroom)
ConvertingdBbackintowatts:
PW=10PdB/10×Pref
=11mW(15dBheadroom)=22mW(12-dBheadroom)=44mW(9-dBheadroom)=88mW(6-dBheadroom)=175mW(3-dBheadroom)
Thisisvaluableinformationtoconsiderwhenattemptingtoestimatetheheatdissipationrequirementsfortheamplifiersystem.Comparingtheabsoluteworstcase,whichis350mWofcontinuouspoweroutputwith0dBofheadroom,against12-dBand15-dBapplicationsdrasticallyaffectsmaximumambienttemperatureratingsforthesystem.Usingthepowerdissipationcurvesfora5-V,8-Ωsystem,theinternaldissipationintheTPA321andmaximumambienttemperaturesisshowninTable2.
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TPA321
SLOS312C–JUNE2000–REVISEDJUNE2004
www.ti.com
Table2.TPA321PowerRating,5-V,8-ΩBTL
PEAKOUTPUTPOWER(mW)350350350350350350AVERAGEOUTPUTPOWER350mW175mW(3dB)88mW(6dB)44mW(9dB)22mW(12dB)11mW(15dB)POWERDISSIPATION(mW)600500380300200180MAXIMUMAMBIENTTEMPERATURE0CFM46°C64°C85°C98°C115°C119°CTable2showsthattheTPA321canbeusedtoitsfull350-mWratingwithoutanyheatsinkinginstillairupto46°C.
20
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PACKAGEOPTIONADDENDUM
www.ti.com
18-Jul-2006
PACKAGINGINFORMATION
OrderableDevice
TPA321DTPA321DG4TPA321DGN
Status(1)ACTIVEACTIVEACTIVE
PackageTypeSOICSOICMSOP-Power PADMSOP-Power PADMSOP-Power PADMSOP-Power PADSOICSOIC
PackageDrawing
DDDGN
PinsPackageEcoPlan(2)
Qty888
757580
Green(RoHS&noSb/Br)Green(RoHS&noSb/Br)Green(RoHS&noSb/Br)Green(RoHS&noSb/Br)
Lead/BallFinishCUNIPDAUCUNIPDAUCUNIPDAU
MSLPeakTemp(3)Level-1-260C-UNLIMLevel-1-260C-UNLIMLevel-1-260C-UNLIM
TPA321DGNG4ACTIVEDGN880CUNIPDAULevel-1-260C-UNLIM
TPA321DGNRACTIVEDGN8
2500Green(RoHS&
noSb/Br)2500Green(RoHS&
noSb/Br)2500Green(RoHS&
noSb/Br)2500Green(RoHS&
noSb/Br)
CUNIPDAULevel-1-260C-UNLIM
TPA321DGNRG4ACTIVEDGN8CUNIPDAULevel-1-260C-UNLIM
TPA321DRTPA321DRG4
(1)
ACTIVEACTIVE
DD
88
CUNIPDAUCUNIPDAU
Level-1-260C-UNLIMLevel-1-260C-UNLIM
Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.Samplesmayormaynotbeavailable.OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)
EcoPlan-Theplannedeco-friendlyclassification:Pb-Free(RoHS),Pb-Free(RoHSExempt),orGreen(RoHS&noSb/Br)-pleasecheckhttp://www.ti.com/productcontentforthelatestavailabilityinformationandadditionalproductcontentdetails.TBD:ThePb-Free/Greenconversionplanhasnotbeendefined.
Pb-Free(RoHS):TI'sterms\"Lead-Free\"or\"Pb-Free\"meansemiconductorproductsthatarecompatiblewiththecurrentRoHSrequirementsforall6substances,includingtherequirementthatleadnotexceed0.1%byweightinhomogeneousmaterials.Wheredesignedtobesolderedathightemperatures,TIPb-Freeproductsaresuitableforuseinspecifiedlead-freeprocesses.
Pb-Free(RoHSExempt):ThiscomponenthasaRoHSexemptionforeither1)lead-basedflip-chipsolderbumpsusedbetweenthedieandpackage,or2)lead-baseddieadhesiveusedbetweenthedieandleadframe.ThecomponentisotherwiseconsideredPb-Free(RoHScompatible)asdefinedabove.
Green(RoHS&noSb/Br):TIdefines\"Green\"tomeanPb-Free(RoHScompatible),andfreeofBromine(Br)andAntimony(Sb)basedflameretardants(BrorSbdonotexceed0.1%byweightinhomogeneousmaterial)
(3)
MSL,PeakTemp.--TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.Effortsareunderwaytobetterintegrateinformationfromthirdparties.TIhastakenandcontinuestotakereasonablestepstoproviderepresentativeandaccurateinformationbutmaynothaveconducteddestructivetestingorchemicalanalysisonincomingmaterialsandchemicals.TIandTIsuppliersconsidercertaininformationtobeproprietary,andthusCASnumbersandotherlimitedinformationmaynotbeavailableforrelease.
InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
Addendum-Page1
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PACKAGEMATERIALSINFORMATION
www.ti.com
14-Jul-2012
TAPEANDREELINFORMATION
*Alldimensionsarenominal
Device
PackagePackagePinsTypeDrawingMSOP-Power PADSOIC
DGN
8
SPQ
ReelReelA0DiameterWidth(mm)(mm)W1(mm)330.0
12.4
5.3
B0(mm)3.4
K0(mm)1.4
P1(mm)8.0
WPin1(mm)Quadrant12.0
Q1
TPA321DGNR2500
TPA321DRD82500330.012.46.45.22.18.012.0Q1
PackMaterials-Page1
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PACKAGEMATERIALSINFORMATION
www.ti.com
14-Jul-2012
*Alldimensionsarenominal
DeviceTPA321DGNRTPA321DR
PackageTypeMSOP-PowerPAD
SOIC
PackageDrawing
DGND
Pins88
SPQ25002500
Length(mm)
358.0367.0
Width(mm)335.0367.0
Height(mm)
35.035.0
PackMaterials-Page2
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