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LM4755www.
ti.
comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013LM4755Stereo11WAudioPowerAmplifierwithMuteCheckforSamples:LM47551FEATURESDESCRIPTIONTheLM4755isastereoaudioamplifiercapableof2Drives4and8Loadsdelivering11WperchannelofcontinuousaverageIntegratedMuteFunctionoutputpowertoa4loador7Wperchannelinto8InternalGainResistorsusingasingle24Vsupplyat10%THD+N.
Theinternalmutecircuitandpre-setgainresistorsprovideMinimalExternalComponentsNeededforaveryeconomicaldesignsolution.
SingleSupplyOperationOutputpowerspecificationsatboth20Vand24VInternalCurrentLimitingandThermalsuppliesandlowexternalcomponentcountofferhighProtectionvaluetoconsumerelectronicmanufacturersforCompact9-leadTO-220PackagestereoTVandcompactstereoapplications.
TheWideSupplyRange9V-40VLM4755isspecificallydesignedforsinglesupplyoperation.
APPLICATIONSStereosTVsCompactStereosMiniComponentStereosKEYSPECIFICATIONSOutputPowerat10%THDwith1kHzinto4atVCC=24V11W(typ)OutputPowerat10%THDwith1kHzinto8atVCC=24V7W(typ)ClosedLoopGain34dB(typ)POat10%THD+N@1kHzinto4Single-EndedDDPAKPackageatVCC=12V2.
5W(typ)POat10%THD+N@1kHzinto8BridgedDDPAKPackageatVCC=12V5W(typ)1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
2Alltrademarksarethepropertyoftheirrespectiveowners.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright1999–2013,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALAPPLICATIONFigure1.
TypicalAudioAmplifierApplicationCircuitConnectionDiagram9PinTO-220PlasticPackage(TopView)SeePackageNumberNEC9PinDDPAKPlasticPackage(TopView)SeePackageNumberKTW2SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013Thesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
ABSOLUTEMAXIMUMRATINGS(1)(2)(3)(4)SupplyVoltage40VInputVoltage±0.
7VInputVoltageatOutputPins(5)GND-0.
4VOutputCurrentInternallyLimitedPowerDissipation(6)62.
5WESDSusceptibility(7)2kVJunctionTemperature150°CSolderingInformationNECPackage(10seconds)250°CStorageTemperature40°Cto150°C(1)AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.
OperatingRatingsindicateconditionsforwhichthedeviceisfunctional,butdonotensurespecificperformancelimits.
ElectricalCharacteristicsstateDCandACelectricalspecificationsunderparticulartestconditionswhichensurespecificperformancelimits.
ThisassumesthatthedeviceiswithintheOperatingRatings.
Specificationsarenotensuredforparameterswherenolimitisgiven,however,thetypicalvalueisagoodindicationofdeviceperformance.
(2)IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexasInstrumentsSalesOffice/Distributorsforavailabilityandspecifications.
(3)TheTO-263PackageisnotrecommendedforVS>16Vduetoimpracticalheatsinkinglimitations.
(4)AllvoltagesaremeasuredwithrespecttotheGNDpin(5),unlessotherwsespecified.
(5)TheoutputsoftheLM4755cannotbedrivenexternallyinanymodewithavoltagelowerthan-0.
4VbelowGNDorpermanentdamagetotheLM4755willresult.
(6)Foroperatingatcasetemperaturesabove25°C,thedevicemustbederatedbasedona150°CmaximumjunctiontemperatureandathermalresistanceofθJC=2°C/W(junctiontocase).
RefertothesectionDETERMININGMAXIMUMPOWERDISSIPATIONintheAPPLICATIONINFORMATIONsectionformoreinformation.
(7)Humanbodymodel,100pFdischargedthrougha1.
5kresistor.
OPERATINGRATINGSTemperatureRangeTMIN≤TA≤TMAX40°C≤TA≤+85°CSupplyVoltage9Vto32VθJC2°C/WθJA76°C/WELECTRICALCHARACTERISTICSThefollowingspecificationsapplytoeachchannelwithVCC=24V,TA=25°Cunlessotherwisespecified.
LM4755UnitsSymbolParameterConditions(Limits)Typical(1)LimitITOTALTotalQuiescentPowerMuteOff1015mA(max)SupplyCurrent7mA(min)MuteOn7mAPOOutputPower(Continuousf=1kHz,THD+N=10%,RL=87WAverageperChannel)f=1kHz,THD+N=10%,RL=41110W(min)VS=20V,RL=84WVS=20V,RL=47Wf=1kHz,THD+N=10%,RL=42.
5WVS=12V,DDPAKPkg.
THDTotalHarmonicDistortionf=1kHz,PO=1W/ch,RL=80.
08%VOSWOutputSwingPO=10W,RL=815VPO=10W,RL=414VXTALKChannelSeparationSeeApps.
Circuit(Figure1)55dBf=1kHz,VO=4Vrms(1)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback3ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comELECTRICALCHARACTERISTICS(continued)ThefollowingspecificationsapplytoeachchannelwithVCC=24V,TA=25°Cunlessotherwisespecified.
LM4755UnitsSymbolParameterConditions(Limits)Typical(1)LimitPSRRPowerSupplyRejectionRatioSeeApps.
Circuit(Figure1)50dBf=120Hz,VO=1mVrmsVODVDifferentialDCOutputOffsetVIN=0V0.
090.
4V(max)VoltageSRSlewRate2V/sRINInputImpedance83kPBWPowerBandwidth3dBBWatPO=2.
5W,RL=865kHzAVCLClosedLoopGain(InternallySet)RL=83433dB(min)35dB(max)εINNoiseIHF-AWeightingFilter,RL=80.
2mVrmsOutputReferredIOOutputShortCircuitLimitVIN=0.
5V,RL=22A(min)MutePinMuteLowInputVoltageNotinMuteMode0.
8V(max)VILVIHMuteHighInputVoltageInMuteMode2.
02.
5V(min)AMMuteAttenuationVMUTE=5.
0V80dBEQUIVALENTSCHEMATICFigure2.
4SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TESTCIRCUITFigure3.
TestCircuitCopyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback5ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comSYSTEMAPPLICATIONCIRCUITFigure4.
CircuitforExternalComponentsDescriptionEXTERNALCOMPONENTSDESCRIPTIONComponentsFunctionDescription1,2CSProvidespowersupplyfilteringandbypassing.
3,4RSNWorkswithCSNtostabilizetheoutputstagefromhighfrequencyoscillations.
5,6CSNWorkswithRSNtostabilizetheoutputstagefromhighfrequencyoscillations.
7CbProvidesfilteringfortheinternallygeneratedhalf-supplybiasgenerator.
8,9CiInputACcouplingcapacitorwhichblocksDCvoltageattheamplifier'sinputterminals.
Alsocreatesahighpassfilterwithfc=1/(2πRinCin).
10,11CoOutputACcouplingcapacitorwhichblocksDCvoltageattheamplifier'soutputterminal.
Createsahighpassfilterwithfc=1/(2πRoutCout).
12,13RiVoltagecontrol-limitsthevoltagelevelallowedtotheamplifier'sinputterminals.
14RmWorkswithCmtoprovidemutefunctiontiming.
15CmWorkswithRmtoprovidemutefunctiontiming.
6SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICSTypicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure5.
Figure6.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure7.
Figure8.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure9.
Figure10.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback7ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure11.
Figure12.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure13.
Figure14.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure15.
Figure16.
8SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure17.
Figure18.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure19.
Figure20.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure21.
Figure22.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback9ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure23.
Figure24.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure25.
Figure26.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure27.
Figure28.
10SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
OutputPowervsSupplyVoltageOutputPowervsSupplyVoltageFigure29.
Figure30.
FrequencyResponseTHD+NvsFrequencyFigure31.
Figure32.
THD+NvsFrequencyFrequencyResponseFigure33.
Figure34.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
ChannelSeparationPSRRvsFrequencyFigure35.
Figure36.
SupplyCurrentvsSupplyVoltagePowerDeratingCurveFigure37.
Figure38.
PowerDissipationvsOutputPowerPowerDissipationvsOutputPowerFigure39.
Figure40.
12SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
PowerDissipationvsOutputPowerPowerDissipationvsOutputPowerFigure41.
Figure42.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback13ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comAPPLICATIONINFORMATIONTheLM4755containscircuitrytopulldownthebiaslineinternally,effectivelyshuttingdowntheinputstage.
AnexternalR-Cshouldbeusedtoadjustthetimingofthepull-down.
Ifthebiaslineispulleddowntooquickly,currentsinducedintheinternalbiasresistorswillcauseamomentaryDCvoltagetoappearacrosstheinputsofeachamplifier'sinternaldifferentialpair,resultinginanoutputDCshifttowardsVsupply.
AnR-Ctimingcircuitshouldbeusedtolimitthepull-downtimesuchthatoutput"pops"andsignalfeedthroughswillbeminimized.
Thepull-downtimingisafunctionofanumberoffactors,includingtheinternalmutecircuitry,thevoltageusedtoactivatethemute,thebiascapacitor,thehalf-supplyvoltage,andinternalresistancesusedinthehalf-supplygenerator.
Table1showsalistofrecommendedvaluesfortheexternalR-C.
Table1.
RECOMMENDEDVALUESFORMUTECIRCUITVMUTEVCCRmCm5V12V18k10F5V15V18k10F5V20V12k10F5V24V12k10F5V28V8.
2k10F5V30V8.
2k10FCAPACITORSELECTIONANDFREQUENCYRESPONSEWiththeLM4755,asinallsinglesupplyamplifiers,ACcouplingcapacitorsareusedtoisolatetheDCvoltagepresentattheinputs(pins3,7)andoutputs(pins1,8).
AsmentionedearlierintheEXTERNALCOMPONENTSDESCRIPTIONsectionthesecapacitorscreatehigh-passfilterswiththeircorrespondinginput/outputimpedances.
TheTypicalApplicationCircuitshowninFigure1showsinputandoutputcapacitorsof0.
1Fand1,000Frespectively.
Attheinput,withan83ktypicalinputresistance,theresultisahighpass3dBpointoccurringat19Hz.
Thereisanotherhighpassfilterat39.
8Hzcreatedwiththeoutputloadresistanceof4.
Carefulselectionofthesecomponentsisnecessarytoensurethatthedesiredfrequencyresponseisobtained.
TheFrequencyResponsecurvesintheTYPICALPERFORMANCECHARACTERISTICSsectionshowhowdifferentoutputcouplingcapacitorsaffectthelowfrequencyroll-off.
OPERATINGINBRIDGE-MODEThoughdesignedforuseasasingle-endedamplifier,theLM4755canbeusedtodrivealoaddifferentially(bridge-mode).
Duetothelowpincountofthepackage,onlythenon-invertinginputsareavailable.
Aninvertedsignalmustbeprovidedtooneoftheinputs.
Thiscaneasilybedonewiththeuseofaninexpensiveop-ampconfiguredasastandardinvertingamplifier.
AnLF353isagoodlow-costchoice.
Caremustbetaken,however,forabridge-modeamplifiermusttheoreticallydissipatefourtimesthepowerofasingle-endedtype.
Theloadseenbyeachamplifieriseffectivelyhalfthatoftheactualloadbeingused,thusanamplifierdesignedtodrivea4loadinsingle-endedmodeshoulddrivean8loadwhenoperatinginbridge-mode.
14SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013Figure43.
Bridge-ModeApplicationFigure44.
THD+NvsPOUTforBridge-ModeApplicationCopyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback15ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comPREVENTINGOSCILLATIONSWiththeintegrationofthefeedbackandbiasresistorson-chip,theLM4755fitsintoaverycompactpackage.
However,duetothecloseproximityofthenon-invertinginputpinstothecorrespondingoutputpins,theinputsshouldbeACterminatedatalltimes.
Iftheinputsareleftfloating,theamplifierwillhaveapositivefeedbackpaththroughhighimpedancecoupling,resultinginahighfrequencyoscillation.
Inmostapplications,thisterminationistypicallyprovidedbythepreviousstage'ssourceimpedance.
Iftheapplicationwillrequireanexternalsignal,theinputsshouldbeterminatedtogroundwitharesistanceof50korlessontheACsideoftheinputcouplingcapacitors.
UNDERVOLTAGESHUTDOWNIfthepowersupplyvoltagedropsbelowtheminimumoperatingsupplyvoltage,theinternalunder-voltagedetectioncircuitrypullsdownthehalf-supplybiasline,shuttingdownthepreampsectionoftheLM4755.
DuetothewideoperatingsupplyrangeoftheLM4755,thethresholdissettojustunder9V.
Theremaybecertainapplicationswhereahigherthresholdvoltageisdesired.
Oneexampleisadesignrequiringahighoperatingsupplyvoltage,withlargesupplyandbiascapacitors,andthereislittleornoothercircuitryconnectedtothemainpowersupplyrail.
Inthiscircuit,whenthepowerisdisconnected,thesupplyandbiascapacitorswilldischargeataslowerrate,possiblyresultinginaudibleoutputdistortionasthedecayingvoltagebeginstocliptheoutputsignal.
Anexternalcircuitmaybeusedtosenseforthedesiredthreshold,andpullthebiasline(pin6)togroundtodisabletheinputpreamp.
Figure45showsanexampleofsuchacircuit.
Whenthevoltageacrossthezenerdiodedropsbelowitsthreshold,currentflowintothebaseofQ1isinterrupted.
Q2thenturnson,dischargingthebiascapacitor.
Thisdischargerateisgovernedbyseveralfactors,includingthebiascapacitorvalue,thebiasvoltage,andtheresistorattheemitterofQ2.
Anequationforapproximatingthevalueoftheemitterdischargeresistor,R,isgivenbelow:R=(0.
7v)/(Cb(VCC/2)/0.
1s)(1)Notethatthisisonlyalinearizedapproximationbasedonadischargetimeof0.
1s.
Thecircuitshouldbeevaluatedandadjustedforeachapplication.
AsmentionedearlierintheBuilt-inMuteCircuitsection,whenusinganexternalcircuittopulldownthebiasline,therateofdischargewillhaveaneffectontheturn-offinduceddistortions.
PleaserefertotheTable1sectionformoreinformation.
Figure45.
ExternalUndervoltagePull-DownTHERMALCONSIDERATIONSHeatSinkingProperheatsinkingisnecessarytoensurethattheamplifierwillfunctioncorrectlyunderalloperatingconditions.
Aheatsinkthatistoosmallwillcausethedietoheatexcessivelyandwillresultinadegradedoutputsignalasthethermalprotectioncircuitrybeginstooperate.
16SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013Thechoiceofaheatsinkforagivenapplicationisdictatedbyseveralfactors:themaximumpowertheICneedstodissipate,theworst-caseambienttemperatureofthecircuit,thejunction-to-casethermalresistance,andthemaximumjunctiontemperatureoftheIC.
Theheatflowapproximationequationusedindeterminingthecorrectheatsinkmaximumthermalresistanceisgivenbelow:TJ–TA=PDMAX(θJC+θCS+θSA)wherePDMAX=maximumpowerdissipationoftheICTJ(°C)=junctiontemperatureoftheICTA(°C)=ambienttemperatureθJC(°C/W)=junction-to-casethermalresistanceoftheICθCS(°C/W)=case-to-heatsinkthermalresistance(typically0.
2to0.
5°C/W)θSA(°C/W)=thermalresistanceofheatsink(2)Whendeterminingtheproperheatsink,theaboveequationshouldbere-writtenas:θSA≤[(TJ–TA)/PDMAX]-θJC–θCS(3)DDPAKHEATSINKINGSurfacemountapplicationswillbelimitedbythethermaldissipationpropertiesofprintedcircuitboardarea.
TheDDPAKpackageisnotrecommendedforsurfacemountapplicationswithVS>16Vduetolimitedprintedcircuitboardarea.
ThereareDDPAKpackageenhancements,suchasclip-onheatsinksandheatsinkswithadhesives,thatcanbeusedtoimproveperformance.
StandardFR-4single-sidedcoppercladwillhaveanapproximateThermalresistance(θSA)rangingfrom:1.
5*1.
5in.
sq.
20–27°C/W(TA=28°C,Sinewavetesting,1oz.
Copper)2*2in.
sq.
16–23°C/WTheabovevaluesforθSAvarywidelyduetodimensionalproportions(i.
e.
variationsinwidthandlengthwillvaryθSA).
Foraudioapplications,wherepeakpowerlevelsareshortinduration,thispartwillperformsatisfactorywithlessheatsinking/coppercladarea.
Aswithanyhighpowerdesignproperbenchtestingshouldbeundertakentoassurethedesigncandissipatetherequiredpower.
Properbenchtestingrequiresattentiontoworstcaseambienttemperatureandairflow.
Athighpowerdissipationlevelsthepartwillshowatendencytoincreasesaturationvoltages,thuslimitingtheundistortedpowerlevels.
DETERMININGMAXIMUMPOWERDISSIPATIONForasingle-endedclassABpoweramplifier,thetheoreticalmaximumpowerdissipationpointisafunctionofthesupplyvoltage,VS,andtheloadresistance,RLandisgivenbythefollowingequation:(singlechannel)PDMAX(W)=[VS2/(2π2RL)]Theaboveequationisforasinglechannelclass-ABpoweramplifier.
FordualamplifierssuchastheLM4755,theequationforcalculatingthetotalmaximumpowerdissipatedis:(dualchannel)PDMAX(W)=2[VS2/(2π2RL)]orVS2/(π2RL)(BridgedOutputs)PDMAX(W)=4[VS2/(2π2RL)]Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback17ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comHEATSINKDESIGNEXAMPLEDeterminethesystemparameters:VS=24VOperatingSupplyVoltageRL=4MinimumLoadImpedanceTA=55°CWorstCaseAmbientTemperatureDeviceparametersfromthedatasheet:TJ=150°CMaximumJunctionTemperatureθJC=2°C/WJunction-to-CaseThermalResistanceCalculations:2PDMAX=2[VS2/2π2RL)]=(24V)2/(2π24)=14.
6WθSA≤[(TJ-TA)/PDMAX]-θJC–θCS=[(150°C-55°C)/14.
6W]-2°C/W–0.
2°C/W=4.
3°C/WConclusion:ChooseaheatsinkwithθSA≤4.
3°C/W.
DDPAKHEATSINKDESIGNEXAMPLESExample1:(StereoSingle-EndedOutput)Given:TA=30°CTJ=150°CRL=4VS=12VθJC=2°C/WPDMAXfromPDvsPOGraph:PDMAX≈3.
7W(4)CalculatingPDMAX:PDMAX=VCC2/(π2RL)=(12V)2/π2(4))=3.
65W(5)CalculatingHeatsinkThermalResistance:θSA7W2.
0°C/W0.
2°C/W=30.
2°C/W(7)Thereforetherecommendationistouse1.
5*1.
5squareinchofsingle-sidedcopperclad.
Example2:(StereoSingle-EndedOutput)Given:TA=50°CTJ=150°CRL=4VS=12VθJC=2°C/WPDMAXfromPDvsPOGraph:PDMAX≈3.
7W(8)CalculatingPDMAX:PDMAX=VCC2/(π2RL)=(12V)2/(π2(4))=3.
65W(9)CalculatingHeatsinkThermalResistance:θSA<[(TJTA)/PDMAX]θJCθCS(10)18SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013θSA<100°C/3.
7W2.
0°C/W0.
2°C/W=24.
8°C/W(11)Thereforetherecommendationistouse2.
0*2.
0squareinchofsingle-sidedcopperclad.
Example3:(BridgedOutput)Given:TA=50°CTJ=150°CRL=8VS=12VθJC=2°C/WCalculatingPDMAX:PDMAX=4[VCC2/(2π2RL)]=4(12V)2/(2π2(8))=3.
65W(12)CalculatingHeatsinkThermalResistance:θSA<[(TJTA)/PDMAX]θJCθCS(13)θSA<100°C/3.
7W2.
0°C/W0.
2°C/W=24.
8°C/W(14)Thereforetherecommendationistouse2.
0*2.
0squareinchofsingle-sidedcopperclad.
LAYOUTANDGROUNDRETURNSProperPCboardlayoutisessentialforgoodcircuitperformance.
WhenlayingoutaPCboardforanaudiopoweramplifier,particularattentionmustbepaidtotheroutingoftheoutputsignalgroundreturnsrelativetotheinputsignalandbiascapacitorgrounds.
Topreventanygroundloops,thegroundreturnsfortheoutputsignalsshouldberoutedseparatelyandbroughttogetheratthesupplyground.
Theinputsignalgroundsandthebiascapacitorgroundlineshouldalsoberoutedseparately.
The0.
1FhighfrequencysupplybypasscapacitorshouldbeplacedascloseaspossibletotheIC.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback19ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comPCBOARDLAYOUT-COMPOSITEFigure46.
20SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013PCBOARDLAYOUT-SILKSCREENFigure47.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback21ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comPCBOARDLAYOUT-SOLDERSIDEFigure48.
22SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013REVISIONHISTORYChangesfromRevisionD(April2013)toRevisionEPageChangedlayoutofNationalDataSheettoTIformat22Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback23ProductFolderLinks:LM4755PACKAGEOPTIONADDENDUMwww.
ti.
com10-Dec-2020Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Leadfinish/Ballmaterial(6)MSLPeakTemp(3)OpTemp(°C)DeviceMarking(4/5)SamplesLM4755TSX/NOPBACTIVEDDPAK/TO-263KTW9500RoHS-Exempt&GreenSNLevel-3-245C-168HR-20to80LM4755TS(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)RoHS:TIdefines"RoHS"tomeansemiconductorproductsthatarecompliantwiththecurrentEURoHSrequirementsforall10RoHSsubstances,includingtherequirementthatRoHSsubstancedonotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,"RoHS"productsaresuitableforuseinspecifiedlead-freeprocesses.
TImayreferencethesetypesofproductsas"Pb-Free".
RoHSExempt:TIdefines"RoHSExempt"tomeanproductsthatcontainleadbutarecompliantwithEURoHSpursuanttoaspecificEURoHSexemption.
Green:TIdefines"Green"tomeanthecontentofChlorine(Cl)andBromine(Br)basedflameretardantsmeetJS709Blowhalogenrequirementsof<=1000ppmthreshold.
Antimonytrioxidebasedflameretardantsmustalsomeetthe<=1000ppmthresholdrequirement.
(3)MSL,PeakTemp.
-TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)Theremaybeadditionalmarking,whichrelatestothelogo,thelottracecodeinformation,ortheenvironmentalcategoryonthedevice.
(5)MultipleDeviceMarkingswillbeinsideparentheses.
OnlyoneDeviceMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireDeviceMarkingforthatdevice.
(6)Leadfinish/Ballmaterial-OrderableDevicesmayhavemultiplematerialfinishoptions.
Finishoptionsareseparatedbyaverticalruledline.
Leadfinish/Ballmaterialvaluesmaywraptotwolinesifthefinishvalueexceedsthemaximumcolumnwidth.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.
TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
Effortsareunderwaytobetterintegrateinformationfromthirdparties.
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TAPEANDREELINFORMATION*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQReelDiameter(mm)ReelWidthW1(mm)A0(mm)B0(mm)K0(mm)P1(mm)W(mm)Pin1QuadrantLM4755TSX/NOPBDDPAK/TO-263KTW9500330.
024.
410.
7514.
855.
016.
024.
0Q2PACKAGEMATERIALSINFORMATIONwww.
ti.
com8-Nov-2013PackMaterials-Page1*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQLength(mm)Width(mm)Height(mm)LM4755TSX/NOPBDDPAK/TO-263KTW9500367.
0367.
045.
0PACKAGEMATERIALSINFORMATIONwww.
ti.
com8-Nov-2013PackMaterials-Page2MECHANICALDATAKTW0009Awww.
ti.
comBOTTOMSIDEOFPACKAGETS9A(RevB)IMPORTANTNOTICEANDDISCLAIMERTIPROVIDESTECHNICALANDRELIABILITYDATA(INCLUDINGDATASHEETS),DESIGNRESOURCES(INCLUDINGREFERENCEDESIGNS),APPLICATIONOROTHERDESIGNADVICE,WEBTOOLS,SAFETYINFORMATION,ANDOTHERRESOURCES"ASIS"ANDWITHALLFAULTS,ANDDISCLAIMSALLWARRANTIES,EXPRESSANDIMPLIED,INCLUDINGWITHOUTLIMITATIONANYIMPLIEDWARRANTIESOFMERCHANTABILITY,FITNESSFORAPARTICULARPURPOSEORNON-INFRINGEMENTOFTHIRDPARTYINTELLECTUALPROPERTYRIGHTS.
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MailingAddress:TexasInstruments,PostOfficeBox655303,Dallas,Texas75265Copyright2020,TexasInstrumentsIncorporated
ti.
comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013LM4755Stereo11WAudioPowerAmplifierwithMuteCheckforSamples:LM47551FEATURESDESCRIPTIONTheLM4755isastereoaudioamplifiercapableof2Drives4and8Loadsdelivering11WperchannelofcontinuousaverageIntegratedMuteFunctionoutputpowertoa4loador7Wperchannelinto8InternalGainResistorsusingasingle24Vsupplyat10%THD+N.
Theinternalmutecircuitandpre-setgainresistorsprovideMinimalExternalComponentsNeededforaveryeconomicaldesignsolution.
SingleSupplyOperationOutputpowerspecificationsatboth20Vand24VInternalCurrentLimitingandThermalsuppliesandlowexternalcomponentcountofferhighProtectionvaluetoconsumerelectronicmanufacturersforCompact9-leadTO-220PackagestereoTVandcompactstereoapplications.
TheWideSupplyRange9V-40VLM4755isspecificallydesignedforsinglesupplyoperation.
APPLICATIONSStereosTVsCompactStereosMiniComponentStereosKEYSPECIFICATIONSOutputPowerat10%THDwith1kHzinto4atVCC=24V11W(typ)OutputPowerat10%THDwith1kHzinto8atVCC=24V7W(typ)ClosedLoopGain34dB(typ)POat10%THD+N@1kHzinto4Single-EndedDDPAKPackageatVCC=12V2.
5W(typ)POat10%THD+N@1kHzinto8BridgedDDPAKPackageatVCC=12V5W(typ)1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
2Alltrademarksarethepropertyoftheirrespectiveowners.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright1999–2013,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALAPPLICATIONFigure1.
TypicalAudioAmplifierApplicationCircuitConnectionDiagram9PinTO-220PlasticPackage(TopView)SeePackageNumberNEC9PinDDPAKPlasticPackage(TopView)SeePackageNumberKTW2SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
ti.
comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013Thesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
ABSOLUTEMAXIMUMRATINGS(1)(2)(3)(4)SupplyVoltage40VInputVoltage±0.
7VInputVoltageatOutputPins(5)GND-0.
4VOutputCurrentInternallyLimitedPowerDissipation(6)62.
5WESDSusceptibility(7)2kVJunctionTemperature150°CSolderingInformationNECPackage(10seconds)250°CStorageTemperature40°Cto150°C(1)AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.
OperatingRatingsindicateconditionsforwhichthedeviceisfunctional,butdonotensurespecificperformancelimits.
ElectricalCharacteristicsstateDCandACelectricalspecificationsunderparticulartestconditionswhichensurespecificperformancelimits.
ThisassumesthatthedeviceiswithintheOperatingRatings.
Specificationsarenotensuredforparameterswherenolimitisgiven,however,thetypicalvalueisagoodindicationofdeviceperformance.
(2)IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexasInstrumentsSalesOffice/Distributorsforavailabilityandspecifications.
(3)TheTO-263PackageisnotrecommendedforVS>16Vduetoimpracticalheatsinkinglimitations.
(4)AllvoltagesaremeasuredwithrespecttotheGNDpin(5),unlessotherwsespecified.
(5)TheoutputsoftheLM4755cannotbedrivenexternallyinanymodewithavoltagelowerthan-0.
4VbelowGNDorpermanentdamagetotheLM4755willresult.
(6)Foroperatingatcasetemperaturesabove25°C,thedevicemustbederatedbasedona150°CmaximumjunctiontemperatureandathermalresistanceofθJC=2°C/W(junctiontocase).
RefertothesectionDETERMININGMAXIMUMPOWERDISSIPATIONintheAPPLICATIONINFORMATIONsectionformoreinformation.
(7)Humanbodymodel,100pFdischargedthrougha1.
5kresistor.
OPERATINGRATINGSTemperatureRangeTMIN≤TA≤TMAX40°C≤TA≤+85°CSupplyVoltage9Vto32VθJC2°C/WθJA76°C/WELECTRICALCHARACTERISTICSThefollowingspecificationsapplytoeachchannelwithVCC=24V,TA=25°Cunlessotherwisespecified.
LM4755UnitsSymbolParameterConditions(Limits)Typical(1)LimitITOTALTotalQuiescentPowerMuteOff1015mA(max)SupplyCurrent7mA(min)MuteOn7mAPOOutputPower(Continuousf=1kHz,THD+N=10%,RL=87WAverageperChannel)f=1kHz,THD+N=10%,RL=41110W(min)VS=20V,RL=84WVS=20V,RL=47Wf=1kHz,THD+N=10%,RL=42.
5WVS=12V,DDPAKPkg.
THDTotalHarmonicDistortionf=1kHz,PO=1W/ch,RL=80.
08%VOSWOutputSwingPO=10W,RL=815VPO=10W,RL=414VXTALKChannelSeparationSeeApps.
Circuit(Figure1)55dBf=1kHz,VO=4Vrms(1)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback3ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comELECTRICALCHARACTERISTICS(continued)ThefollowingspecificationsapplytoeachchannelwithVCC=24V,TA=25°Cunlessotherwisespecified.
LM4755UnitsSymbolParameterConditions(Limits)Typical(1)LimitPSRRPowerSupplyRejectionRatioSeeApps.
Circuit(Figure1)50dBf=120Hz,VO=1mVrmsVODVDifferentialDCOutputOffsetVIN=0V0.
090.
4V(max)VoltageSRSlewRate2V/sRINInputImpedance83kPBWPowerBandwidth3dBBWatPO=2.
5W,RL=865kHzAVCLClosedLoopGain(InternallySet)RL=83433dB(min)35dB(max)εINNoiseIHF-AWeightingFilter,RL=80.
2mVrmsOutputReferredIOOutputShortCircuitLimitVIN=0.
5V,RL=22A(min)MutePinMuteLowInputVoltageNotinMuteMode0.
8V(max)VILVIHMuteHighInputVoltageInMuteMode2.
02.
5V(min)AMMuteAttenuationVMUTE=5.
0V80dBEQUIVALENTSCHEMATICFigure2.
4SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TESTCIRCUITFigure3.
TestCircuitCopyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback5ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comSYSTEMAPPLICATIONCIRCUITFigure4.
CircuitforExternalComponentsDescriptionEXTERNALCOMPONENTSDESCRIPTIONComponentsFunctionDescription1,2CSProvidespowersupplyfilteringandbypassing.
3,4RSNWorkswithCSNtostabilizetheoutputstagefromhighfrequencyoscillations.
5,6CSNWorkswithRSNtostabilizetheoutputstagefromhighfrequencyoscillations.
7CbProvidesfilteringfortheinternallygeneratedhalf-supplybiasgenerator.
8,9CiInputACcouplingcapacitorwhichblocksDCvoltageattheamplifier'sinputterminals.
Alsocreatesahighpassfilterwithfc=1/(2πRinCin).
10,11CoOutputACcouplingcapacitorwhichblocksDCvoltageattheamplifier'soutputterminal.
Createsahighpassfilterwithfc=1/(2πRoutCout).
12,13RiVoltagecontrol-limitsthevoltagelevelallowedtotheamplifier'sinputterminals.
14RmWorkswithCmtoprovidemutefunctiontiming.
15CmWorkswithRmtoprovidemutefunctiontiming.
6SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICSTypicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure5.
Figure6.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure7.
Figure8.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure9.
Figure10.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback7ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comTYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure11.
Figure12.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure13.
Figure14.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure15.
Figure16.
8SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure17.
Figure18.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure19.
Figure20.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure21.
Figure22.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback9ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure23.
Figure24.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure25.
Figure26.
THD+NvsOutputPowerTHD+NvsOutputPowerFigure27.
Figure28.
10SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
OutputPowervsSupplyVoltageOutputPowervsSupplyVoltageFigure29.
Figure30.
FrequencyResponseTHD+NvsFrequencyFigure31.
Figure32.
THD+NvsFrequencyFrequencyResponseFigure33.
Figure34.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comTYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
ChannelSeparationPSRRvsFrequencyFigure35.
Figure36.
SupplyCurrentvsSupplyVoltagePowerDeratingCurveFigure37.
Figure38.
PowerDissipationvsOutputPowerPowerDissipationvsOutputPowerFigure39.
Figure40.
12SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013TYPICALPERFORMANCECHARACTERISTICS(continued)Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
PowerDissipationvsOutputPowerPowerDissipationvsOutputPowerFigure41.
Figure42.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback13ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comAPPLICATIONINFORMATIONTheLM4755containscircuitrytopulldownthebiaslineinternally,effectivelyshuttingdowntheinputstage.
AnexternalR-Cshouldbeusedtoadjustthetimingofthepull-down.
Ifthebiaslineispulleddowntooquickly,currentsinducedintheinternalbiasresistorswillcauseamomentaryDCvoltagetoappearacrosstheinputsofeachamplifier'sinternaldifferentialpair,resultinginanoutputDCshifttowardsVsupply.
AnR-Ctimingcircuitshouldbeusedtolimitthepull-downtimesuchthatoutput"pops"andsignalfeedthroughswillbeminimized.
Thepull-downtimingisafunctionofanumberoffactors,includingtheinternalmutecircuitry,thevoltageusedtoactivatethemute,thebiascapacitor,thehalf-supplyvoltage,andinternalresistancesusedinthehalf-supplygenerator.
Table1showsalistofrecommendedvaluesfortheexternalR-C.
Table1.
RECOMMENDEDVALUESFORMUTECIRCUITVMUTEVCCRmCm5V12V18k10F5V15V18k10F5V20V12k10F5V24V12k10F5V28V8.
2k10F5V30V8.
2k10FCAPACITORSELECTIONANDFREQUENCYRESPONSEWiththeLM4755,asinallsinglesupplyamplifiers,ACcouplingcapacitorsareusedtoisolatetheDCvoltagepresentattheinputs(pins3,7)andoutputs(pins1,8).
AsmentionedearlierintheEXTERNALCOMPONENTSDESCRIPTIONsectionthesecapacitorscreatehigh-passfilterswiththeircorrespondinginput/outputimpedances.
TheTypicalApplicationCircuitshowninFigure1showsinputandoutputcapacitorsof0.
1Fand1,000Frespectively.
Attheinput,withan83ktypicalinputresistance,theresultisahighpass3dBpointoccurringat19Hz.
Thereisanotherhighpassfilterat39.
8Hzcreatedwiththeoutputloadresistanceof4.
Carefulselectionofthesecomponentsisnecessarytoensurethatthedesiredfrequencyresponseisobtained.
TheFrequencyResponsecurvesintheTYPICALPERFORMANCECHARACTERISTICSsectionshowhowdifferentoutputcouplingcapacitorsaffectthelowfrequencyroll-off.
OPERATINGINBRIDGE-MODEThoughdesignedforuseasasingle-endedamplifier,theLM4755canbeusedtodrivealoaddifferentially(bridge-mode).
Duetothelowpincountofthepackage,onlythenon-invertinginputsareavailable.
Aninvertedsignalmustbeprovidedtooneoftheinputs.
Thiscaneasilybedonewiththeuseofaninexpensiveop-ampconfiguredasastandardinvertingamplifier.
AnLF353isagoodlow-costchoice.
Caremustbetaken,however,forabridge-modeamplifiermusttheoreticallydissipatefourtimesthepowerofasingle-endedtype.
Theloadseenbyeachamplifieriseffectivelyhalfthatoftheactualloadbeingused,thusanamplifierdesignedtodrivea4loadinsingle-endedmodeshoulddrivean8loadwhenoperatinginbridge-mode.
14SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013Figure43.
Bridge-ModeApplicationFigure44.
THD+NvsPOUTforBridge-ModeApplicationCopyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback15ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
ti.
comPREVENTINGOSCILLATIONSWiththeintegrationofthefeedbackandbiasresistorson-chip,theLM4755fitsintoaverycompactpackage.
However,duetothecloseproximityofthenon-invertinginputpinstothecorrespondingoutputpins,theinputsshouldbeACterminatedatalltimes.
Iftheinputsareleftfloating,theamplifierwillhaveapositivefeedbackpaththroughhighimpedancecoupling,resultinginahighfrequencyoscillation.
Inmostapplications,thisterminationistypicallyprovidedbythepreviousstage'ssourceimpedance.
Iftheapplicationwillrequireanexternalsignal,theinputsshouldbeterminatedtogroundwitharesistanceof50korlessontheACsideoftheinputcouplingcapacitors.
UNDERVOLTAGESHUTDOWNIfthepowersupplyvoltagedropsbelowtheminimumoperatingsupplyvoltage,theinternalunder-voltagedetectioncircuitrypullsdownthehalf-supplybiasline,shuttingdownthepreampsectionoftheLM4755.
DuetothewideoperatingsupplyrangeoftheLM4755,thethresholdissettojustunder9V.
Theremaybecertainapplicationswhereahigherthresholdvoltageisdesired.
Oneexampleisadesignrequiringahighoperatingsupplyvoltage,withlargesupplyandbiascapacitors,andthereislittleornoothercircuitryconnectedtothemainpowersupplyrail.
Inthiscircuit,whenthepowerisdisconnected,thesupplyandbiascapacitorswilldischargeataslowerrate,possiblyresultinginaudibleoutputdistortionasthedecayingvoltagebeginstocliptheoutputsignal.
Anexternalcircuitmaybeusedtosenseforthedesiredthreshold,andpullthebiasline(pin6)togroundtodisabletheinputpreamp.
Figure45showsanexampleofsuchacircuit.
Whenthevoltageacrossthezenerdiodedropsbelowitsthreshold,currentflowintothebaseofQ1isinterrupted.
Q2thenturnson,dischargingthebiascapacitor.
Thisdischargerateisgovernedbyseveralfactors,includingthebiascapacitorvalue,thebiasvoltage,andtheresistorattheemitterofQ2.
Anequationforapproximatingthevalueoftheemitterdischargeresistor,R,isgivenbelow:R=(0.
7v)/(Cb(VCC/2)/0.
1s)(1)Notethatthisisonlyalinearizedapproximationbasedonadischargetimeof0.
1s.
Thecircuitshouldbeevaluatedandadjustedforeachapplication.
AsmentionedearlierintheBuilt-inMuteCircuitsection,whenusinganexternalcircuittopulldownthebiasline,therateofdischargewillhaveaneffectontheturn-offinduceddistortions.
PleaserefertotheTable1sectionformoreinformation.
Figure45.
ExternalUndervoltagePull-DownTHERMALCONSIDERATIONSHeatSinkingProperheatsinkingisnecessarytoensurethattheamplifierwillfunctioncorrectlyunderalloperatingconditions.
Aheatsinkthatistoosmallwillcausethedietoheatexcessivelyandwillresultinadegradedoutputsignalasthethermalprotectioncircuitrybeginstooperate.
16SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013Thechoiceofaheatsinkforagivenapplicationisdictatedbyseveralfactors:themaximumpowertheICneedstodissipate,theworst-caseambienttemperatureofthecircuit,thejunction-to-casethermalresistance,andthemaximumjunctiontemperatureoftheIC.
Theheatflowapproximationequationusedindeterminingthecorrectheatsinkmaximumthermalresistanceisgivenbelow:TJ–TA=PDMAX(θJC+θCS+θSA)wherePDMAX=maximumpowerdissipationoftheICTJ(°C)=junctiontemperatureoftheICTA(°C)=ambienttemperatureθJC(°C/W)=junction-to-casethermalresistanceoftheICθCS(°C/W)=case-to-heatsinkthermalresistance(typically0.
2to0.
5°C/W)θSA(°C/W)=thermalresistanceofheatsink(2)Whendeterminingtheproperheatsink,theaboveequationshouldbere-writtenas:θSA≤[(TJ–TA)/PDMAX]-θJC–θCS(3)DDPAKHEATSINKINGSurfacemountapplicationswillbelimitedbythethermaldissipationpropertiesofprintedcircuitboardarea.
TheDDPAKpackageisnotrecommendedforsurfacemountapplicationswithVS>16Vduetolimitedprintedcircuitboardarea.
ThereareDDPAKpackageenhancements,suchasclip-onheatsinksandheatsinkswithadhesives,thatcanbeusedtoimproveperformance.
StandardFR-4single-sidedcoppercladwillhaveanapproximateThermalresistance(θSA)rangingfrom:1.
5*1.
5in.
sq.
20–27°C/W(TA=28°C,Sinewavetesting,1oz.
Copper)2*2in.
sq.
16–23°C/WTheabovevaluesforθSAvarywidelyduetodimensionalproportions(i.
e.
variationsinwidthandlengthwillvaryθSA).
Foraudioapplications,wherepeakpowerlevelsareshortinduration,thispartwillperformsatisfactorywithlessheatsinking/coppercladarea.
Aswithanyhighpowerdesignproperbenchtestingshouldbeundertakentoassurethedesigncandissipatetherequiredpower.
Properbenchtestingrequiresattentiontoworstcaseambienttemperatureandairflow.
Athighpowerdissipationlevelsthepartwillshowatendencytoincreasesaturationvoltages,thuslimitingtheundistortedpowerlevels.
DETERMININGMAXIMUMPOWERDISSIPATIONForasingle-endedclassABpoweramplifier,thetheoreticalmaximumpowerdissipationpointisafunctionofthesupplyvoltage,VS,andtheloadresistance,RLandisgivenbythefollowingequation:(singlechannel)PDMAX(W)=[VS2/(2π2RL)]Theaboveequationisforasinglechannelclass-ABpoweramplifier.
FordualamplifierssuchastheLM4755,theequationforcalculatingthetotalmaximumpowerdissipatedis:(dualchannel)PDMAX(W)=2[VS2/(2π2RL)]orVS2/(π2RL)(BridgedOutputs)PDMAX(W)=4[VS2/(2π2RL)]Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback17ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comHEATSINKDESIGNEXAMPLEDeterminethesystemparameters:VS=24VOperatingSupplyVoltageRL=4MinimumLoadImpedanceTA=55°CWorstCaseAmbientTemperatureDeviceparametersfromthedatasheet:TJ=150°CMaximumJunctionTemperatureθJC=2°C/WJunction-to-CaseThermalResistanceCalculations:2PDMAX=2[VS2/2π2RL)]=(24V)2/(2π24)=14.
6WθSA≤[(TJ-TA)/PDMAX]-θJC–θCS=[(150°C-55°C)/14.
6W]-2°C/W–0.
2°C/W=4.
3°C/WConclusion:ChooseaheatsinkwithθSA≤4.
3°C/W.
DDPAKHEATSINKDESIGNEXAMPLESExample1:(StereoSingle-EndedOutput)Given:TA=30°CTJ=150°CRL=4VS=12VθJC=2°C/WPDMAXfromPDvsPOGraph:PDMAX≈3.
7W(4)CalculatingPDMAX:PDMAX=VCC2/(π2RL)=(12V)2/π2(4))=3.
65W(5)CalculatingHeatsinkThermalResistance:θSA
0°C/W0.
2°C/W=30.
2°C/W(7)Thereforetherecommendationistouse1.
5*1.
5squareinchofsingle-sidedcopperclad.
Example2:(StereoSingle-EndedOutput)Given:TA=50°CTJ=150°CRL=4VS=12VθJC=2°C/WPDMAXfromPDvsPOGraph:PDMAX≈3.
7W(8)CalculatingPDMAX:PDMAX=VCC2/(π2RL)=(12V)2/(π2(4))=3.
65W(9)CalculatingHeatsinkThermalResistance:θSA<[(TJTA)/PDMAX]θJCθCS(10)18SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013θSA<100°C/3.
7W2.
0°C/W0.
2°C/W=24.
8°C/W(11)Thereforetherecommendationistouse2.
0*2.
0squareinchofsingle-sidedcopperclad.
Example3:(BridgedOutput)Given:TA=50°CTJ=150°CRL=8VS=12VθJC=2°C/WCalculatingPDMAX:PDMAX=4[VCC2/(2π2RL)]=4(12V)2/(2π2(8))=3.
65W(12)CalculatingHeatsinkThermalResistance:θSA<[(TJTA)/PDMAX]θJCθCS(13)θSA<100°C/3.
7W2.
0°C/W0.
2°C/W=24.
8°C/W(14)Thereforetherecommendationistouse2.
0*2.
0squareinchofsingle-sidedcopperclad.
LAYOUTANDGROUNDRETURNSProperPCboardlayoutisessentialforgoodcircuitperformance.
WhenlayingoutaPCboardforanaudiopoweramplifier,particularattentionmustbepaidtotheroutingoftheoutputsignalgroundreturnsrelativetotheinputsignalandbiascapacitorgrounds.
Topreventanygroundloops,thegroundreturnsfortheoutputsignalsshouldberoutedseparatelyandbroughttogetheratthesupplyground.
Theinputsignalgroundsandthebiascapacitorgroundlineshouldalsoberoutedseparately.
The0.
1FhighfrequencysupplybypasscapacitorshouldbeplacedascloseaspossibletotheIC.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback19ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comPCBOARDLAYOUT-COMPOSITEFigure46.
20SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
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comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013PCBOARDLAYOUT-SILKSCREENFigure47.
Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback21ProductFolderLinks:LM4755LM4755SNAS010E–FEBRUARY1999–REVISEDAPRIL2013www.
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comPCBOARDLAYOUT-SOLDERSIDEFigure48.
22SubmitDocumentationFeedbackCopyright1999–2013,TexasInstrumentsIncorporatedProductFolderLinks:LM4755LM4755www.
ti.
comSNAS010E–FEBRUARY1999–REVISEDAPRIL2013REVISIONHISTORYChangesfromRevisionD(April2013)toRevisionEPageChangedlayoutofNationalDataSheettoTIformat22Copyright1999–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback23ProductFolderLinks:LM4755PACKAGEOPTIONADDENDUMwww.
ti.
com10-Dec-2020Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Leadfinish/Ballmaterial(6)MSLPeakTemp(3)OpTemp(°C)DeviceMarking(4/5)SamplesLM4755TSX/NOPBACTIVEDDPAK/TO-263KTW9500RoHS-Exempt&GreenSNLevel-3-245C-168HR-20to80LM4755TS(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)RoHS:TIdefines"RoHS"tomeansemiconductorproductsthatarecompliantwiththecurrentEURoHSrequirementsforall10RoHSsubstances,includingtherequirementthatRoHSsubstancedonotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,"RoHS"productsaresuitableforuseinspecifiedlead-freeprocesses.
TImayreferencethesetypesofproductsas"Pb-Free".
RoHSExempt:TIdefines"RoHSExempt"tomeanproductsthatcontainleadbutarecompliantwithEURoHSpursuanttoaspecificEURoHSexemption.
Green:TIdefines"Green"tomeanthecontentofChlorine(Cl)andBromine(Br)basedflameretardantsmeetJS709Blowhalogenrequirementsof<=1000ppmthreshold.
Antimonytrioxidebasedflameretardantsmustalsomeetthe<=1000ppmthresholdrequirement.
(3)MSL,PeakTemp.
-TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)Theremaybeadditionalmarking,whichrelatestothelogo,thelottracecodeinformation,ortheenvironmentalcategoryonthedevice.
(5)MultipleDeviceMarkingswillbeinsideparentheses.
OnlyoneDeviceMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireDeviceMarkingforthatdevice.
(6)Leadfinish/Ballmaterial-OrderableDevicesmayhavemultiplematerialfinishoptions.
Finishoptionsareseparatedbyaverticalruledline.
Leadfinish/Ballmaterialvaluesmaywraptotwolinesifthefinishvalueexceedsthemaximumcolumnwidth.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.
TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
Effortsareunderwaytobetterintegrateinformationfromthirdparties.
TIhastakenandcontinuestotakereasonablestepstoproviderepresentativeandaccurateinformationbutmaynothaveconducteddestructivetestingorchemicalanalysisonincomingmaterialsandchemicals.
TIandTIsuppliersconsidercertaininformationtobeproprietary,andthusCASnumbersandotherlimitedinformationmaynotbeavailableforrelease.
InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
TAPEANDREELINFORMATION*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQReelDiameter(mm)ReelWidthW1(mm)A0(mm)B0(mm)K0(mm)P1(mm)W(mm)Pin1QuadrantLM4755TSX/NOPBDDPAK/TO-263KTW9500330.
024.
410.
7514.
855.
016.
024.
0Q2PACKAGEMATERIALSINFORMATIONwww.
ti.
com8-Nov-2013PackMaterials-Page1*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQLength(mm)Width(mm)Height(mm)LM4755TSX/NOPBDDPAK/TO-263KTW9500367.
0367.
045.
0PACKAGEMATERIALSINFORMATIONwww.
ti.
com8-Nov-2013PackMaterials-Page2MECHANICALDATAKTW0009Awww.
ti.
comBOTTOMSIDEOFPACKAGETS9A(RevB)IMPORTANTNOTICEANDDISCLAIMERTIPROVIDESTECHNICALANDRELIABILITYDATA(INCLUDINGDATASHEETS),DESIGNRESOURCES(INCLUDINGREFERENCEDESIGNS),APPLICATIONOROTHERDESIGNADVICE,WEBTOOLS,SAFETYINFORMATION,ANDOTHERRESOURCES"ASIS"ANDWITHALLFAULTS,ANDDISCLAIMSALLWARRANTIES,EXPRESSANDIMPLIED,INCLUDINGWITHOUTLIMITATIONANYIMPLIEDWARRANTIESOFMERCHANTABILITY,FITNESSFORAPARTICULARPURPOSEORNON-INFRINGEMENTOFTHIRDPARTYINTELLECTUALPROPERTYRIGHTS.
TheseresourcesareintendedforskilleddevelopersdesigningwithTIproducts.
Youaresolelyresponsiblefor(1)selectingtheappropriateTIproductsforyourapplication,(2)designing,validatingandtestingyourapplication,and(3)ensuringyourapplicationmeetsapplicablestandards,andanyothersafety,security,orotherrequirements.
Theseresourcesaresubjecttochangewithoutnotice.
TIgrantsyoupermissiontousetheseresourcesonlyfordevelopmentofanapplicationthatusestheTIproductsdescribedintheresource.
Otherreproductionanddisplayoftheseresourcesisprohibited.
NolicenseisgrantedtoanyotherTIintellectualpropertyrightortoanythirdpartyintellectualpropertyright.
TIdisclaimsresponsibilityfor,andyouwillfullyindemnifyTIanditsrepresentativesagainst,anyclaims,damages,costs,losses,andliabilitiesarisingoutofyouruseoftheseresources.
TI'sproductsareprovidedsubjecttoTI'sTermsofSale(www.
ti.
com/legal/termsofsale.
html)orotherapplicabletermsavailableeitheronti.
comorprovidedinconjunctionwithsuchTIproducts.
TI'sprovisionoftheseresourcesdoesnotexpandorotherwisealterTI'sapplicablewarrantiesorwarrantydisclaimersforTIproducts.
MailingAddress:TexasInstruments,PostOfficeBox655303,Dallas,Texas75265Copyright2020,TexasInstrumentsIncorporated
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