LM4781 Overture Audio Pwr Amp Series 3 Chan 35W Audio Pwr Amp w/Mute

32 Pages·2017·1.66 MB·English

LM4781, LM4781TABD
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LM4781 Overture™ Audio Power Amplifier Series 3 Channel 35W Audio Power Amplifier
with Mute
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FEATURES DESCRIPTION
1
• SPiKeProtection The LM4781 is a three channel audio amplifier
23 capable of typically delivering 35W per channel of
• LowExternalComponentCount
continuous average output power into an 8Ω load
• QuietFade-In/OutMuteMode withlessthan0.5% THD+Nfrom20Hz-20kHz.
• WideSupply Range:20V-70V
The LM4781 is fully protected utilizing TI's Self Peak
• Signal-to-Noise Ratio≥ 93dB(ref.toP =1W) Instantaneous Temperature (°Ke) (SPiKe) protection
O
circuitry. SPiKe provides a dynamically optimized
APPLICATIONS Safe Operating Area (SOA). SPiKe protection
completely safeguards the LM4781's outputs against
• AudioAmplifier forComponentStereo
over-voltage, under-voltage, overloads, shorts to the
• AudioAmplifier forCompactStereo supplies or GND, thermal runaway and instantaneous
• AudioAmplifier forSelf-PoweredSpeakers temperature peaks. The advanced protection features
of the LM4781 places it in a class above discrete and
• AudioAmplifier forHigh-Endand HDTVs
hybridamplifiers.
KEY SPECIFICATIONS Each amplifier of the LM4781 has an independent
smoothtransitionfade-in/outmute.
• Output Power/Channelwith0.5%THD+N, 1kHz
into8Ω:35W(typ) The LM4781 can easily be configured for bridge or
parallel operation for higher power and bi-amp
• THD+Nat3x20Winto8Ω(20Hz-20kHz): 0.2%
solutions.
(typ)
• THD+Nat3x20Winto6Ω(20Hz-20kHz): 0.3%
(typ)
• THD+Nat3x20Winto4Ω(20Hz-20kHz): 0.5%
(typ)
• MuteAttenuation:110dB(typ)
• PSRR:85dB(min)
• SlewRate:9V/μs(typ)
1
Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsof
TexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
Overtureisatrademarkofdcl_owner.
2
Allothertrademarksarethepropertyoftheirrespectiveowners.
3
PRODUCTIONDATAinformationiscurrentasofpublicationdate. Copyright©2003–2013,TexasInstrumentsIncorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarilyincludetestingofallparameters.
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Typical Application
Figure1. TypicalAudioAmplifierApplicationCircuit
Connection Diagram
Figure2. PlasticTO-220Package–TopView
SeePackageNumber NDM0027A(1)
(1) TheNDM0027Aisanon-isolatedpackage.Thepackage'smetalbackandanyheatsinktowhichitismountedareconnectedtotheV-
potentialwhenusingonlythermalcompound.Ifamicawasherisusedinadditiontothermalcompound,θ (casetosink)isincreased,
CS
buttheheatsinkwillbeelectricallyisolatedfromV-.
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Thesedeviceshavelimitedbuilt-inESDprotection.Theleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoam
duringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
Absolute Maximum Ratings(1)(2)(3)
SupplyVoltage|V+|+|V-| (NoSignal) 72V
SupplyVoltage|V+|+|V-| (InputSignal) 70V
CommonModeInputVoltage (V+orV-)and
|V+|+|V-|≤60V
DifferentialInputVoltage(4) 60V
OutputCurrent InternallyLimited
PowerDissipation(5) 125W
ESDSusceptability(6) 2.0kV
ESDSusceptability(7) 200V
JunctionTemperature(T )(8) 150°C
JMAX
SolderingInformation TAPackage(10seconds) 260°C
StorageTemperature -40°Cto+150°C
ThermalResistance(9) θ 30°C/W
JA
θ 0.9°C/W
JC
(1) AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsfor
whichthedeviceisfunctional,butdonotensurespecificperformancelimits.ElectricalCharacteristicsstateDCandACelectrical
specificationsunderparticulartestconditionswhichensurespecificperformancelimits.Thisassumesthatthedeviceiswithinthe
OperatingRatings.Specificationsarenotensuredforparameterswherenolimitisgiven;however,thetypicalvalueisagoodindication
ofdeviceperformance.
(2) Allvoltagesaremeasuredwithrespecttothegroundpins,unlessotherwisespecified.
(3) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexasInstrumentsSalesOffice/Distributorsforavailabilityand
specifications.
(4) TheDifferentialInputVoltageAbsoluteMaximumRatingisbasedonsupplyvoltagesV+=30VandV-=-30V.
(5) Themaximumpowerdissipationmustbede-ratedatelevatedtemperaturesandisdictatedbyT ,θ ,andtheambienttemperature
JMAX JC
T .ThemaximumallowablepowerdissipationisP =(T -T )/θ orthenumbergivenintheAbsoluteMaximumRatings,
A DMAX JMAX A JC
whicheverislower.FortheLM4781,T =150°Candthetypicalθ is0.9°C/W.RefertotheDETERMININGTHECORRECTHEAT
JMAX JC
SINKsectionformoreinformation.
(6) Humanbodymodel,100pFdischargedthrougha1.5kΩresistor.
(7) MachineModel:a220pF-240pFdischargedthroughallpins.
(8) Themaximumoperatingjunctiontemperatureis150°C.However,theinstantaneousSafeOperatingAreatemperatureis250°C.
(9) TheNDM0027Aisanon-isolatedpackage.Thepackage'smetalbackandanyheatsinktowhichitismountedareconnectedtotheV-
potentialwhenusingonlythermalcompound.Ifamicawasherisusedinadditiontothermalcompound,θ (casetosink)isincreased,
CS
buttheheatsinkwillbeelectricallyisolatedfromV-.
Operating Ratings(1)(2)(3)
TemperatureRange T ≤T ≤T −20°C≤T ≤+85°C
MIN A MAX A
SupplyVoltage|V+|+|V-| 20V≤V ≤70V
TOTAL
(1) Allvoltagesaremeasuredwithrespecttothegroundpins,unlessotherwisespecified.
(2) AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsfor
whichthedeviceisfunctional,butdonotensurespecificperformancelimits.ElectricalCharacteristicsstateDCandACelectrical
specificationsunderparticulartestconditionswhichensurespecificperformancelimits.Thisassumesthatthedeviceiswithinthe
OperatingRatings.Specificationsarenotensuredforparameterswherenolimitisgiven;however,thetypicalvalueisagoodindication
ofdeviceperformance.
(3) Operationisensuredupto70V;however,distortionmaybeintroducedfromSPiKeprotectioncircuitryifproperthermalconsiderations
arenottakenintoaccount.RefertotheTHERMALPROTECTIONsectionformoreinformation.
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Electrical Characteristics(1)(2)
ThefollowingspecificationsapplyforV+=+28V,V-=−28V,I =-1mA/channelandR =8Ωunlessotherwisespecified.
MUTE L
LimitsapplyforT =25°C.
A
LM4781 Units
Symbol Parameter Conditions
Typical(3) Limit(4)(5) (Limits)
|V+|+|V-| PowerSupplyVoltage(6) GND−V-≥9V 18 20 V(min)
70 V(max)
A MuteAttenuation I =0mA 110 80 dB(min)
M MUTE
THD+N=0.5%(max)
f=1kHz
P OutputPower(RMS) |V+|=|V-|=20V,R =4Ω 25 20 W(min)
O L
|V+|=|V-|=24V,R =6Ω 30 25 W(min)
L
|V+|=|V-|=28V,R =8Ω 35 30 W(min)
L
P =20W,f=20Hz-20kHz
O
A =26dB
THD+N TotalHarmonicDistortion+ |VV+|=|V-|=20V,R =4Ω 0.5 %
Noise |V+|=|V-|=24V,RL=6Ω 0.3 %
L
|V+|=|V-|=28V,R =8Ω 0.2 %
L
P =10W,f=1kHz 70 dB
X ChannelSeparation(7) O
talk
P =10W,f=10kHz 66 dB
O
SR SlewRate V =1.2V ,f=10kHzsquare 9 5 V/μs(min)
IN RMS
Wave.R =2kΩ
L
I TotalQuiescentPower V =0V 75 150 mA(max)
DD CM
SupplyCurrent V =0V,I =0A
O O
V InputOffsetVoltage V =0V,I =0mA 1 10 mV(max)
OS CM O
I InputBiasCurrent V =0V,I =0mA 0.2 1 μA(max)
B CM O
I OutputCurrentLimit |V+|=|V-|=20V,t =10ms 4 3 A(min)
O ON
VOD OutputDropoutVoltage(8) ||VV+--VVO-||,,VV-=+=-2200VV,,IIO==-1+0100m0mAA 12..55 44 VV((mmaaxx))
O O
V+=30Vto10V,V-=-30V
125 85 dB(min)
V =0V,I =0mA
PSRR PowerSupplyRejectionRatio(9) CM O
V+=30V,V-=-30Vto-10V
110 85 dB(min)
V =0V,I =0mA
CM O
CMRR CommonModeRejectionRatio(9) V+=30Vto10V,V-=-10Vto-30V 110 75 dB(min)
V =20Vto-20V,I =0mA
CM O
A OpenLoopVoltageGain |V+|=|V-|=28V,R =2kΩ
VOL L 115 80 dB(min)
ΔV =20V
O
GBWP GainBandwidthProduct |V+|=|V-|=28V,f =100kHz 8 2 MHz(min)
IN
V =50mV
IN RMS
e InputNoise IHF-A-WeightingFilter, 3.0 8 μV(max)
IN
R =600Ω(InputReferred)
IN
(1) Allvoltagesaremeasuredwithrespecttothegroundpins,unlessotherwisespecified.
(2) AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsfor
whichthedeviceisfunctional,butdonotensurespecificperformancelimits.ElectricalCharacteristicsstateDCandACelectrical
specificationsunderparticulartestconditionswhichensurespecificperformancelimits.Thisassumesthatthedeviceiswithinthe
OperatingRatings.Specificationsarenotensuredforparameterswherenolimitisgiven;however,thetypicalvalueisagoodindication
ofdeviceperformance.
(3) Typicalspecificationsaremeasuredat25°Candrepresenttheparametricnorm.
(4) TestedlimitsarespecifiedtoTI'sAOQL(AverageOutgoingQualityLevel).
(5) Datasheetmin/maxspecificationlimitsarespecifiedbydesign,test,orstatisticalanalysis.
(6) V-musthaveatleast-9VatitspinwithreferencetoGNDinorderfortheunder-voltageprotectioncircuitrytobedisabled.Inaddition,
thevoltagedifferentialbetweenV+andV-mustbegreaterthan14V.
(7) Crosstalkperformancewasmeasuredusingthedemoboardshowninthedatasheet.PCBlayoutwillaffectcrosstalk.Itis
recommendedthattheinputandoutputtracesbeseparatedbyasmuchdistanceaspossible.Returngroundtracesfromoutputsshould
alsobeindependentbacktosinglegroundpointanduseaswideoftracesaspossible.
(8) Theoutputdropoutvoltageisthesupplyvoltageminustheclippingvoltage.RefertotheClippingVoltagevs.SupplyVoltagegraphin
theTypicalPerformanceCharacteristicssection.
(9) DCelectricaltest.
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Electrical Characteristics(1)(2) (continued)
ThefollowingspecificationsapplyforV+=+28V,V-=−28V,I =-1mA/channelandR =8Ωunlessotherwisespecified.
MUTE L
LimitsapplyforT =25°C.
A
LM4781 Units
Symbol Parameter Conditions
Typical(3) Limit(4)(5) (Limits)
P =1W ;A-WeightedFilter
O RMS 93 dB
f =1kHz,R =25Ω
IN S
SNR Signal-to-NoiseRatio
P =25W ;A-WeightedFilter
O RMS 107 dB
f =1kHz,R =25Ω
IN S
60Hz,7kHz,4:1(SMPTE) 0.004 %
IMD IntermodulationDistortion
60Hz,7kHz,1:1(SMPTE) 0.006 %
Bridged Amplifier Application Circuit
Figure3. BridgedAmplifier ApplicationCircuit
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Parallel Amplifier Application Circuit
Figure4. Parallel Amplifier ApplicationCircuit
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Single Supply Application Circuit
Figure5. SingleSupply Amplifier ApplicationCircuit
NOTE
*Optionalcomponentsdependentuponspecific designrequirements.
Auxiliary Amplifier Application Circuit
Figure6. SpecialAudioAmplifierApplicationCircuit
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External Components Description
Figure1,Figure3,Figure4,Figure5,andFigure6
Components FunctionalDescription
1 R Preventscurrentfromenteringtheamplifier'snon-invertinginput.Thiscurrentmaypassthroughtotheloadduring
B
systempowerdown,becauseoftheamplifier'slowinputimpedancewhentheundervoltagecircuitryisoff.This
phenomenonoccurswhentheV+andV-supplyvoltagesarebelow1.5V.
2 R Invertinginputresistance.AlongwithR,setsACgain.
i f
3 R Feedbackresistance.AlongwithR,setsACgain.
f i
4 R Feedbackresistance.WorkswithCfandRfcreatingalowpassfilterthatlowersACgainathighfrequencies.The-
f2
(1) 3dBpointofthepoleoccurswhen:(R -R)/2=R //[1/(2πfC)+R ]fortheNon-Invertingconfigurationshownin
f i f c f f2
Figure6.
5 C Compensationcapacitor.WorkswithR andR toreduceACgainathigherfrequencies.
f f f2
(1)
6 C Compensationcapacitor.Reducesthegainathigherfrequenciestoavoidquasi-saturationoscillationsoftheoutput
C
(1) transistor.Alsosuppressesexternalelectromagneticswitchingnoisecreatedfromfluorescentlamps.
7 C FeedbackcapacitorwhichensuresunitygainatDC.AlongwithR alsocreatesahighpassfilteratf =1/(2πRC).
i i c i i
(1)
8 C Providespowersupplyfilteringandbypassing.RefertotheSUPPLYBYPASSINGapplicationsectionforproper
S
placementandselectionofbypasscapacitors.
9 R Actsasavolumecontrolbysettingtheinputvoltagelevel.
V
(1)
10 R Setstheamplifier'sinputterminalsDCbiaspointwhenC ispresentinthecircuit.AlsoworkswithC tocreatea
IN IN IN
(1) highpassfilteratf =1/(2πR C ).IfthevalueofR istoolarge,oscillationsmaybeobservedontheoutputs
C IN IN IN
whentheinputsarefloating.Recommendedvaluesare10kΩto47kΩ.RefertoFigure6.
11 C Inputcapacitor.Preventstheinputsignal'sDCoffsetsfrombeingpassedontotheamplifier'sinputs.
IN
(1)
12 R WorkswithC tostabilizetheoutputstagebycreatingapolethatreduceshighfrequencyinstabilities.
SN SN
(1)
13 C WorkswithR tostabilizetheoutputstagebycreatingapolethatreduceshighfrequencyinstabilities.Thepoleis
SN SN
(1) setatf =1/(2πR C ).RefertoFigure6.
C SN SN
14 L (1) ProvideshighimpedanceathighfrequenciessothatRmaydecoupleahighlycapacitiveloadandreducetheQof
15 R (1) theseriesresonantcircuit.AlsoprovidesalowimpedanceatlowfrequenciestoshortoutRandpassaudiosignals
totheload.RefertoFigure6.
16 R ProvidesDCvoltagebiasingforthetransistorQ1insinglesupplyoperation.
A
17 C Providesbiasfilteringforsinglesupplyoperation.
A
18 R Limitsthevoltagedifferencebetweentheamplifier'sinputsforsinglesupplyoperation.RefertotheCLICKSAND
INP
(1) POPSapplicationsectionforamoredetailedexplanationofthefunctionofR .
INP
19 R Providesinputbiascurrentforsinglesupplyoperation.RefertotheCLICKSANDPOPSapplicationsectionfora
BI
moredetailedexplanationofthefunctionofR .
BI
20 R EstablishesafixedDCcurrentforthetransistorQ1insinglesupplyoperation.Thisresistorstabilizesthehalf-
E
supplypointalongwithC .
A
21 R Muteresistancesetuptoallow0.5mAtobedrawnfromeachMUTEpintoturnthemutingfunctionoff.
M
→R iscalculatedusing:R ≤(|V |−2.6V)/lwherel≥0.5mA.RefertotheMuteAttenuationvsMuteCurrent
M M EE
curvesintheTypicalPerformanceCharacteristicssection.
22 C Mutecapacitancesetuptocreatealargetimeconstantforturn-onandturn-offmuting.
M
23 S Muteswitch.WhenopenorswitchedtoGND,theamplifierwillbeinmutemode.
1
24 R ReducescurrentflowbetweenoutputsthatarecausedbyGainorDCoffsetdifferencesbetweentheamplifiers.
OUT
(1) Optionalcomponentsdependentuponspecificdesignrequirements.
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Optional External Component Interaction
Although the optional external components have specific desired functions that are designed to reduce the
bandwidth and eliminate unwanted high frequency oscillations they may cause certain undesirable effects when
theyinteract.Interactionmayoccurforcomponentswhosereactancesareincloseproximitytooneanother.One
examplewouldbethecouplingcapacitor,C ,andthecompensationcapacitor, C.Thesetwocomponentsact as
C f
low impedances to certain frequencies which will couple signals from the input to the output. Please take careful
noteofbasicamplifiercomponentfunctionalitywhendesigninginthesecomponents.
The optional external components shown in Figure 5 and Figure 6 and described above are applicable in both
singleandsplitvoltagesupplyconfigurations.
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Typical Performance Characteristics
THD+N THD+N
vs vs
Frequency Frequency
±20V,P =1W&20W/Channel ±24V,P =1W&20W/Channel
OUT OUT
R =4Ω,80kHzBW R =6Ω,80kHzBW
L L
Figure7. Figure8.
THD+N
vs THD+N
Frequency vs
±28V,P =1W&20W/Channel OutputPower/Channel
OUT
R =8Ω,80kHzBW ±20V,R =4Ω,80kHzBW
L L
Figure9. Figure10.
THD+N THD+N
vs vs
OutputPower/Channel OutputPower/Channel
±24V,R =6Ω,80kHzBW ±28V,R =8Ω,80kHzBW
L L
Figure11. Figure12.
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