LM3875 Overture Audio Power Amp Series HPerformance 56W Audio Power Amp

30 Pages·2017·0.81 MB·English

LM3875
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LM3875 Overture™ Audio Power Amplifier Series
High-Performance 56W Audio Power Amplifier
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FEATURES DESCRIPTION
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• 56WContinuousAverageOutputPowerInto The LM3875 is a high-performance audio power
23 amplifier capable of delivering 56W of continuous
8Ω
average power to an 8Ω load with 0.1% THD+N from
• 100WInstantaneousPeakOutputPower
20Hzto20kHz.
Capability
The performance of the LM3875, utilizing its Self
• Signal-to-Noise Ratio>95dB(min)
Peak Instantaneous Temperature (°Ke) (SPiKe)
• Output ProtectionFromAShorttoGroundor protection circuitry, puts it in a class above discrete
totheSuppliesViaInternalCurrentLimiting and hybrid amplifiers by providing an inherently,
Circuitry dynamically protected Safe Operating Area (SOA).
SPiKe protection means that these parts are
• Output Over-VoltageProtectionAgainst
completely safeguarded at the output against
TransientsFromInductiveLoads
overvoltage, undervoltage, overloads, caused by
• SupplyUnder-VoltageProtection,NotAllowing
shorts to the supplies, thermal runaway, and
InternalBiasingtoOccur When|V+|+|V−|≤ instantaneoustemperaturepeaks.
12V,ThusEliminatingTurn-OnandTurn-Off
The LM3875 maintains an excellent signal-to-noise
Transients
ratio of greater than 95dB(min) with a typical low
• 11LeadPFMPackage noise floor of 2.0μV. It exhibits extremely low THD+N
• WideSupply VoltageRange:|V+|+|V−|=20V values of 0.06% at the rated output into the rated
to84V load over the audio spectrum, and provides excellent
linearity with an IMD (SMPTE) typical rating of
APPLICATIONS 0.004%.
• Componentor CompactStereos
• Self-PoweredSpeakers
• Surround-SoundAmplifiers
• High-EndStereoTVs
1
Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsof
TexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
OvertureisatrademarkofTexasInstruments.
2
Allothertrademarksarethepropertyoftheirrespectiveowners.
3
PRODUCTIONDATAinformationiscurrentasofpublicationdate. Copyright©1999–2013,TexasInstrumentsIncorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarilyincludetestingofallparameters.
LM3875
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Typical Application
*Optionalcomponentsdependentuponspecificdesignrequirements.RefertotheExternalComponentsDescription
sectionforacomponentfunctiondescription.
Figure1. TypicalAudioAmplifierApplicationCircuit
Connection Diagram
Figure2. PlasticPackage(1)-TopView
SeePackageNumber NDJfor
StaggeredLeadNon-IsolatedPackage
or NDA0011BforStaggeredLeadIsolatedPackage
(1) TheLM3875Tpackage(NDJ)isanon-isolatedpackage,settingthetabofthedeviceandtheheatsinkatV−potentialwhenthe
LM3875isdirectlymountedtotheheatsinkusingonlythermalcompound.Ifamicawasherisusedinadditiontothermalcompound,
θ (casetosink)isincreased,buttheheatsinkwillbeisolatedfromV−.
CS
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Equivalent Schematic
(Excludingactiveprotectioncircuitry)
Thesedeviceshavelimitedbuilt-inESDprotection.Theleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoam
duringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
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Absolute Maximum Ratings(1)(2)(3)
SupplyVoltage|V+|+|V−|(NoSignal) 94V
SupplyVoltage|V+|+|V−|(InputSignal) 84V
CommonModeInputVoltage (V+orV−)and|V+|+|V−|≤80V
DifferentialInputVoltage 60V
OutputCurrent InternallyLimited
PowerDissipation(4) 125W
ESDSusceptibility(5) 2500V
JunctionTemperature(6) 150°C
SolderingInformation Tpackage(10seconds) 260°C
StorageTemperature −40°Cto+150°C
θ 1°C/W
JC
ThermalResistance
θ 43°C/W
JA
(1) AllvoltagesaremeasuredwithrespecttosupplyGND,unlessotherwisespecified.
(2) IfMilitary/Aerospacespecifieddevicesarerequired,pleasecontacttheTexasInstrumentsSalesOffice/Distributorsforavailabilityand
specifications.
(3) AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsfor
whichthedeviceisfunctional,butdonotensurespecificperformancelimits.ElectricalCharacteristicsstateDCandACelectrical
specificationsunderparticulartestconditionswhichensurespecificperformancelimits.Thisassumesthatthedeviceiswithinthe
OperatingRatings.Specificationsarenotensuredforparameterswherenolimitisgiven,however,thetypicalvalueisagoodindication
ofdeviceperformance.
(4) Foroperatingatcasetemperaturesabove25°C,thedevicemustbederatedbasedona150°Cmaximumjunctiontemperatureanda
thermalresistanceofθ =1.0°C/W(junctiontocase).RefertotheThermalResistancefigureintheApplicationInformationsection
JC
underTHERMALCONSIDERATIONS.
(5) Humanbodymodel,100pFdischargedthrougha1.5kΩresistor.
(6) Theoperatingjunctiontemperaturemaximumis150°C,however,theinstantaneousSafeOperatingAreatemperatureis250°C.
Operating Ratings(1)(2)(3)
TemperatureRange(T ≤T ≤T ) −20°C≤T ≤+85°C
MIN A MAX A
SupplyVoltage|V+|+|V−| 20Vto84V
(1) AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsfor
whichthedeviceisfunctional,butdonotensurespecificperformancelimits.ElectricalCharacteristicsstateDCandACelectrical
specificationsunderparticulartestconditionswhichensurespecificperformancelimits.Thisassumesthatthedeviceiswithinthe
OperatingRatings.Specificationsarenotensuredforparameterswherenolimitisgiven,however,thetypicalvalueisagoodindication
ofdeviceperformance.
(2) AllvoltagesaremeasuredwithrespecttosupplyGND,unlessotherwisespecified.
(3) Operationisensuredupto84V,however,distortionmaybeintroducedfromtheSPiKeProtectionCircuitrywhenoperatingabove70Vif
properthermalconsiderationsarenottakenintoaccount.RefertotheTHERMALCONSIDERATIONSsectionformoreinformation.
(SeeSPiKeProtectionResponse)
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Electrical Characteristics(1)(2)
ThefollowingspecificationsapplyforV+=+35V,V−=−35VwithR =8Ωunlessotherwisespecified.LimitsapplyforT =
L A
25°C.
LM3875 Units
Symbol Parameter Conditions
Typical(3) Limit(4) (Limits)
|V+|+|V−| PowerSupplyVoltage 20 V(Min)
84 V(Max)
P (5) OutputPower(ContinuousAverage) THD+N=0.1%(Max)
O 56 40 W(Min)
f=1kHz,f=20kHz
PeakP InstantaneousPeakOutputPower 100 W
O
THD+N TotalHarmonicDistortionPlusNoise 40W,20Hz≤f≤20kHz
0.06 %
A =26dB
V
SR(5) SlewRate(6) V =1.414Vrms,f=10kHz
IN 11 5 V/µs(Min)
Square-wave,R =2kΩ
L
I+ TotalQuiescentPowerSupply V =0V,V =0V,I =0mA
Current(7) CM O o 30 70 mA(Max)
V 1 10 mV(Max)
OS
InputOffset V =0V,I =0mA V =0V,I =0mA
Voltage(7) CM o CM o 0.2 1 µA(Max)
I InputOffsetCurrent V =0V,I =0mA 0.01 0.2 µA(Max)
OS CM o
I OutputCurrentLimit |V+|=|V−|=10V,t =10ms,V =0V 6 4 A(Min)
o on O
V (7) OutputDropoutVoltage(8) |V+−V −|,V+=20V,I =+100mA 1.6 5 V(Max)
od o o
|V −V−|,V−=−20V,I =−100mA 2.7 5 V(Max)
o o
V+=40Vto20V,V−=−40V,
PSRR V =0V,I =0mA 120 85
Ratio(7) PowerSupplyRejection Vc+m=40V,Vo=−40Vto−20V, 120 85 dB(Min)
V =0V,I =0mA
cm o
CMRR(7) CommonModeRejectionRatio V+=60Vto20V,V−=−20Vto−60V, 120 80 dB(Min)
V =20Vto−20V,I =0mA
cm o
A (7) OpenLoopVoltageGain |V+|=|V−|=40V,R =2kΩ,ΔV =60V 120 90 dB(Min)
VOL L O
|V+|=|V−|=40V
GBWP Gain-BandwidthProduct 8 2 MHz(Min)
f =100kHz,V =50mVrms
O IN
e (5) InputNoise IHF−AWeightingFilter 2.0 8.0 µV(Max)
IN R =600Ω(InputReferred)
IN
Signal-to-NoiseRatio P =1W,A-Weighted,
O 98dB dB
Measuredat1kHz,R =25Ω
S
P =40W,A-Weighted,
SNR O 114dB dB
Measuredat1kHz,R =25Ω
S
P =100W,A-Weighted,
pk 122dB dB
Measuredat1kHz,R =25Ω
S
60Hz,7kHz,4:1(SMPTE) 0.004
IMD IntermodulationDistortionTest %
60Hz,7kHz,1:1(SMPTE) 0.006
(1) AbsoluteMaximumRatingsindicatelimitsbeyondwhichdamagetothedevicemayoccur.OperatingRatingsindicateconditionsfor
whichthedeviceisfunctional,butdonotensurespecificperformancelimits.ElectricalCharacteristicsstateDCandACelectrical
specificationsunderparticulartestconditionswhichensurespecificperformancelimits.Thisassumesthatthedeviceiswithinthe
OperatingRatings.Specificationsarenotensuredforparameterswherenolimitisgiven,however,thetypicalvalueisagoodindication
ofdeviceperformance.
(2) AllvoltagesaremeasuredwithrespecttosupplyGND,unlessotherwisespecified.
(3) Typicalsaremeasuredat25°Candrepresenttheparametricnorm.
(4) LimitsareensuredtoAOQL(AverageOutgoingQualityLevel).
(5) ACElectricalTest;refertoTestCircuit#2.
(6) Thefeedbackcompensationnetworklimitsthebandwidthoftheclosed-loopresponseandsotheslewratewillbereducedduetothe
highfrequencyroll-off.Withoutfeedbackcompensation,theslewrateistypically16V/μs.
(7) DCElectricalTest;refertoTestCircuit#1.
(8) Theoutputdropoutvoltageisthesupplyvoltageminustheclippingvoltage.RefertotheClippingVoltagevs.SupplyVoltagegraphin
theTypicalPerformanceCharacteristicssection.
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Test Circuit #1
(DCElectricalTestCircuit)
Figure3.
Test Circuit #2
(ACElectricalTestCircuit)
Figure4.
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Single Supply Application Circuit
*Optionalcomponentsdependentuponspecificdesignrequirements.RefertotheExternalComponentsDescription
sectionforacomponentfunctiondescription.
Figure5. TypicalSingleSupplyAudioAmplifierApplicationCircuit
External Components Description
(Figure1andFigure5)
Components FunctionalDescription
1. R Actsasavolumecontrolbysettingthevoltagelevelallowedtotheamplifier'sinputterminals.
IN
2. R ProvidesDCvoltagebiasingforthesinglesupplyoperationandbiascurrentforthepositiveinputterminal.
A
3. C Providesbiasfiltering.
A
4. C ProvidesACcouplingattheinputandoutputoftheamplifierforsinglesupplyoperation.
5. R Preventscurrentsfromenteringtheamplifier'snon-invertinginputwhichmaybepassedthroughtotheloaduponpower-
B
downofthesystemduetothelowinputimpedanceofthecircuitrywhentheunder-voltagecircuitryisoff.This
phenomenonoccurswhenthesupplyvoltagesarebelow1.5V.
6. C (1) Reducesthegain(bandwidthoftheamplifier)athighfrequenciestoavoidquasi-saturationoscillationsoftheoutput
C
transistor.Thecapacitoralsosuppressesexternalelectromagneticswitchingnoisecreatedfromfluorescentlamps.
7. Ri InvertinginputresistancetoprovideACGaininconjunctionwithR .
f1
8. Ci(1) Feedbackcapacitor.EnsuresunitygainatDC.Alsoalowfrequencypole(highpassroll-off)at:
f =1/(2πRiCi).
c
9. R FeedbackresistancetoprovideACGaininconjunctionwithRi.
f1
10. R (1) AthigherfrequenciesfeedbackresistanceworkswithC toprovidelowerACGaininconjunctionwithR andRi.Ahigh
f2 f f1
frequencypole(lowpassroll-off)existsat:
f =[R R ](s+1/R C]/[(R +R )(s+1/C (R +R ))].
c f1 f2 f2 f f1 f2 f f1 f2
11. C(1) CompensationcapacitorthatworkswithR andR toreducetheACGainathigherfrequencies.
f f1 f2
12. R (1) WorkswithC tostabilizetheoutputstagebycreatingapolethateliminateshighfrequencyoscillations.
SN SN
13. C (1) WorkswithR tostabilizetheoutputstagebycreatingapolethateliminateshighfrequencyoscillations. f =1/(2πR
SN SN c SN
C ).
SN
14. L(1) ProvideshighimpedanceathighfrequenciessothatRmaydecoupleahighlycapacitiveloadandreducetheQofthe
seriesresonantcircuitduetocapacitiveload.AlsoprovidesalowimpedanceatlowfrequenciestoshortoutRandpass
audiosignalstotheload.
15. R(1)
16. C Providespowersupplyfilteringandbypassing.
S
(1) Optionalcomponentsdependentuponspecificdesignrequirements.RefertotheApplicationInformationsectionformoreinformation.
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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 described above are applicable in both single and split
voltagesupplyconfigurations.
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Typical Performance Characteristics
SPiKe
SafeArea ProtectionResponse
Figure6. Figure7.
SupplyCurrentvs
SupplyVoltage PulseThermalResistance
Figure8. Figure9.
SupplyCurrentvs
PulseThermalResistance OutputVoltage
Figure10. Figure11.
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Typical Performance Characteristics (continued)
PulsePowerLimit PulsePowerLimit
Figure12. Figure13.
SupplyCurrentvs ClippingVoltage
CaseTemperature vsSupplyVoltage
Figure14. Figure15.
InputBiasCurrentvs
CaseTemperature PeakOutputCurrent
Figure16. Figure17.
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