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AN-1192 Overture Series High Power Solutions (Rev. B)

ApplicationReportSNAA021B September2002 RevisedApril2013AN-1192 Overture ,anddiscussesthreeapplicationcircuits:pa rallel,bridged, :.. 200 +NvsFrequency,RL= 8 , VCC ,BW<80kHz,PO= 1W,56W, +NvsOutputPowerf = 20Hz,1 kHz,20kHz,RL= 8 , VCC= ,BW< +NvsFrequencyRL= 4 , VCC= 35V,BW< 80kHz,PO= 1W,56W, +NvsOutputPowerf = 20Hz,1kHz,20kHz,RL= 4 , VCC= 35V,BW< +NvsFrequencyPO= 1W,56W,200 WRL= 8 , BW< 80kHz,9/16 +NvsOutputPowerf = 20Hz,1kHz,20kHz,RL= 8 , BW< 80kHz,9/16 , September2002 RevisedApril2013AN-1192 Overture SeriesHighPowerSolutionsSubmitDocumentationFeedbackCopyright 2002 2013, 200W,RL= 8 , BW> 500kHz,9/16 (dBV)RL= 8 , BW< 22kHz,9/16 (dBV)RL= 8 , BW< 22kHz,9/16 (dBV)

Thermal Background www.ti.com If the bridged and parallel configurations are combined, the outcome is a very high power amplifier solution that far exceeds the capabilities of one IC alone, while maintaining reasonable power dissipation

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Transcription of AN-1192 Overture Series High Power Solutions (Rev. B)

1 ApplicationReportSNAA021B September2002 RevisedApril2013AN-1192 Overture ,anddiscussesthreeapplicationcircuits:pa rallel,bridged, :.. 200 +NvsFrequency,RL= 8 , VCC ,BW<80kHz,PO= 1W,56W, +NvsOutputPowerf = 20Hz,1 kHz,20kHz,RL= 8 , VCC= ,BW< +NvsFrequencyRL= 4 , VCC= 35V,BW< 80kHz,PO= 1W,56W, +NvsOutputPowerf = 20Hz,1kHz,20kHz,RL= 4 , VCC= 35V,BW< +NvsFrequencyPO= 1W,56W,200 WRL= 8 , BW< 80kHz,9/16 +NvsOutputPowerf = 20Hz,1kHz,20kHz,RL= 8 , BW< 80kHz,9/16 , September2002 RevisedApril2013AN-1192 Overture SeriesHighPowerSolutionsSubmitDocumentationFeedbackCopyright 2002 2013, 200W,RL= 8 , BW> 500kHz,9/16 (dBV)RL= 8 , BW< 22kHz,9/16 (dBV)RL= 8 , BW< 22kHz,9/16 (dBV)

2 RL= 8 , BW< 22kHz,9/16 SeriesHighPowerSolutionsSNAA021B September2002 RevisedApril2013 SubmitDocumentationFeedbackCopyright 2002 2013, broadportfolioofmonolithicpowerintegrate dcircuitscoveringpowerlevelsfroma ,however,forreallyhighpowerapplications, speciallydesigned. However,thereis a pricetobepaidfordiscreteamplifierdesigns ;theyarecomplex,difficulttodesign,requir emanycomponents, numberofthesetypesofcircuits,buttheytoop ossessallofthesameflawsasdiscretecircuit s,includinga toprovidesimplehigh-powersolutionsthatar econservativelydesigned, ,butnotunique,applicationcircuitsthatpro videoutputpowerof100W,200W, ,bridged, , ,thesecircuitsinherentlypossessthefullpr otectionofeachindividualICthatis ,thesecircuitsarewellknownandhavebeenin (100 WBridgedCircuit),PA100(100 Wparallelcircuit),andtheBPA200(200 WBridged/ParallelCircuit)

3 Arehighpowersolutionsthatcanbeusedin manyapplications,buttheyareprimarilytarg etedforhometheateramplifierapplicationss uchaspoweredsubwoofers,self-poweredspeak ers, ,theyalsoconsumefourtimesmorepowerthana ,it is feasibletoconservativelydesigna100 Wbridgedamplifiersolution, designedtodrivean8 ,whichis itsabilitytodividetotalpowerdissipationb etweenICs,sinceeachamplifieris thatunlikethebridgedesign, ,anynumberofICscanbeusedin ,usingfourICstodrivea 1 loadmeansthateachICdissipates1 ,theloadtoeachIClookslikea 4 load(NumberOfICsin Parallel* LoadImpedance= LoadImpedanceseenbyeachindividualIC.) (<8 ), theparallelcircuitis a September2002 RevisedApril2013AN-1192 Overture SeriesHighPowerSolutionsSubmitDocumentationFeedbackCopyright 2002 2013, thebridgedandparallelconfigurationsarecombined,theoutcomeis a veryhighpoweramplifiersolutionthatfarexceedsthecapabilitiesofoneICalone, ,whiletheICsrunata normaltemperature, shownin (>200W)intoloadswithanimpedancefrom4 to8.

4 Forloadslessthan4 , thefollowingsectionswillexemplifythatthe parallel,bridged, , ,theprotectionmechanismswithintheIC,whic harenoteasilydesigneddiscretely, ,asalways, ,thethermaldesignis equallycriticalwithOverture designbypowerdissipation is ,BR100,andBPA200schematicsandtestresults exemplifywhatcanbeachievedwithpropercomp onentselection,thermaldesign, , monolithicICin itsintendedapplicationandwithinitsspecif iedcapabilities,thethermaldesignis usedbeyondis capabilities,asin highpowercircuits, ,thedesignermustunderstandtheIC'spowerdi ssipationcapabilitiesbeforeusingtheICin a powerICareeitherspecifiedin 125W, derivedfromtheIC'sjunction-to-casetherma lresistance, JC= 1 C/W,themaximumjunctiontemperature,TJ= 150 C,andtheambientair,TA=25 thedatasheet, (TSD).

5 TherealproblemforOverture ICs,however,comesfromthesensitivityofthe outputstage'suniqueSPiKe Protectionwhichdynamicallymonitorstheout puttransistor' enabledatTJ=150 C,SPiKe circuitryis enabledatTJ= 250 C forinstantaneouspowerspikesin ,SPiKe circuitrybecomesevenmoresensitivecausing it toturnonbeforethe125 Wlimitis conjunctionwiththeSPiKe , ,whatis thepowerdissipationlimitfortheICsuchthat SPiKe circuitryis notenabled?Knowingthepowerdissipationlim itandkeepingthecasetemperatureoftheICasc oolaspossiblewillexpandtheoutputpowercap abilitywithoutactivatingSPiKe SeriesHighPowerSolutionsSNAA021B September2002 RevisedApril2013 SubmitDocumentationFeedbackCopyright 2002 2013, toanalyzetheoutputpowerspecificationin ,therearetwooutputpowerspecificationassu rances:60W(min)intoa 4 loadusing 28 Vsuppliesand50W(typ)intoan8 loadfrom ,resultsin.

6 Pdmax= VCCtot2/2 2RL(1)Non-IsolatedLM3886 28V,RL= 4 (2)Pdmax= VCCtot2/2 2RL= ( 28V)2/2 2(4 ) = (3) 35V,RL= 8 (4)Pdmax= VCCtot2/2 2RL= ( 35V)2/2 2(8 ) = (5)TheseresultsshowthattheICcanhandlea maximumof 40 WofcontinuouspowerdissipationwithoutSPiK e ICsaswell,liketheLM3876T,whichis shouldbenotedthattheresultsshownaboveare forthenon-isolatedpowerpackage,wheretheb ackofthepackageis tiedtothesiliconsubstrate,or C/Wforthenon-isolatedversionto 2 beingtestedattheworstcasepowerdissipatio npointfora ,theno-loadvoltagewillbesomewhathigher(1 5% 35%) audio application,theaveragemusicpowerdissipat ionis muchlessthanthemaximumpowerdissipationcr eatedbya , ,whenyouputthesetwopointstogether,theymo stlycancelout, ,whendoingthethermalportionofthedesign, bridgedamplifiersolution,thesingle-ended Pdmaxequationisusedasa bridgedamplifiersolutionrequirestwoampli fiersandeachamplifierwillsee1 and1/2intothesingle-endedPdmaxequationre sultsin thetotalPdmaxequationfora 2*[VCCtot2/2 2(/ RL)] = 4*(VCCtot2/2 2RL)(6)

7 5 SNAA021B September2002 RevisedApril2013AN-1192 Overture SeriesHighPowerSolutionsSubmitDocumentat ionFeedbackCopyright 2002 2013, a dualamplifierICisused,thenthetotalPdmaxw ouldneedtobedissipatedin ,if twoindividualICsareused,thenthetotalpowe rdissipationis :VCC= 28V,RL= 4 (7)Pdmax= 4 VCCtot2/2 2RL= 4( 28V)2/2 2(4 ) = (8)Pdmax= (9)Pdmax/IC= (10)Therefore,usinga bridgedconfiguration,Vccwouldhavetobeequ alto 20 VtokeeptheIC'spowerdissipationwithin40W/ ICwhendrivinga 4 load!Thisequatestoabout110 Wofoutputpowerin bridged-modedrivinga 4 load,andusingthesamebridgedpdmaxequation andamaximumof40W/ICofpowerdissipation,th esupplyvoltageswouldhavetobe parallelamplifiersolutionthesingle-ended Pdmaxequationisusedasa parallelsolutionhastheloadconnectedthesa meassingle-endedsolution(onesidetoGND)ju stmoredevicesdrivingtheload, VCCtot2/2 2RL(11)Theadvantageoftheparallelsolution is totalPdmaxis dividedequallyamongeachoftheamplifiersin , s Overturepoweramplifierseriesamplifierswi llgivethemostoutputpowerandpowerdissipat ionwillbekeptwithinlimitswheneachamplifi erseesa loadimpedanceof4 8.

8 Eachamplifierin a parallelsolutionseesa loadimpedanceequaltothetotalloadimpedanc e* 4 solutionusingtwoamplifierswillresultin eachamplifierseeingan8 s LM3886in a two-deviceparallelsolutiondrivinga 4 2 solutionusingtwoLM3886 ICswillresultin eachICseeinga 4 6 bridgemodethenadditionalamplifiersin paralleltotheamplifiersoneachsideofthebr idge(seeFigure13andFigure17). TofindtheequationforPdmaxBPAthePdmaxBTLe quationis usedasa ,addingdevicesinparalleldoesnotchangethe PdmaxequationsothetotalPdmaxfora bridged/parallelsolutionis thesameasfora 4*(VCCtot2/2 2RL)(12)Thistotalpowerdissipationis dividedequallyamongalloftheamplifiersin a bridged/parallelcircuitthePdmaxBPAequati onis usedasa factorof1/2giving:PdmaxBPA(IC)= 4*(VCCtot2/2 2RL) * ( ) = 2*(VCCtot2/2 2RL)(13)6AN-1192 Overture SeriesHighPowerSolutionsSNAA021B September2002 RevisedApril2013 SubmitDocumentationFeedbackCopyright 2002 2013, paralleltoeachsideofthebridgeasshownin Figure13andFigure17dividesthepowerbetwee nthetwoamplifiersin.

9 PdmaxBPA(IC)= 2*(VCCtot2/2 2RL) * ( ) = VCCtot2/2 2RL(14)whichis moredevicesareaddedin paralleltoeachsideofthebridgetheninstead ofa factorof a factorof1/(NumberofAmplifiers)wouldbeuse din (IC)equationis tousethesingled-endedPdmaxequationanddet erminetheloadimpedanceseenbyeachamplifie rin ,a bridgecircuitmeanseachsideofthebridgewil lsee1/2theloadimpedanceanda parallelcircuitresultsin eachamplifierseeinga loadimpedanceequaltotheload* thenumberofamplifiersin generalequationforPdmaxBPA(IC).PdmaxBPA( IC)= VCCtot2/2 2[(#ofampsin parallel/2)*RL](15)Where# ofampsin parallelis thenumberofamplifiersin paralleloneachsideofthebridgeandnottheto talnumberofamplifiersin ,if a 4 loadis usedandthenumberofamplifiersinparallelis threepersideofthebridge(sixamplifierstot al)thentheloadseenbyeachamplifieris:3/2* 4 = 6.

10 'sportfolioofproductsandthecapabilitieso fthebridged/parallelcircuit,thebridgedso lutionis applicablefora a morerobustdesignthanthebridgedcircuit, ,Figure6, 4 6 8 16 BR100NR(1) 20V 24V 28V 37 VPA100 28V 37V 37 VNA(2)NA(2)BPA200 20V 28V 32V 37 VNA(2)(1)NR= NotRecommended(2)NA= NoAdvantagecomparedtosingle-endedorother configurationsInadditiontobetterheatsink ing,theapplicationofa smallfancansubstantiallyincreasetheIC' notknown,itsairflowseemedtobeconsistentw itha summarizedbelowin Table2. Thedatashownbelowshouldonlybeusedasa , ,labtestingis (NoFan)(WithFan)LM3886T40W60 WLM3886TF30W45W7 SNAA021B September2002 RevisedApril2013AN-1192 Overture SeriesHighPowerSolutionsSubmitDocumentat ionFeedbackCopyright 2002 2013,TexasInstrumentsIncorporatedBR100 Table2 wasobtainedbyusingthebridged/parallelcon figurationandthefollowingconditions:Thes ystemwaswarmedupforanhourusinga powerdissipationof30 Wperdevicewitha 4 ,thenthesupplyvoltageswereincrementedwhi leinsuringthatSPiKe protectionorthermalshutdownwasenabled,pr ovidingtheIC' highx longx thickwith(10) deepfinsandtheheatsinkis blackanodized.


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