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SHORT-CIRCUITPROTECTIONANDAUTOMATICRECOVERYFEATURE
THERMALPROTECTION
PRINTED-CIRCUITBOARD(PCB)LAYOUT
TPA3008D2
SLOS435A–MAY2004–REVISEDJULY2004
TheTPA3008D2hasshort-circuitprotectioncircuitryontheoutputsthatpreventsdamagetothedeviceduring
output-to-outputshorts,output-to-GNDshorts,andoutput-to-V
CC
shorts.Whenashortcircuitisdetectedonthe
outputs,thepartimmediatelydisablestheoutputdrive.Thisisalatchedfaultandmustberesetbycyclingthe
voltageontheSHUTDOWNpintoalogiclowandbacktothelogichighstatefornormaloperation.Thisclears
theshort-circuitflagandallowsfornormaloperationiftheshortwasremoved.Iftheshortwasnotremoved,the
protectioncircuitryagainactivates.
Thefaultterminalcanbeusedforautomaticrecoveryfromashort-circuitevent,orusedtomonitorthestatus
withanexternalGPIO.
ThermalprotectionontheTPA3008D2preventsdamagetothedevicewhentheinternaldietemperature
exceeds150°C.Thereisa±15degreetoleranceonthistrippointfromdevicetodevice.Oncethedie
temperatureexceedsthethermalsetpoint,thedeviceentersintotheshutdownstateandtheoutputsare
disabled.Thisisnotalatchedfault.Thethermalfaultisclearedoncethetemperatureofthedieisreducedby
20°C.Thedevicebeginsnormaloperationatthispointwithnoexternalsysteminteraction.
BecausetheTPA3008D2isaclass-Damplifierthatswitchesatahighfrequency,thelayoutoftheprinted-circuit
board(PCB)shouldbeoptimizedaccordingtothefollowingguidelinesforthebestpossibleperformance.
•Decouplingcapacitors—Thehigh-frequency0.1-µFdecouplingcapacitorsshouldbeplacedasclosetothe
PVCC(pins14,15,22,23,38,39,46,and47)andAV
CC
(pin33)terminalsaspossible.TheV2P5(pin4)
capacitor,AV
DD
(pin29)capacitor,andVCLAMP(pins25and36)capacitorshouldalsobeplacedasclose
tothedeviceaspossible.Large(10µForgreater)bulkpowersupplydecouplingcapacitorsshouldbe
placedneartheTPA3008D2onthePVCCL,PVCCR,andAV
CC
terminals.
•Grounding—TheAV
CC
(pin33)decouplingcapacitor,AV
DD
(pin29)capacitor,V2P5(pin4)capacitor,COSC
(pin28)capacitor,andROSC(pin27)resistorshouldeachbegroundedtoanalogground(AGND,pins26
and30).ThePVCCdecouplingcapacitorsshouldeachbegroundedtopowerground(PGND,pins18,19,
42,and43).AnaloggroundandpowergroundmaybeconnectedatthePowerPAD,whichshouldbeused
asacentralgroundconnectionorstargroundfortheTPA3008D2.Basically,anislandshouldbecreated
withasingleconnectiontoPGNDatthePowerPAD.
•Outputfilter—TheferriteEMIfilter(Figure20)shouldbeplacedasclosetotheoutputterminalsaspossible
forthebestEMIperformance.TheLCfilter(Figure19)shouldbeplacedclosetotheoutputs.Thecapacitors
usedinboththeferriteandLCfiltersshouldbegroundedtopowerground.Ifbothfiltersareused,theLC
filtershouldbeplacedfirst,followingtheoutputs.
•PowerPAD—ThePowerPADmustbesolderedtothePCBforproperthermalperformanceandoptimal
reliability.ThedimensionsofthePowerPADthermallandshouldbe5mmby5mm(197milsby197mils).
ThePowerPADsizemeasures4,55x4,55mm.Fourrowsofsolidvias(fourviasperrow,0,3302mmor13
milsdiameter)shouldbeequallyspacedunderneaththethermalland.Theviasshouldconnecttoasolid
copperplane,eitheronaninternallayeroronthebottomlayerofthePCB.Theviasmustbesolidvias,not
thermalrelieforwebbedvias.Foradditionalinformation,seethePowerPADThermallyEnhancedPackage
applicationnote,(SLMA002).
Foranexamplelayout,seetheTPA3008D2EvaluationModule(TPA3008D2EVM)UserManual,(SLOU165).
BoththeEVMusermanualandthePowerPADapplicationnoteareavailableontheTIWebsiteat
http://www.ti.com.
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