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短的-circuitprotectionandautomaticrecoveryfeature
THERMALPROTECTION
打印-circuitboard(pcb)布局
TPA3008D2
SLOS435A–MAY2004–REVISEDJULY2004
thetpa3008d2hasshort-circuitprotectioncircuitryontheoutputsthatpreventsdamagetothedeviceduring
输出-至-outputshorts,输出-至-gndshorts,andoutput-至-v
CC
shorts.whenashortcircuitisdetectedonthe
输出,thepartimmediatelydisablestheoutputdrive.thisisalatchedfaultandmustberesetbycyclingthe
voltageontheshutdownpintoalogiclowandbacktothelogichighstatefornormaloperation.thisclears
theshort-circuitflagandallowsfornormaloperationiftheshortwasremoved.iftheshortwasnotremoved,这
protectioncircuitryagainactivates.
thefaultterminalcanbeusedforautomaticrecoveryfromashort-circuitevent,orusedtomonitorthestatus
withanexternalgpio.
ThermalprotectionontheTPA3008D2preventsdamagetothedevicewhentheinternaldietemperature
exceeds150
°
c.thereisa
±
15degreetoleranceonthistrippointfromdevicetodevice.oncethedie
temperatureexceedsthethermalsetpoint,thedeviceentersintotheshutdownstateandtheoutputsare
无能.thisisnotalatchedfault.thethermalfaultisclearedoncethetemperatureofthedieisreducedby
20
°
c.thedevicebeginsnormaloperationatthispointwithnoexternalsysteminteraction.
becausethetpa3008d2isaclass-damplifierthatswitchesatahighfrequency,thelayoutoftheprinted-电路
板(pcb)shouldbeoptimizedaccordingtothefollowingguidelinesforthebestpossibleperformance.
•
decouplingcapacitors—thehigh-frequency0.1-µfdecouplingcapacitorsshouldbeplacedasclosetothe
pvcc(pins14,15,22,23,38,39,46,and47)andav
CC
(pin33)terminalsaspossible.thev2p5(pin4)
电容,av
DD
(pin29)电容,andvclamp(pins25and36)capacitorshouldalsobeplacedasclose
tothedeviceaspossible.大(10µforgreater)bulkpowersupplydecouplingcapacitorsshouldbe
placednearthetpa3008d2onthepvccl,pvccr,andav
CC
terminals.
•
Grounding—TheAV
CC
(pin33)decouplingcapacitor,av
DD
(pin29)电容,v2p5(pin4)电容,cosc
(pin28)电容,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
可靠性.thedimensionsofthepowerpadthermallandshouldbe5mmby5mm(197milsby197mils).
thepowerpadsizemeasures4,55x4,55mm.fourrowsofsolidvias(fourviasperrow,0,3302mmor13
milsdiameter)shouldbeequallyspacedunderneaththethermalland.theviasshouldconnecttoasolid
copperplane,eitheronaninternallayeroronthebottomlayerofthepcb.theviasmustbesolidvias,不
thermalrelieforwebbedvias.foradditionalinformation,seethepowerpadthermallyenhancedpackage
applicationnote,(slma002).
foranexamplelayout,seethetpa3008d2evaluationmodule(tpa3008d2evm)usermanual,(slou165).
BoththeEVMusermanualandthePowerPADapplicationnoteareavailableontheTIWebsiteat
http://www.德州仪器.com.
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