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ReverseCurrent
PowerDissipation
ThermalProtection
P
D
(v
在
V
输出
)
I
输出
(6)
PackageMounting
TPS736xx
SBVS038K–SEPTEMBER2003–REVISEDSEPTEMBER2005
expectedambienttemperatureandworst-caseload.
TheNMOSpasselementoftheTPS736xxprovidesTheinternalprotectioncircuitryoftheTPS736xxhas
inherentprotectionagainstcurrentflowfromthebeendesignedtoprotectagainstoverloadconditions.
outputoftheregulatortotheinputwhenthegateofitwasnotintendedtoreplaceproperheatsinking.
thepassdeviceispulledlow.toensurethatallcontinuouslyrunningthetps736xxintothermal
chargeisremovedfromthegateofthepasselement,shutdownwilldegradereliability.
theenablepinmustbedrivenlowbeforetheinput
voltageisremoved.ifthisisnotdone,thepass
elementmaybeleftonduetostoredchargeonthe
Theabilitytoremoveheatfromthedieisdifferentfor
门.
eachpackagetype,presentingdifferentconsider-
aftertheenablepinisdrivenlow,nobiasvoltageis
ationsinthepcblayout.thepcbareaaroundthe
neededonanypinforreversecurrentblocking.便条
devicethatisfreeofothercomponentsmovesthe
thatreversecurrentisspecifiedasthecurrentflowing
heatfromthedevicetotheambientair.效能
outoftheINpinduetovoltageappliedontheOUT
dataforJEDEClowandhighKboardsareshownin
管脚.therewillbeadditionalcurrentflowingintothe
thepowerdissipationratingstable.usingheavier
OUTpinduetothe80k
Ω
internalresistordividerto
copperwillincreasetheeffectivenessinremoving
地面(看Figure1和Figure2).
heatfromthedevice.theadditionofplated
通过-holestoheat-dissipatinglayerswillalsoim-
forthetps73601,reversecurrentmayflowwhen
provetheheat-sinkeffectiveness.
V
FB
ismorethan1.0vabovev
在
.
Powerdissipationdependsoninputvoltageandload
情况.powerdissipationisequaltotheproduct
oftheoutputcurrenttimesthevoltagedropacross
Thermalprotectiondisablestheoutputwhenthe
theoutputpasselement(v
在
toV
输出
):
junctiontemperaturerisestoapproximately160°c,
allowingthedevicetocool.whenthejunctiontem-
peraturecoolstoapproximately140°c,theoutput
Powerdissipationcanbeminimizedbyusingthe
circuitryisagainenabled.dependingonpowerdissi-
lowestpossibleinputvoltagenecessarytoassurethe
pation,thermalresistance,andambienttemperature,
requiredoutputvoltage.
thethermalprotectioncircuitmaycycleonandoff.
thislimitsthedissipationoftheregulator,protecting
itfromdamageduetooverheating.
Anytendencytoactivatethethermalprotectioncircuit
Solderpadfootprintrecommendationsforthe
indicatesexcessivepowerdissipationoraninad-
TPS736xxarepresentedinApplicationBulletin
equateheatsink.forreliableoperation,接合面
solderpadrecommendationsforsurface-mountde-
temperatureshouldbelimitedto125°cmaximum.至
vices
(ab-132),availablefromthetexasinstruments
estimatethemarginofsafetyinacompletedesign
websiteatwww.德州仪器.com.
(includingheatsink),increasetheambienttempera-
tureuntilthethermalprotectionistriggered;使用
worst-caseloadsandsignalconditions.forgood
可靠性,thermalprotectionshouldtriggeratleast
35°cabovethemaximumexpectedambientcon-
ditionofyourapplication.thisproducesaworst-情况
junctiontemperatureof125°Catthehighest
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