www.德州仪器.com
dV
dt
V
输出
C
输出
80k
(
R
1
R
2
)
(5)
REVERSECURRENT
POWERDISSIPATION
THERMALPROTECTION
P
D
(v
在
V
输出
)
I
输出
(6)
PackageMounting
tps73101,tps73115,tps73118
tps73125,tps73130,tps73132
tps73133,tps73150
SBVS034E–SEPTEMBER2003–REVISEDSEPTEMBER2004
(adjustablevoltageversion)可靠性,thermalprotectionshouldtriggeratleast
35
°
cabovethemaximumexpectedambientcon-
ditionofyourapplication.thisproducesaworst-情况
junctiontemperatureof125
°
catthehighestex-
pectedambienttemperatureandworst-caseload.
TheinternalprotectioncircuitryoftheTPS731xxhas
TheNMOSpasselementoftheTPS731xxprovides
beendesignedtoprotectagainstoverloadconditions.
inherentprotectionagainstcurrentflowfromthe
itwasnotintendedtoreplaceproperheatsinking.
outputoftheregulatortotheinputwhenthegateof
ContinuouslyrunningtheTPS731xxintothermal
thepassdeviceispulledlow.toensurethatall
shutdownwilldegradedevicereliability.
chargeisremovedfromthegateofthepasselement,
theenablepinmustbedrivenlowbeforetheinput
voltageisremoved.ifthisisnotdone,thepass
Theabilitytoremoveheatfromthedieisdifferentfor
elementmaybeleftonduetostoredchargeonthe
eachpackagetype,presentingdifferentconsider-
门.
ationsinthepcblayout.thepcbareaaroundthe
aftertheenablepinisdrivenlow,nobiasvoltageis
devicethatisfreeofothercomponentsmovesthe
neededonanypinforreversecurrentblocking.便条
heatfromthedevicetotheambientair.效能
thatreversecurrentisspecifiedasthecurrentflowing
dataforjedeclow-andhigh-kboardsareshownin
outoftheINpinduetovoltageappliedontheOUT
thepowerdissipationratingstable.usingheavier
管脚.therewillbeadditionalcurrentflowingintothe
copperwillincreasetheeffectivenessinremoving
OUTpinduetothe80k
Ω
internalresistordividerto
heatfromthedevice.theadditionofplated
地面(seefigure1andfigure2).
通过-holestoheat-dissipatinglayerswillalsoim-
provetheheat-sinkeffectiveness.
forthetps73101,reversecurrentmayflowwhen
V
FB
ismorethan1.0vabovev
在
.
Powerdissipationdependsoninputvoltageandload
情况.powerdissipationisequaltotheproduct
oftheoutputcurrenttimesthevoltagedropacross
theoutputpasselement(v
在
toV
输出
):
Thermalprotectiondisablestheoutputwhenthe
junctiontemperaturerisestoapproximately160
°
c,
allowingthedevicetocool.whenthejunctiontem-
Powerdissipationcanbeminimizedbyusingthe
peraturecoolstoapproximately140
°
c,theoutput
lowestpossibleinputvoltagenecessarytoassurethe
circuitryisagainenabled.dependingonpowerdissi-
requiredoutputvoltage.
pation,thermalresistance,andambienttemperature,
thethermalprotectioncircuitmaycycleonandoff.
thislimitsthedissipationoftheregulator,protecting
itfromdamageduetooverheating.
Solderpadfootprintrecommendationsforthe
TPS731xxarepresentedinApplicationBulletin
Anytendencytoactivatethethermalprotectioncircuit
solderpadrecommendationsforsurface-mountde-
indicatesexcessivepowerdissipationoraninad-
vices
(ab-132),availablefromthetexasinstruments
equateheatsink.forreliableoperation,junctiontem-
websiteatwww.德州仪器.com.
peratureshouldbelimitedto125
°
cmaximum.至
estimatethemarginofsafetyinacompletedesign
(includingheatsink),increasetheambienttempera-
tureuntilthethermalprotectionistriggered;使用
worst-caseloadsandsignalconditions.forgood
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