www.德州仪器.com
一个
B
C
T
J
一个
R
θ
JC
T
C
B
R
θ
CS
T
一个
C
R
θ
SA
(一个)
(b)
DDPak 包装
sot223 包装
电路 板 铜 范围
B
一个
C
T
J
T
一个
P
D
最大值 x
R
θ
JC
R
θ
CS
R
θ
SA
(4)
T
J
T
一个
P
D
最大值 x R
θ
JA
(5)
R
θ
JA
T
J
–T
一个
P
D
最大值
(6)
DDPAKPowerDissipation
TPS72501
tps72515,tps72516
tps72518,tps72525
SLVS341D–MAY2002–REVISEDMARCH2004
thermalinformation(持续)
figure20.thermalresistances
equation4summarizesthecomputation:
TheR
θ
JC
isspecifictoeachregulatorasdeterminedbyitspackage,引线框架,anddiesizeprovidedinthe
调整器'sdatasheet.ther
θ
SA
isafunctionofthetypeandsizeofheatsink.forexample,
blackbodyradiator
typeheatsinkscanhaveR
θ
CS
valuesrangingfrom5
°
c/wforverylargeheatsinksto50
°
c/wforverysmall
heatsinks.ther
θ
CS
isafunctionofhowthepackageisattachedtotheheatsink.forexample,ifathermal
compoundisusedtoattachaheatsinktoasot223package,r
θ
CS
of1
°
c/wisreasonable.
Evenifnoexternal
blackbodyradiator
typeheatsinkisattachedtothepackage,theboardonwhichthe
regulatorismountedprovidessomeheatsinkingthroughthepinsolderconnections.somepackages,likethe
ddpakandsot223packages,useacopperplaneunderneaththepackageorthecircuitboard'sgroundplane
foradditionalheatsinkingtoimprovetheirthermalperformance.计算机-aidedthermalmodelingcanbeused
tocomputeveryaccurateapproximationsofanintegratedcircuit'sthermalperformanceindifferentoperating
环境(e.g.,differenttypesofcircuitboards,differenttypesandsizesofheatsinks,differentairflows,
等.).usingthesemodels,thethreethermalresistancescanbecombinedintoonethermalresistancebetween
junctionandambient(r
θ
JA
).thisr
θ
JA
isvalidonlyforthespecificoperatingenvironmentusedinthecomputer
模型.
equation4simplifiesintoequation5:
rearrangingequation5givesequation6:
usingequation5andthecomputermodelgeneratedcurvesshowninfigure21andfigure24,adesignercan
quicklycomputetherequiredheatsinkthermalresistance/boardareaforagivenambienttemperature,电源
消耗,andoperatingenvironment.
theddpakpackageprovidesaneffectivemeansofmanagingpowerdissipationinsurfacemountapplications.
TheDDPAKpackagedimensionsareprovidedinthe
MechanicalData
sectionattheendofthedatasheet.这
additionofacopperplanedirectlyunderneaththeDDPAKpackageenhancesthethermalperformanceofthe
包装.
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