www.德州仪器.com
1
10
01020
− 电源 消耗 限制 − w
P
D
R
θ
SA
− 散热器 热的 阻抗 −
°
c/w
非 散热器
T
一个
= 55
°
C
自然的 convection
空气 流动 = 150 lfm
空气 流动 = 250 lfm
空气 流动 = 500 lfm
至-263powerdissipation
P
D
最大值
(
3.3 – 2.5
)
V x 3 一个
2.4 W
(7)
R
θ
JA
最大值
(125 – 55)
°
C
2.4 W
29
°
C
W
(8)
tps75801,tps75815
tps75818,tps75825
TPS75833
SLVS330D–JUNE2001–REVISEDMARCH2004
thermalinformation(持续)
figure24.powerdissipationvsheatsinkthermalresistance
theto-263packageprovidesaneffectivemeansofmanagingpowerdissipationinsurface-mountapplications.
theto-263packagedimensionsareprovidedinthe
MechanicalData
sectionattheendofthedatasheet.这
additionofacopperplanedirectlyunderneaththeto-263packageenhancesthethermalperformanceofthe
包装.
toillustrate,thetps75825inato-263packagewaschosen.forthisexample,theaverageinputvoltageis3.3
v,theaverageoutputvoltageis2.5v,theaverageoutputcurrentis3a,theambienttemperature55
°
c,theair
flowis150lfm,andtheoperatingenvironmentisthesameasdocumentedbelow.neglectingthequiescent
电流,themaximumaveragepoweris:
SubstitutingT
J
maxforT
J
intoequation4givesequation8:
fromfigure25,r
Θ
JA
vscopperheatsinkarea,thegroundplaneneedstobe2cm
2
fortheparttodissipate2.4
w.themodeloperatingenvironmentusedinthecomputermodeltoconstructfigure25consistedofastandard
jedechigh-kboard(2s2p)witha1oz.internalcopperplaneandgroundplane.thepackageissolderedtoa
2oz.copperpad.thepadistiedthroughthermalviastothe1oz.groundplane.figure26showsthesideview
oftheoperatingenvironmentusedinthecomputermodel.
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