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− 最大 接合面 temperature − 125
T
JM
C
°
1
2
3
4
5
0.1 1 10 100
− 最大 电源 消耗 − w
P
D
铜 散热器 范围 − cm
2
T
一个
= 55
°
C
非 空气 流动
150 lfm
250 lfm
SOT223PowerDissipation
P
D
最大值
(
3.3
2.5
)
V x 1 一个
800 mW
(9)
R
θ
JA
最大值
(125
55)
°
C
800 mW
87.5
°
C
W
(10)
TPS72501
tps72515,tps72516
tps72518,tps72525
SLVS341D–MAY2002–REVISEDMARCH2004
thermalinformation(持续)
fromthedatainfigure23andrearrangingequation6,themaximumpowerdissipationforadifferentground
planeareaandaspecificambienttemperaturecanbecomputed.
figure23.maximumpowerdissipationvscopperheatsinkarea
thesot223packageprovidesaneffectivemeansofmanagingpowerdissipationinsurfacemountapplications.
TheSOT223packagedimensionsareprovidedinthe
MechanicalData
sectionattheendofthedatasheet.这
additionofacopperplanedirectlyunderneaththeSOT223packageenhancesthethermalperformanceofthe
包装.
toillustrate,thetps72525inasot223packagewaschosen.forthisexample,theaverageinputvoltageis
3.3v,theoutputvoltageis2.5v,theaverageoutputcurrentis1a,theambienttemperature55
°
c,noairflowis
呈现,andtheoperatingenvironmentisthesameasdocumentedbelow.neglectingthequiescentcurrent,这
maximumaveragepoweris:
SubstitutingT
J
maxforT
J
intoequation6givesequation10:
fromfigure24,r
Θ
JA
vspcbcopperarea,thegroundplaneneedstobe0.55in
2
fortheparttodissipate800
mw.theoperatingenvironmentusedtoconstructfigure24consistedofaboardwith1oz.copperplanes.这
packageissolderedtoa1oz.copperpadonthetopoftheboard.thepadistiedthroughthermalviastothe1
oz.groundplane.
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