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ProgrammingtheTPS79501AdjustableLDO
C1
(3 x 10
–7
) x (r1
r2)
(r1 x r2)
(3)
V
输出
V
REF
1
R1
R2
(1)
RegulatorProtection
R1
V
输出
V
REF
1
R2
(2)
输出 voltAGE
程序编制 手册
输出
电压
R1 R2 C1
GNDNR
FB
在 输出
EN
V
在
V
输出
R1
C1
R2
1
µ
F
0.01
µ
F
TPS79501
1
µ
F
1.8 v
3.6v
14.0 k
Ω
61.9 k
Ω
30.1 k
Ω
30.1 k
Ω
22 pf
15 pf
tps79501,tps79516
tps79518,tps79525
tps79530,tps79533
SLVS350B–OCTOBER2002–REVISEDOCTOBER2004
调整器
TheoutputvoltageoftheTPS79501adjustable
Thesuggestedvalueofthiscapacitorforseveral
regulatorisprogrammedusinganexternalresistor
resistorratiosisshowninthetablebelow.ifthis
dividerasshowninfigure24.theoutputvoltageis
capacitorisnotused(suchasinaunity-gaincon-
calculatedusingequation1:
figuration)thentheminimumrecommendedoutput
capacitoris2.2µfinsteadof1µf.
在哪里:
thetps795xxpmos-passtransistorhasabuilt-在
•
V
REF
=1.2246vtyp(theinternalreference
backdiodethatconductsreversecurrentwhenthe
电压)
inputvoltagedropsbelowtheoutputvoltage(e.g.,
resistorsr1andr2shouldbechosenforapproxi-
duringpowerdown).currentisconductedfromthe
mately40-µadividercurrent.lowervalueresistors
outputtotheinputandisnotinternallylimited.如果
canbeusedforimprovednoiseperformance,butthe
extendedreversevoltageoperationisanticipated,
devicewastesmorepower.highervaluesshouldbe
externallimitingmightbeappropriate.
避免,asleakagecurrentatfbincreasesthe
TheTPS795xxfeaturesinternalcurrentlimitingand
outputvoltageerror.therecommendeddesignpro-
thermalprotection.duringnormaloperation,这
cedureistochooser2=30.1k
Ω
tosetthedivider
tps795xxlimitsoutputcurrenttoapproximately2.8
currentat40µa,c1=15pfforstability,andthen
一个.whencurrentlimitingengages,theoutputvoltage
calculater1usingequation2:
scalesbacklinearlyuntiltheovercurrentcondition
ends.whilecurrentlimitingisdesignedtoprevent
grossdevicefailure,careshouldbetakennotto
exceedthepowerdissipationratingsofthepackage.
Inordertoimprovethestabilityoftheadjustable
ifthetemperatureofthedeviceexceedsapproxi-
版本,itissuggestedthatasmallcompensation
mately165
°
c,热的-protectioncircuitryshutsit
capacitorbeplacedbetweenoutandfb.这
向下.oncethedevicehascooleddowntobelow
approximatevalueofthiscapacitorcanbecalculated
approximately140
°
c,regulatoroperationresumes.
asequation3:
figure24.tps79501adjustableldoregulatorprogramming
9
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