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APPLICATIONINFORMATION
ExternalCapacitorRequirements
ProgrammingtheTPS72501AdjustableLDORegulator
V
O
V
ref
1
R1
R2
(1)
R1
V
O
V
ref
1
R2
(2)
V
O
V
I
输出
FB
R1
R2
地
EN
在
TPS72501
1
µ
F
C
o
输出 voltAGE
程序编制 手册
(标准 1% 电阻 values)
程序
电压
r1 (k
Ω
) r2 (k
Ω
)
1.8 v
2.5 v
3.3 v
3.6 v
真实的
电压
56.2
127
196
205
118
121
115
105
1.801
2.500
3.299
3.602
1.22 v
≤
0.4 v
≥
1.3 v
TPS72501
tps72515,tps72516
tps72518,tps72525
SLVS341D–MAY2002–REVISEDMARCH2004
thetps725xxfamilyoflow-落后(ldo)regulatorshasnumerousfeaturesthatmakeitapplicabletoawide
rangeofapplications.thefamilyoperateswithverylowinputvoltage(
≥
1.8v)andlowdropoutvoltage(典型地
200mvatfullload),makingitanefficientstand-alonepowersupplyorpostregulatorforbatteryorswitchmode
powersupplies.boththeactivelowresetand1-aoutputcurrentmakethetps725xxfamilyidealforpowering
processorandfpgasupplies.thetps725xxfamilyalsohaslowoutputnoise(typically150µv
RMS
with10-µf
outputcapacitor),makingitidealforuseintelecomequipment.
a1-µforlargerceramicinputbypasscapacitor,connectedbetweeninandgndandlocatedclosetothe
tps725xx,isrequiredforstability.toimprovetransientresponse,noiserejection,andripplerejection,一个
additional10-µforlarger,lowesrcapacitorisrecommended.ahigher-值,lowesrinputcapacitormaybe
necessaryiflarge,快-上升-timeloadtransientsareanticipatedandthedeviceislocatedseveralinchesfromthe
powersource,especiallyiftheminimuminputvoltageof1.8visused.
althoughanoutputcapacitorisnotrequiredforstability,transientresponseandoutputnoiseareimprovedwitha
10-µfoutputcapacitor.
TheoutputvoltageoftheTPS72501adjustableregulatorisprogrammedusinganexternalresistordivideras
showninfigure19.theoutputvoltageiscalculatedusing:
在哪里:
•
V
FB
=V
REF
=1.22vtypical(seetheelectricalcharacteristicsforv
REF
范围)
resistorsr1andr2shouldbechosenforapproximately10-µadividercurrent.lowervalueresistorsofferno
inherentadvantageandwastemorepower.highervaluesshouldbeavoidedasleakagecurrentsatfbincrease
theoutputvoltageerror.therecommendeddesignprocedureistochooser2=120k
Ω
tosetthedividercurrent
at10µaandthencalculater1using:
figure19.tps72501adjustableldoregulatorprogramming
9
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