www.德州仪器.com
APPLICATIONINFORMATION
TPS799xx
GNDEN NR
在 输出
V
在
V
输出
Optional 输入 电容.
将 改进 源
阻抗, 噪音, 或者 psrr.
Optional 绕过 电容
至 减少 输出 噪音
和 增加 psrr.
2.2
µ
F
陶瓷的
V
EN
TPS799xx
GNDEN
FB
在 输出
V
在
V
输出
R
1
C
FB
R
2
Optional 输入 电容.
将 改进 源
阻抗, 噪音, 或者 psrr.
V
输出
=
×
1.193
(r
1
+ R
2
)
R
2
V
EN
2.2
µ
F
陶瓷的
InputandOutputCapacitorRequirements
feedbackcapacitorrequirements(tps79901only)
tps79901,tps79915,tps79916,tps79918
tps79925,tps79927,tps79928,tps799285
tps79929,tps79930,tps79932,tps79933
SBVS056C–JANUARY2005–REVISEDMAY2005
TheTPS799xxfamilyofLDOregulatorscombinesthehighperformancerequiredofmanyRFandprecision
analogapplicationswithultra-lowcurrentconsumption.highpsrrisprovidedbyahighgain,highbandwidth
errorloopwithgoodsupplyrejectionatverylowheadroom(v
在
–V
输出
).fixedvoltageversionsprovideanoise
reductionpintobypassnoisegeneratedbythebandgapreferenceandtoimprovepsrrwhileaquick-开始
circuitfast-chargesthiscapacitoratstartupforquickstartuptimes.thecombinationofhighperformanceandlow
groundcurrentalsomakethetps799xxanexcellentchoiceforportableapplications.allversionshavethermal
andover-currentprotectionandarefullyspecifiedfrom–40°cto+125°c.
Figure28showsthebasiccircuitconnectionsforfixedvoltagemodels.Figure29givestheconnectionsforthe
adjustableoutputversion(tps79901).r
1
andR
2
canbecalculatedforanyoutputvoltageusingtheformulain
Figure29.sampleresistorvaluesforcommonoutputvoltagesareshowninFigure29.
figure28.typicalapplicationcircuitforfigure29.typicalapplicationcircuitfor
FixedVoltageVersionsAdjustableVoltageVersion
althoughaninputcapacitorisnotrequiredforstability,itisgoodanalogdesignpracticetoconnecta0.1µfto
1µflowesrcapacitoracrosstheinputsupplyneartheregulator.thiswillcounteractreactiveinputsourcesand
improvetransientresponse,noiserejection,andripplerejection.ahigher-valuecapacitormaybenecessaryif
大,fastrise-timeloadtransientsareanticipatedorthedeviceislocatedseveralinchesfromthepowersource.
ifsourceimpedanceisnotsufficientlylow,a0.1µfinputcapacitormaybenecessarytoensurestability.
thetps799xxisdesignedtobestablewithstandardceramiccapacitorsofvalues2.2µforlarger.x5rand
x7rtypecapacitorsarebestastheyhaveminimalvariationinvalueandesrovertemperature.maximumesr
shouldbe<1.0
Ω
.
thefeedbackcapacitor,c
FB
,showninFigure29isrequiredforstability.foraparallelcombinationofr
1
andR
2
equalto250k
Ω
,anyvaluefrom3pfto1nfcanbeused.fixedvoltageversionshaveaninternal30pffeedback
capacitorwhichisquick-chargedatstart-向上.theadjustableversiondoesnothavethisquick-chargecircuit,所以
valuesbelow5pfshouldbeusedtoensurefaststartup;valuesabove47pfcanbeusedtoimplementanoutput
voltagesoft-开始.largervaluecapacitorsalsoimprovenoiseslightly.thetps79901isstableinunity-增益
配置(outtiedtofb)withoutc
FB
.
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