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APPLICATIONINFORMATION
INPUTANDOUTPUTCAPACITOR
OUTPUTNOISE
TPS731xx
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 输出 电容.
将 改进 加载 瞬时,
噪音, 或者 psrr.
Optional 绕过
电容 至 减少
输出 噪音.
V
N
32
V
RMS
(r
1
R
2
)
R
2
32
V
RMS
V
输出
V
REF
(1)
V
N
(
V
RMS
)
27
V
RMS
V
V
输出
(v)
(2)
TPS731xx
GNDEN
FB
在 输出
V
在
V
输出
V
输出
=
×
1.204
(r
1
+ R
2
)
R
1
C
FB
R
2
Optional 输入 电容.
将 改进 源
阻抗, 噪音, 或者 psrr.
Optional 输出 电容.
将 改进 加载 瞬时,
噪音, 或者 psrr.
Optional 电容
减少 输出 噪音.
R
2
V
N
(
V
RMS
)
8.5
V
RMS
V
V
输出
(v)
(3)
tps73101,tps73115,tps73118
tps73125,tps73130,tps73132
tps73133,tps73150
SBVS034E–SEPTEMBER2003–REVISEDSEPTEMBER2004
TheTPS731xxbelongstoafamilyofnewgeneration
LDOregulatorsthatuseanNMOSpasstransistorto
(所需的)东西
achieveultra-低-dropoutperformance,reversecur-
rentblockage,andfreedomfromoutputcapacitor
althoughaninputcapacitorisnotrequiredforstab-
constraints.thesefeatures,combinedwithlownoise
ility,itisgoodanalogdesignpracticetoconnecta
andanenableinput,makethetps731xxidealfor
0.1µfto1µflowesrcapacitoracrosstheinput
portableapplications.thisregulatorfamilyoffersa
supplyneartheregulator.thiscounteractsreactive
wideselectionoffixedoutputvoltageversionsandan
inputsourcesandimprovestransientresponse,噪音
adjustableoutputversion.allversionshavethermal
拒绝,andripplerejection.ahigher-valuecapaci-
andover-currentprotection,includingfoldbackcur-
tormaybenecessaryiflarge,fastrise-timeload
rentlimit.
transientsareanticipatedorthedeviceislocated
severalinchesfromthepowersource.
Figure31showsthebasiccircuitconnectionsforthe
fixedvoltagemodels.figure32givestheconnections
TheTPS731xxdoesnotrequireanoutputcapacitor
fortheadjustableoutputversion(tps73101).
forstabilityandhasmaximumphasemarginwithno
电容.itisdesignedtobestableforallavailable
typesandvaluesofcapacitors.inapplicationswhere
V
在
-v
输出
<0.5vandmultiplelowesrcapacitors
areinparallel,ringingmayoccurwhentheproductof
C
输出
andtotalESRdropsbelow50n
Ω
f.totalesr
includesallparasiticresistances,includingcapacitor
esrandboard,插座,andsolderjointresistance.
inmostapplications,thesumofcapacitoresrand
traceresistancewillmeetthisrequirement.
aprecisionband-gapreferenceisusedtogenerate
theinternalreferencevoltage,v
REF
.thisreferenceis
thedominantnoisesourcewithintheTPS731xxand
figure31.typicalapplicationcircuitfor
itgeneratesapproximately32µvrms(10hzto
fixed-voltageversions
100khz)atthereferenceoutput(nr).theregulator
controlloopgainsupthereferencenoisewiththe
samegainasthereferencevoltage,sothatthenoise
voltageoftheregulatorisapproximatelygivenby:
SincethevalueofV
REF
is1.2v,thisrelationship
reducesto:
forthecaseofnoC
NR
.
Aninternal27k
Ω
resistorinserieswiththenoise
figure32.typicalapplicationcircuitfor
reductionpin(nr)formsalow-passfilterforthe
可调整的-voltageversions
voltagereferencewhenanexternalnoisereduction
电容,c
NR
,isconnectedfromnrtoground.为
R
1
andR
2
canbecalculatedforanyoutputvoltage
C
NR
=10nf,thetotalnoiseinthe10hzto100khz
usingtheformulashowninfigure32.samplere-
bandwidthisreducedbyafactorof~3.2,givingthe
sistorvaluesforcommonoutputvoltagesareshown
approximaterelationship:
infigure2.forbestaccuracy,maketheparallel
combinationofR
1
andR
2
approximately19k
Ω
.
forC
NR
=10nf.
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