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APPLICATIONINFORMATION
InputandOutputCapacitorRequirements
OutputNoise
TPS736xx
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)
TPS736xx
GNDEN FB
在 输出
V
在
V
输出
V
输出
=
×
1.204
(r
1
+ R
2
)
R
1
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
和 改进
瞬时 回馈.
V
N
(
V
RMS
)
8.5
V
RMS
V
V
输出
(v)
(3)
TPS736xx
SBVS038K–SEPTEMBER2003–REVISEDSEPTEMBER2005
TheTPS736xxbelongstoafamilyofnewgeneration
LDOregulatorsthatuseanNMOSpasstransistorto
achieveultra-低-dropoutperformance,reversecur-
althoughaninputcapacitorisnotrequiredforstab-
rentblockage,andfreedomfromoutputcapacitor
ility,itisgoodanalogdesignpracticetoconnecta
constraints.thesefeatures,combinedwithlownoise
0.1µfto1µflowesrcapacitoracrosstheinput
andanenableinput,makethetps736xxidealfor
supplyneartheregulator.thiswillcounteractreac-
portableapplications.thisregulatorfamilyoffersa
tiveinputsourcesandimprovestransientresponse,
wideselectionoffixedoutputvoltageversionsandan
noiserejection,andripplerejection.ahigher-值
adjustableoutputversion.allversionshavethermal
capacitormaybenecessaryiflarge,fastrise-时间
andover-currentprotection,includingfoldbackcur-
loadtransientsareanticipatedorthedeviceislo-
rentlimit.
catedseveralinchesfromthepowersource.
Figure31showsthebasiccircuitconnectionsforthe
TheTPS736xxdoesnotrequireanoutputcapacitor
fixedvoltagemodels.Figure32givestheconnections
forstabilityandhasmaximumphasemarginwithno
fortheadjustableoutputversion(tps73601).r
1
和
电容.itisdesignedtobestableforallavailable
R
2
canbecalculatedforanyoutputvoltageusingthe
typesandvaluesofcapacitors.inapplicationswhere
formulainFigure32.sampleresistorvaluesfor
V
在
–V
输出
<0.5vandmultiplelowesrcapacitors
commonoutputvoltagesareshowninFigure2.为
areinparallel,ringingmayoccurwhentheproductof
bestaccuracy,maketheparallelcombinationofr
1
C
输出
andtotalESRdropsbelow50n
Ω
f.totalesr
andR
2
approximately19k
Ω
.
includesallparasiticresistances,includingcapacitor
esrandboard,插座,andsolderjointresistance.
inmostapplications,thesumofcapacitoresrand
traceresistancewillmeetthisrequirement.
aprecisionband-gapreferenceisusedtogenerate
theinternalreferencevoltage,v
REF
.thisreferenceis
thedominantnoisesourcewithintheTPS736xxand
itgeneratesapproximately32µV
RMS
(10hzto
100khz)atthereferenceoutput(nr).theregulator
controlloopgainsupthereferencenoisewiththe
samegainasthereferencevoltage,sothatthenoise
voltageoftheregulatorisapproximatelygivenby:
figure31.typicalapplicationcircuitfor
fixed-voltageversions
SincethevalueofV
REF
is1.2v,thisrelationship
reducesto:
forthecaseofnoC
NR
.
Aninternal27k
Ω
resistorinserieswiththenoise
reductionpin(nr)formsalow-passfilterforthe
voltagereferencewhenanexternalnoisereduction
电容,c
NR
,isconnectedfromnrtoground.为
C
NR
=10nf,thetotalnoiseinthe10hzto100khz
bandwidthisreducedbyafactorof~3.2,givingthe
approximaterelationship:
figure32.typicalapplicationcircuitfor
可调整的-voltageversions
forC
NR
=10nf.
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