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加载 步伐
补偿
VIN
竞赛
R
C
15 k
Ω
C
C
1 nf
f
z
1
2
Cc
Rc
TPS65100
TPS65105
SLVS496B–SEPTEMBER2003–REVISEDMARCH2004
figure16.loadstepcausedbyatoolargefeedforwardcapacitorvalue
theregulatorloopcanbecompensatedbyadjustingtheexternalcomponentsconnectedtothecomppin.这
comppinisconnectedtotheoutputoftheinternaltransconductanceerroramplifier.atypicalcompensation
schemeisshowninfigure17.
figure17.compensationnetwork
ThecompensationcapacitorC
c
adjuststhelowfrequencygainandtheresistorvalueadjuststhehighfrequency
增益.theformulabelowcalculatesatwhatfrequencytheresistorincreasesthehighfrequencygain.
lowerinputvoltagesrequireahighergainandthereforealowercompensationcapacitorvalue.agoodstartis
C
c
=1nffora3.3-vinputandc
c
=2.2nffora5-vinput.ifthedeviceoperatesovertheentireinputvoltage
rangefrom2.7vto5.8v,alargecompensationcapacitorupto10nfisrecommended.figure18showsthe
loadtransientwithalargercompensationcapacitor,andfigure19showsasmallercompensationcapacitor.
figure18.c
c
=4.7nf
16