www.德州仪器.com
OvercurrentProtection
outputon/offinhibit
1 = inhibit
地
3.3 v
L
O
一个
D
地
V
I
R
设置
2 k
1%
0.05 w
Q
1
BSS138
C1
PTV12010W
地 调整
V
O
V
I
Inhibit
C2
+
C3
+
追踪
q1vds (5 v/div)
vo (2 v/div)
iin (2一个/div)
horiz 规模: 10 ms/div
PTV12010L
PTV12010W
SLTS234–DECEMBER2004
forprotectionagainstloadfaults,themodulesincorporateoutputovercurrentprotection.applyingaloadthat
exceedstheovercurrentthresholdcausestheregulatedoutputtoshutdown.followingshutdown,amodule
periodicallyattemptstorecoverbyinitiatingasoft-startpowerup.thisisdescribedasa
hiccup
modeof
运作,wherebythemodulecontinuesinacycleofsuccessiveshutdownandpowerupuntiltheloadfaultis
移除.duringthisperiod,theaveragecurrentflowingintothefaultissignificantlyreduced.oncethefaultis
移除,themoduleautomaticallyrecoversandreturnstonormaloperation.
forapplicationsrequiringoutputvoltageon/offcontrol,themodulesincorporateanoutputinhibitcontrolpin.这
inhibitfeaturecanbeusedwhereverthereisarequirementfortheoutputvoltagefromtheregulatortobeturned
止.
Thepowermodulesfunctionnormallywhenthe
Inhibit
inputisleftopen-电路,providingaregulatedoutput
wheneveravalidsourcevoltageisconnectedtoV
I
withrespecttognd.
figure14showsthetypicalapplicationoftheinhibitfunction.notethediscretetransistor(q1).这
Inhibit
输入
hasitsowninternalpullup(seefootnotestoelectricalcharacteristicstable).theinputisnotcompatiblewithttl
logicdevices.anopen-集电级(oropen-流)discretetransistorisrecommendedforcontrol.
figure14.
turningq1onappliesalowvoltagetotheinhibitcontrolpinanddisablestheoutputofthemodule.ifq1isthen
turnedoff,themoduleexecutesasoft-startpower-upsequence.aregulatedoutputvoltageisproducedwithin
25ms.figure15showsthetypicalriseinboththeoutputvoltageandinputcurrent,followingtheturnoffofq1.
theturnoffofq1correspondstotheriseinthewaveform,q1v
DS
.thewaveformsweremeasuredwitha5-一个
constantcurrentload.
figure15.
14