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APPLICATIONINFORMATION
电源-supplyconsiderations
在
OC1
EN1
OC2
2
8
5
7
0.1
µ
F 22
µ
F
0.1
µ
F 22
µ
F
加载
加载
OUT1
OUT2
电源 供应
2.7 v 至 5.5 v
6
EN2
3
4
地
0.1
µ
F
TPS2062
1
OVERCURRENT
OCRESPONSE
tps2061,tps2062,tps2063
tps2065,tps2066,tps2067
SLVS490B–DECEMBER2003–REVISEDDECEMBER2004
figure25.typicalapplication
a0.01-µfto0.1-µfceramicbypasscapacitorbetweeninandgnd,closetothedevice,isrecommended.
placingahigh-valueelectrolyticcapacitorontheoutputpin(s)isrecommendedwhentheoutputloadisheavy.
thisprecautionreducespower-supplytransientsthatmaycauseringingontheinput.additionally,bypassingthe
outputwitha0.01-µfto0.1-µfceramiccapacitorimprovestheimmunityofthedevicetoshort-circuittransients.
asensefetisemployedtocheckforovercurrentconditions.unlikecurrent-senseresistors,sensefetsdonot
increasetheseriesresistanceofthecurrentpath.whenanovercurrentconditionisdetected,thedevice
maintainsaconstantoutputcurrentandreducestheoutputvoltageaccordingly.completeshutdownoccursonly
ifthefaultispresentlongenoughtoactivatethermallimiting.
threepossibleoverloadconditionscanoccur.inthefirstcondition,theoutputhasbeenshortedbeforethe
deviceisenabledorbeforeV
i(在)
hasbeenapplied(seefigure15).thetps206xsensestheshortand
immediatelyswitchesintoaconstant-currentoutput.
inthesecondcondition,ashortoranoverloadoccurswhilethedeviceisenabled.attheinstanttheoverload
occurs,highcurrentsmayflowforashortperiodoftimebeforethecurrent-limitcircuitcanreact.afterthe
电流-limitcircuithastripped(reachedtheovercurrenttripthreshold),thedeviceswitchesintoconstant-电流
模式.
inthethirdcondition,theloadhasbeengraduallyincreasedbeyondtherecommendedoperatingcurrent.这
currentispermittedtoriseuntilthecurrent-limitthresholdisreachedoruntilthethermallimitofthedeviceis
超过(seefigure18).thetps206xiscapableofdeliveringcurrentuptothecurrent-limitthresholdwithout
damagingthedevice.oncethethresholdhasbeenreached,thedeviceswitchesintoitsconstant-currentmode.
theocxopen-drainoutputisasserted(activelow)whenanovercurrentorovertemperatureshutdowncondition
isencounteredaftera10-msdeglitchtimeout.theoutputremainsasserteduntiltheovercurrentor
overtemperatureconditionisremoved.connectingaheavycapacitiveloadtoanenableddevicecancausea
momentaryovercurrentcondition;不管怎样,nofalsereportingonocxoccursduetothe10-msdeglitchcircuit.
thetps206xisdesignedtoeliminatefalseovercurrentreporting.theinternalovercurrentdeglitcheliminates
theneedforexternalcomponentstoremoveunwantedpulses.ocxisnotdeglitchedwhentheswitchisturned
offduetoanovertemperatureshutdown.
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