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FUNCTIONALDESCRIPTION
低-dropoutregulator(reg)
Initialization
OverloadDetection
短的-circuitdetection
overloadandshort-circuitdelay
overloadandshort-circuitresponse
bq29312A
SLUS629A–JANUARY2005–REVISEDAUGUST2005
theinputsforthisregulatorcanbederivedfromthebatterycellstack(bat)orthepackpositiveterminal
(包装).theoutputistypically3.3vwiththeminimumoutputcapacitanceforstableoperationis4.7µfandis
alsointernallycurrentlimited.duringnormaloperation,theregulatorlimitsoutputcurrenttotypically50ma.
thebq29312ainternalcontrolcircuitispoweredbytheregvoltage,whichitalsomonitors.whenthevoltageat
regfallsbelow2.3v,theinternalcircuitturnsoffthefetsanddisablesallcontrollablefunctions,includingthe
regandtoutoutputs.regdoesnotstartupunlessavoltageabovev
(startup)
issuppliedtothePACK
终端.aftertheregulatorhasstarted,basedonpackvoltage,itkeepsoperatingthroughthebatinput,甚至
ifthepackvoltageisremoved.ifthebatinputisbelowtheminimumoperatingrange,thenthebq29312adoes
notoperateifthesupplytothepackinputisremoved.afterstartup,whentheregvoltageisabove2.4v,这
bq29312aisinnormalmode.
theinitialstateofthechgoutputdependsonthepmsinput.ifpms=包装,thenchg=在,不管怎样,如果
pms=地,thenchg=止.
theoverloaddetectionisusedtodetectabnormalcurrentsinthedischargedirection.thisfeatureisusedto
protectthepassfets,cellsandanyotherinlinecomponentsfromexcessivecurrentconditions.thedetection
circuitalsoincorporatesablankingdelaybeforedrivingthecontrolforthepassfetstotheoffstate.这
overloadsensevoltageissetintheolvregister,anddelaytimeissetintheoltregister.theoverload
thresholdcanbeprogrammedfrom50mvto205mvin5-mvstepswiththedefaultbeing50mvandhysteresis
of10mv.
theshortcurrentcircuitdetectionisusedtodetectabnormalcurrentineitherthechargeordischargedirection.
thissafetyfeatureisusedtoprotectthepassfets,cells,andanyotherinlinecomponentsfromexcessive
currentconditions.thedetectioncircuitalsoincorporatesablankingdelaybeforedrivingthecontrolforthepass
fetstotheoffstate.theshort-circuitthresholdsanddelaytimearesetinthesccandscdregisters,
各自,wheresccisforchargingandscdisfordischarge.theshort-circuitthresholdcanbe
programmedfrom100mvto475mvin25-mvstepswiththedefaultbeing100mvandhysteresisof50mv.
theoverloaddelay(default=1ms)allowsthesystemtomomentarilyacceptahighcurrentconditionwithout
disconnectingthesupplytotheload.thedelaytimecanbeincreasedviatheoltregister,whichcanbe
programmedforarangeof1msto31mswithstepsof2ms.
theshort-circuitdelay(default=0µs)isprogrammableinthesccandscdregisters.thisregistercanbe
programmedfrom0µsto915µswithstepsof61µs.
whenanoverloadorshort-circuitfaultisdetected,thefetsareturnedoff.thestatus(b0
…
b2)寄存器
reportsthedetailsofshort-电路(承担),短的-电路(释放),andoverload.therespectivestatus
(b0
…
b2)bitsaresetto1andthexalertoutputistriggered.thisconditionislatcheduntilthecontrol(b0)
issetandthenreset.ifafetisturnedonviaresettingcontrol(b0)andtheerrorconditionisstillpresenton
thesystem,thenthedevicereenterstheprotectionresponsestate.
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