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I
O (prechg)
V
(prechg)
K
(设置)
R
设置
(3)
BatteryChargeCurrent
I
O (输出)
V
(设置)
K
(设置)
R
设置
(4)
BatteryVoltageRegulation
PowerHandoff
bq24030,bq24031,bq24032,
bq24032a,bq24035,bq24038,bq24039
SLUS618C–AUGUST2004–REVISEDJUNE2005
thebqtiny-iiiactivatesasafetytimer,t
(prechg)
,duringtheconditioningphase.ifv
(lowv)
thresholdisnot
reachedwithinthetimerperiod,thebqtiny-iiiturnsoffthechargerandenunciatesfaultonthestat1and
stat2pins.thetimeoutisextendedifthechargecurrentisreducedbydppm.seethe
TimerFaultRecovery
sectionforadditionaldetails.
thebqtiny-iiiofferson-chipcurrentregulationwithprogrammablesetpoint.theresistorconnectedbetween
theiset1andvss,r
设置,
determinesthechargelevel.thechargelevelmaybereducedtogivethesystem
priorityoninputcurrent(seedppm).thev
(设置)
andK
(设置)
parametersarespecifiedinthespecificationstable.
whenpoweredfromausbport,theinputcurrentavailable(0.1a/0.5a)istypicallylessthantheprogrammed
(iset1)chargingcurrent,andtherefore,thedppmfeatureattemptstokeeptheoutputfrombeingpulleddown
byreducingthechargingcurrent.
forthebq24032/2a/8thechargelevel,duringacoperationonly(psel=高),canbechangedbyafactorof2
bysettingtheiset2pinhigh(fullcharge)orlow(halfcharge).thevoltageontheiset1pin,vset1,isdivided
by2wheninthehalfconstantcurrentchargemode.notethatwithpsellow,theiset2pincontrolsonlythe
0.1a/0.5ausbcurrentlevel.
Seethesectiontitled
电源-pathmanagement
foradditionaldetails.
thevoltageregulationfeedbackisthroughthebatpin.thisinputistieddirectlytothepositivesideofthe
batterypack.thebqtiny-iiimonitorsthebattery-packvoltagebetweenthebatandvsspins.whenthe
batteryvoltagerisestotheV
o(reg)
门槛,thevoltageregulationphasebeginsandthechargingcurrent
beginstotaperdown.
ifthebatteryisabsent,thebatpincyclesbetweenchargedone(v
o(reg)
)andcharging(batteryrefresh
门槛,~4.1v).看Figure11.
看Figure12forpowerupbybatteryinsertion.
asasafetybackup,thebqtiny-iiialsomonitorsthechargetimeinthechargemode.ifchargeisnotterminated
withinthistimeperiod,t
(chg)
,thebqtiny-iiiturnsoffthechargerandenunciatesfaultonthestat1and
stat2pins.seethedppmoperationundercase1forinformationonextendingthesafetytimerduringdppm
运作.seethe
TimerFaultRecovery
sectionforadditionaldetails.
thedesigngoaloftheicistokeepthesystempoweredatalltimes(outpin),firstbyeitherinput,acorusb,
prioritychosenbypsel(pselfeaturesethighinternallyonbq24039),andlastlybythebattery.theinput
powersourceisonlyconsideredpresentifitspower-goodstatusislow.thereisabreak-在之前-makeswitching
actionwhenswitchingbetweenactousborusbtoac,fort
sw-交流/usb
,wherethesystemcapacitanceshould
holdupthesystemvoltage.notethatthetransferofpoweroccurswhenthesourcespower-goodpingoeshigh
(打开-drainoutputhigh=powernotpresent),whichiswhentheinputsourcedropstothebattery'svoltage.ifthe
batteryisbelowauseablevoltage,thesystemmayreset.典型地,priortolosingtheinputpower,thebattery
wouldhavesomeuseablecapacity,andasystemresetwouldbeavoided.ifthebatterywasdeadormissing,
thesystemwouldlosepowerunlessthepselpinwasusedtotransferpowerpriortoshutdown.
ifthisisaconcern,thereisasimpleexternalsolution.externallytogglingthepsel(bq24030/1/2/2a/5/8)管脚
immediatelystartsthepower-transferprocess(doesnotwaitforinputtodroptothebattery'svoltage).thiscan
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