ꢀ
BL4054/BL4054B
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in SOT23-5/TSOT23-5
ꢀ
ꢀ
PROGꢀ pin.ꢀ Thisꢀ reducesꢀ theꢀ batteryꢀ drainꢀ
Applications Information
currentꢀ toꢀ lessꢀ thanꢀ 2
µAꢀ andꢀ theꢀ supplyꢀ
currentꢀ toꢀ lessꢀ thanꢀ 50
cycleꢀ canꢀ beꢀ initiatedꢀ byꢀ reconnectingꢀ theꢀ
µ
A.ꢀ Aꢀ newꢀ chargeꢀ
Stability Considerations
programꢀresistor.ꢀ ꢀ
ꢀ
Inꢀmanualꢀshutdown,ꢀtheꢀCHRGbꢀpinꢀisꢀinꢀaꢀ
weakꢀpullꢁdownꢀstateꢀasꢀlongꢀasꢀVCCꢀisꢀhighꢀ
enoughꢀ toꢀ exceedꢀ theꢀ UVLOꢀ conditions.ꢀ
Theꢀ CHRGbꢀ pinꢀ isꢀ inꢀ aꢀ highꢀ impedanceꢀ
stateꢀ ifꢀ theꢀ BL4054/BL4054Bꢀ isꢀ inꢀ underꢀ
voltageꢀ lockoutꢀ mode:ꢀ eitherꢀ VCC
100mVꢀofꢀtheꢀBATꢀpinꢀvoltageꢀorꢀinsufficientꢀ
Theꢀ constantꢁvoltageꢀ modeꢀ feedbackꢀ loopꢀ
isꢀ stableꢀ withoutꢀ anꢀ outputꢀ capacitorꢀ
providedꢀ aꢀ batteryꢀ isꢀ connectedꢀ toꢀ theꢀ
chargerꢀoutput.ꢀWithꢀnoꢀbatteryꢀpresent,ꢀanꢀ
outputꢀcapacitorꢀisꢀrecommendedꢀtoꢀreduceꢀ
rippleꢀvoltage.ꢀWhenꢀusingꢀhighꢀvalue,ꢀlowꢀ
ESRꢀceramicꢀcapacitors,ꢀitꢀisꢀrecommendedꢀ
toꢀ addꢀ aꢀ 1Ω resistorꢀ inꢀ seriesꢀ withꢀ theꢀ
capacitor.ꢀ Noꢀ seriesꢀ resistorꢀ isꢀ neededꢀ ifꢀ
tantalumꢀcapacitorsꢀareꢀused.ꢀ ꢀ
ꢀ isꢀ withinꢀ
voltageꢀisꢀappliedꢀtoꢀtheꢀVCCꢀpin.ꢀ
ꢀ
Over-Voltage Protect
ꢀ
Inꢀconstantꢁcurrentꢀmode,ꢀtheꢀPROGꢀpinꢀisꢀ
inꢀ theꢀ feedbackꢀ loop,ꢀ notꢀ theꢀ battery.ꢀ Theꢀ
constantꢁcurrentꢀ modeꢀ stabilityꢀ isꢀ affectedꢀ
byꢀtheꢀimpedanceꢀatꢀtheꢀPROGꢀpin.ꢀWithꢀnoꢀ
additionalꢀ capacitanceꢀ onꢀ theꢀ PROGꢀ pin,ꢀ
theꢀchargerꢀisꢀstableꢀwithꢀprogramꢀresistorꢀ
valuesꢀasꢀhighꢀasꢀ20k.ꢀHowever,ꢀadditionalꢀ
capacitanceꢀ onꢀ thisꢀ nodeꢀ reducesꢀ theꢀ
maximumꢀ allowedꢀ programꢀ resistorꢀ thusꢀ itꢀ
shouldꢀbeꢀavoided.ꢀ ꢀ
Theꢀ BL4054/BL4054Bꢀ hasꢀ anꢀ internalꢀ
OverꢁVoltageꢀProtectꢀcomparator,ꢀonceꢀtheꢀ
inputꢀvoltageꢀVCCꢀrisesꢀaboveꢀ7Vꢀ(VOVP),ꢀthisꢀ
comparatorꢀ willꢀ shutꢀ downꢀ theꢀ chip.ꢀ Thisꢀ
featureꢀ canꢀ preventꢀ theꢀ BL4054/BL4054Bꢀ
fromꢀtheꢀoverꢁvoltageꢀstressꢀdueꢀtoꢀtheꢀinputꢀ
transientꢀ atꢀ hotꢀ plugꢀ in.ꢀ Inꢀ thisꢀ state,ꢀ theꢀ
CHRGbꢀ pinꢀ willꢀ beꢀ highꢀ impedance.ꢀ Onceꢀ
theꢀVCCꢀfallsꢀbackꢀtoꢀsafeꢀrangeꢀ(VOVPꢀꢁꢀVOVP,ꢀ
HYS),ꢀnormalꢀoperationꢀcontinues.ꢀ
ꢀ
Automatic Recharge
ꢀ
Onceꢀ theꢀ chargeꢀ cycleꢀ isꢀ terminated,ꢀ theꢀ
BL4054/BL4054Bꢀcontinuouslyꢀmonitorsꢀtheꢀ
voltageꢀonꢀtheꢀBATꢀpinꢀusingꢀaꢀcomparatorꢀ
withꢀ aꢀ 2msꢀ filterꢀ timeꢀ (TRECHRG).ꢀ Aꢀ chargeꢀ
cycleꢀrestartsꢀwhenꢀtheꢀbatteryꢀvoltageꢀfallsꢀ
belowꢀ 4.05Vꢀ (whichꢀ correspondsꢀ toꢀ
approximatelyꢀ80%ꢀtoꢀ90%ꢀbatteryꢀcapacity).ꢀ
Thisꢀ ensuresꢀ thatꢀ theꢀ batteryꢀ isꢀ keptꢀ atꢀ orꢀ
nearꢀ aꢀ fullyꢀ chargedꢀ conditionꢀ andꢀ
eliminatesꢀ theꢀ needꢀ forꢀ periodicꢀ chargeꢀ
cycleꢀ initiations.ꢀ CHRGbꢀ outputꢀ entersꢀ aꢀ
strongꢀ pullꢁdownꢀ stateꢀ duringꢀ rechargeꢀ
cycles.ꢀ
ꢀ
Average,ꢀratherꢀthanꢀinstantaneous,ꢀchargeꢀ
currentꢀmayꢀbeꢀofꢀinterestꢀtoꢀtheꢀuser.ꢀForꢀ
example,ꢀ ifꢀ aꢀ switchingꢀ powerꢀ supplyꢀ
operatingꢀinꢀlowꢀcurrentꢀmodeꢀisꢀconnectedꢀ
inꢀ parallelꢀ withꢀ theꢀ battery,ꢀ theꢀ averageꢀ
currentꢀ beingꢀ pulledꢀ outꢀ ofꢀ theꢀ BATꢀ pinꢀ isꢀ
typicallyꢀ ofꢀ moreꢀ interestꢀ thanꢀ theꢀ
instantaneousꢀ currentꢀ pulses.ꢀ Inꢀ suchꢀ aꢀ
case,ꢀaꢀsimpleꢀRCꢀfilterꢀcanꢀbeꢀusedꢀonꢀtheꢀ
PROGꢀpinꢀtoꢀmeasureꢀtheꢀaverageꢀbatteryꢀ
currentꢀasꢀshownꢀinꢀFigureꢀ2.ꢀAꢀ10kꢀresistorꢀ
hasꢀ beenꢀ addedꢀ betweenꢀ theꢀ PROGꢀ pinꢀ
andꢀtheꢀfilterꢀcapacitorꢀtoꢀensureꢀstability.ꢀ ꢀ
ꢀ
Thermal Limiting
Anꢀinternalꢀthermalꢀfeedbackꢀloopꢀreducesꢀ
theꢀ programmedꢀ chargeꢀ currentꢀ ifꢀ theꢀ dieꢀ
ꢀ
PPMIC BU
BL4054/BL4054B Rev 1.4
5/2009
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