新筆記本電源芯片

a

FEATURES

Stand-AloneLi-IonBatteryChargers

HighFrequencySwit odeDualLi-IonBatteryChargers

ADP3801/ADP3802

FUNCTIONALBLOCKDIAGRAM

LDO+ GATEREFERENCEDRIVE

CURRENTLOOP

AMP+EOCCOMPARATOR

A/BSELECTMUX

SHUTDOWNUVLO

+

RESET

FINALBATTERYVOLTAGEPROGRAM

(4.2,8.4,12.6)

SD\UVLO

ADP3801/ADP3802

VOLTAGELOOPAMP

BATTERYVOLTAGEAJUST

10%

HighEnd-of-ChargeVoltageAccuracy0.4%@+25C

0.75%@–10Cto+70C

In ligentEnd-of-ChargeOutputSignalPinProgrbleCellNumberSelectOnChip3.3VLDORegulator

ProgrbleChargeCurrentwithHighSideSenseSoftstartChargeCurrent

UndervoltageLockoutDriveternalPMOS

10%AdjustableEnd-of-ChargeVoltage

ChargesNiCad,NiMH(withExternalmController)OscillatorFrequency:

ADP3801:200kHz

ADP3802:500kHz

VL

SDRESET

VCC

DRV

EOCCS+CS– A/B

BATABATBISET

PROG

APPLICATIONS

FastChargersUniversalChargersCellularPhonesPortableComputers

PortableInstrumentationDesktopChargers

alDigitalAssistants

GND

COMP

ADJ

GENERALDESCRIPTION

TheADP3801andADP3802arecompletebatterychargingICs.Thedevicescombineahighaccuracyfinalbatteryvoltagecontrolwithaconstantchargecurrentcontrolandanon-boardLowDrop-OutRegulator(LDO).Theaccuracyofthefinalbatteryvoltagecontrolisguaranteedto0.75%tosafelychargeLi-Ionbatteries.Aninternalmultiplexerallowsthealternatechargingoftwoseparatebatterystacks.ThefinalvoltageispinprogrbletooneofthreeLi-Ionoptions:4.2V(oneLi-Ioncell),8.4V(twoLi-Ioncells),or12.6V(threeLi-Ioncells).

Pairedwithanexternalmicrocontrollerforchargetermination,theADP3801/ADP3802worksasafastchargerforNiCad/NiMHbatteriesorasauniversalchargerforallthreebatterychemistries.Inaddition,apinisprovidedforchangingthefinalbatteryvoltagebyupto10%toadjustforvariationsinbatterychemistryfromdifferentLi-Ionmanufacturerswithoutlossofaccuracyinthefinalbatteryvoltage.

68mH 40mV

VIN

BATA

BATB

VCCDRV EOC CS+CS– A/B

3.3V

VL

BATA

BATB

SD

ADP3801/ADP3802

ISET

RESET

GND

COMP

PROG

ADJ

Figure1.4AmpDualBatteryCharger

REV.0

InformationfurnishedbyogDevicesisbelievedtobeaccurateandreliable.However,noresponsibilityisassumedbyogDevicesforitsuse,norforanyinfringementsofpatentsorotherrightsofthirdpartieswhiayresultfromitsuse.NolicenseisgrantedbyimplicationorotherwiseunderanypatentorpatentrightsofogDevices.

OneTechnologyWay,P.O.Box9106,Norwood,MA02062-9106,U.S.A.:781/329-4700 WorldWideWebSite:htt

Fax:781/326-8703 ?ogDevices,Inc.,1998

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ADP3801/ADP3802–SPECIFICATIONS(@–40CTA+85C,VCC=10.0V,unlessotherwisenoted)

Parameter

Conditions

Symbol

Min

Typ Max

Units

FINALBATTERYVOLTAGE

OneLi-IonCell

PROG=VT1,ADJ=VL,TA=+25C

VBAT

4.180

4.200 4.220

V

PROG=VT1,ADJ=VL,–10CTA+70C

VBAT

4.168

4.232

V

PROG=VT1,ADJ=VL,–40CTA+85C

VBAT

4.150

4.250

V

TwoLi-IonCells1

PROG=VT2,ADJ=VL,TA=+25C

VBAT

8.366

8.400 8.434

V

PROG=VT2,ADJ=VL,–10CTA+70C

VBAT

8.337

8.463

V

PROG=VT2,ADJ=VL,–40CTA+85C

VBAT

8.300

8.500

V

ThreeLi-IonCells1

PROG=VT3,ADJ=VL,TA=+25C

VBAT

12.550

12.600 12.650

V

PROG=VT3,ADJ=VL,–10CTA+70C

VBAT

12.505

12.695

V

PROG=VT3,ADJ=VL,–40CTA+85C

VBAT

12.450

12.750

V

BATTERYPROGRAMMING

INPUT(PROG)

OneLi-IonCell (4.2V)

VT1

0.00

0.20

V

TwoLi-IonCells (8.4V)

VT2

1.00

1.20

V

ThreeLi-IonCells (12.6V)

VT3

2.05

2.30

V

FailSafeVoltage (4.2V)

Defaultsto1Li-IonCell

3.10

3.30

V

PROGInputCurrent

IB

1.5 5

A

A/BSELECTMUX

SelectBatteryBATB

VIH

2.0

V

SelectBatteryBATA

VIL

0.8

V

A/BInputCurrent

A

IIN

0.02 1

BATAorBATBInput

ChannelSelected

RIN

185

265

k

BATAorBATBInputCurrent

ChannelNotSelected

IBA,IBB

0.2 1

A

BATAorBATBShutdownCurrent

PartinShutdown

A

IBA,IBB

0.2 1

BATTERYADJUSTINPUT2(ADJ)

%ofFinalBatteryVoltage

ADJ=1.0V,–10CTA+70C

89

90 91

%

%ofFinalBatteryVoltage

ADJ=2.3V,–10CTA+70C

109

110 111

%

ADJDisableVoltageThreshold

0%Change

2.475 2.6

V

ADJBiasCurrent

1.0VADJ2.3V

IB

10 100

nA

OVERVOLTAGECOMPARATOR

TripPointResponseTime

PercentAboveVBATDRVGoesHigh

tr

8

2

%

s

OSCILLATOR

200kHzOption

(ADP3801)

fOSC

150

200 250

kHz

500kHzOption

(ADP3802)

fOSC

375

500 625

kHz

0%DutyCycleThreshold

@COMPPin

1.0

V

100%DutyCycleThreshold

@COMPPin

2.0

V

GATEDRIVE

RiseTime

CL=1nF,VCC–4Vto90%

tr

35

ns

FallTime

CL=1nF,90%toVCC–4V

tf

75

ns

OutputHighSaturationVoltage

VCC–VDRV

VOH

275

mV

OutputLowVoltage

VCC=8V

VOL

1.0 2.0

V

VCC>8V

VOL

VCC–7VCC–6

V

CURRENSEAMPLIFIER

InputCommon-modeRange

VCS+andVCS–

VCSCM

0.0 VCC–2

V

InputDifferentialModeRange

VCS3

VCSDM

0.0 185

mV

InputOffsetVoltage4

0.0VVCSCMVCC–2V

VCSVOS

1

mV

InputBiasCurrent

0.0VVCSCMVCC–2V

VCSIB

0.3 1

A

InputOffsetCurrent

0.0VVCSCMVCC–2V

VCSIOS

0.01 0.15

A

OverCurrentTripPoint

VCS3

185

mV

ResponseTime

s

DRVGoesHigh

tr

2

ISETINPUT

ChargeCurrentProgramming

Function

0.0VVISET1.65V

VCS/V 3

ISET

0.1

V/V

ProgrammingFunctionAccuracy

VISET=1.65V,–10CTA+70C

–5

1.0 +5

%

VISET=0.10V,–10CTA+70C

–25

10 +25

%

ISETBiasCurrent

0.0VVISET1.65V

IB

15 100

nA

ADP3801/ADP3802

Parameter

Conditions

Symbol

Min

Typ Max

Units

EOCOUTPUT5

TripPointHysteresis

100ktoVL100ktoVL

VCS3VCS3

10

0.2

mVmV

SHUTDOWN(SD)

ON

SDH

2.0

V

OFF

SDInputCurrent

SDL

0.8

0.2 1

V

A

LOWDROPOUTREGULATOR

OutputVoltage6

0mAILOAD10mA,

4.1VVCC20V,–10CTA+70C

VL

3.267

3.3 3.333

V

0mAILOAD10mA,

4.1VVCC20V,–40CTA+85C

VL

3.250

3.350

V

DropoutVoltage(VCC–VL)

ILOAD=10mA

VDO

0.4 0.8

V

OutputCurrentDrive

IVL

10

20

mA

RESETOUTPUT

VLRisingThreshold

RESETHigh

2.5

2.7 2.9

V

VLFallingThreshold

RESETLow

2.4

2.55 2.8

V

OutputHighLogicLevel

1MtoGroundExternal

2.4

2.9

V

POWERSUPPLY

ONSupplyCurrentOFFSupplyCurrent

NoExternalLoadsNoExternalLoads

ISYONISYOFF

5.0 7.0

115 180

mA

A

UVLO6,7

VCCRisingThreshold

TurnOn

3.8

3.9 4.0

V

VCCFallingThreshold

TurnOff,IVL=1mA

3.4

V

NOTES

1VCC=VBAT+2V.

2SeeFigure5.

3VCS=(VCS+)–(VCS–).

4AccuracyguaranteedbyISETINPUT,ProgrammingFunctionAccuracyspecification.

5EOCOutputComparatormonitorschargecurrent,anditisenabledwhenVBAT95%ofthefinalbatteryvoltage.

6LsactiveduringSDandUVLO.

7Turn-offthresholddependsonLDOdropout.

AlllimitsattemperatureextremesareguaranteedviacorrelationusingstandardStatisticalQualityControl(SQC)methods.Specificationssubjecttochangewithoutnotice.

ADP3801/ADP3802

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ABSOLUTEUMRATINGS*

InputVoltage(VCCtoGND) Vto20V

DRV,VCS+,VCS–toGND 0.3VtoVCC

BATA,BATBtoGND Vto14.0V

A/B,ISET,PROG,ADJtoGND 0.3VtoVL

SD,RESET,COMP,EOCtoGND 0.3VtoVL

PowerDissipation InternallyLimited

JA 75C/W

AmbientTemperatureRange 40Cto+85C

StorageTemperatureRange 65Cto+150C

LeadTemperatureRange(Soldering10sec) +300C

ORDERINGGUIDE

Model

PackageOption

OscillatorFrequency

ADP3801AR

R-16A

200kHz

ADP3802AR

R-16A

500kHz

PINCONFIGURATION

NOTES

*Thisisastressratingonlyandfunctionaloperationofthedeviceattheseoranyotherconditionsabovethoseindicatedintheoperationsectionofthisspecificationisnotimplied.Exposuretoabsoluteumratingconditionsforextendedperiodsmayaffectdevicereliability.

JAisspecifiedforworstcaseconditionswithdevicesolderedonacircuitboard.

PINFUNCTIONDESCRIPTIONS

PinNumber

Mnemonic

Function

1

DRV

ExternalTransistorDrive

2

RESET

PoweronRESETOutput

3

VCC

SupplyVoltage

4

VL

LDOOutput

5

SD

ShutdownControlInput

6

CS–

NegativeCurren seInput

7

CS+

PositiveCurren seInput

8

ISET

ChargeCurrentProgramInput

9

COMP

ExternalCompensationNode

10

EOC

End-of-ChargeOutputSignal

11

ADJ

AdjustBatteryVoltage10%

12

PROG

ProgramFinalBatteryVoltageInput

13

BATB

Battery“B”VoltageSense

14

BATA

Battery“A”VoltageSense

15

A/B1

“A”or“B”BatterySelectInput

16

GND

Ground

NOTE

1“L”=Battery“A.”

DRVRESETVCC

8

VLSDCS–CS+ISET

GND

A/BBATABATBPROGADJEOC

COMP

CAUTION

WARNING!

ESDSENSITIVEDEVICE

ESD(electrostaticdischarge)sensitivedevice.Electrostaticchargesashighas4000Vreadilyaccumulateonthehumanbodyandtestequipmentandcandischargewithoutdetection.AlthoughtheADP3801/ADP3802featuresproprietaryESDprotectioncircuitry,permanentdamagemayoccurondevicessubjectedtohighenergyelectrostaticdischarges.Therefore,properESDprecau-tionsaremendedtoavoidperformancedegradationorlossoffunctionality.

TypicalPerformanceCharacteristics–ADP3801/ADP3802

VCC=10VTA=+25C

100

TOTALNUMBEROFPARTS

80

60

0.4

0.3

VBATACCURACY–%

0.2

0.1

0.3

VCC=10V

TA=+25CVBAT=4.2V

0.2

VBATACCURACY–%

0.1

40

20

0

–0.3 –0.1

0.1

0.3

0.5

0

–0.1

–0.2

–0.3

–0.4

0

–0.1

–0.2

–0.3

–0.5

–0.4

–0.2 0 0.2 0.4 0.6

–40

–20 0 20 40 60 80100

6 8 10 12 14 16

18 20

VBCURACY–%

Figure2.VBcuracyDistribution

TEMPERATURE–C

Figure3.VBcuracyvs.Temperature

SUPPLYVOLTAGE–Volts

Figure4.VBcuracyvs.SupplyVoltage

VCC=10VTA=+25C

VCC=10V

VCC=10V

15 10

VBATPERCENTCHANGE–%

10

9

5

0

–5

–10

8

THRESHOLD–%

THRESHOLD–mV

7

185

6

–15

0 0.51.01.52.0

2.5

3.03.5

5

–40–20 0 20 40 60

80100

180

–40–20 0 20 40

80100

VADJ–Volts

Figure5.VBATPercentChangevs.VADJ

TEMPERATURE–C

Figure6.OvervoltageComparatorThresholdvs.Temperature

TEMPERATURE–C

Figure7.OvercurrentComparatorThresholdvs.Temperature

TA=+25C

3.7

UVLOTRIPPOINT–Votts

3.6

0.3

VCC=10V

0.2

LDOACCURACY–%

0.1

0.2

TA=+25C

LDOACCURACY–%

0.1

3.5 0 0

3.4

–0.1

–0.2

–0.1

3.3

01234

567

8910

–0.3

–40

–20 0 20 40 60 80100

–0.2

4 6 8 1012

14161820

LDOLOADCURRENT–mA

Figure8.UVLOTripPoint-Offvs.LDOLoadCurrent

TEMPERATURE–C

Figure9.LDOAccuracyvs.Temperature

SUPPLYVOLTAGE–Volts

Figure10.LDOAccuracyvs.SupplyVoltage

ADP3801/ADP3802

ADP3801/ADP3802

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TA=+25C

0.4

0

215

DROPOUTVOLTAGE–Volts

0.3

0.2

–20

PSRR–dB

–40

–60

–80

205

FREQUENCY–kHz

195

185

0.1

01234

5678

910

–100

1.0E+011.0E+021.0E+031.0E+041.0E+051.0E+06

175

–40–20 0 20 40 60

VCC=10VTA=+25CCLDO=1mF

ADP3801

VCC=10V

80100

LOADCURRENT–mA

Figure11.LDODropoutVoltagevs.LoadCurrent

FREQUENCY–Hz

Figure12.LDOPSRRvs.Frequency

TEMPERATURE–C

Figure13.OscillatorFrequencyvs.Temperature

VCC=10VTA=+25C

12

10

8

6

4

2

0

VCC=10VCL=1nFTA=+25C

250ns/DIV

CH12.00V

M250nsCH1 9.40V

1

VCC=10V

100 0.4

SATURATIONVOLTAGE–Volts

80

DUTYCYCLE–%

DRV–Volts

0.3

60

40

0.2

20

0

0 0.5

1.0

1.5

2.02.53.0

3.5

0

–40

–20 0

20 40 60 80

100

VCOMP–Volts

Figure14.DutyCyclevs.COMPPinVoltage

TIME–ns

Figure15.DRVRiseandFallTimes

TEMPERATURE–C

Figure16.DRVHighSaturationVolt-agevs.Temperature

3.9

CLAMPVOLTAGE–Volts

3.8

3.7

3.6

5.5 15

TA=+85C

TA=+25C

TA=–40C

NOTSWITCHING

SD=ON

VCC=10VTA=+25C

50%DUTYCYCLE

ADP3802

ADP3801

POWERSUPPLYCURRENT–mA

POWERSUPPLYCURRENT–mA

13

5.0

11

4.5

9

4.0

7

VCC=10V

3.5

–40–20 0

20 40 60 80

100

3.5

4 8

12 16 20

5

0 0.5

1.0

1.5

2.0

2.5

TEMPERATURE–C

Figure17.DRVOutputLowVoltagewithVCC=10Vvs.Temperature

SUPPLYVOLTAGE–Volts

Figure18.PowerSupplyCurrentvs.SupplyVoltage@ThreeTemperatures

CAPACITIVELOAD–nF

Figure19.PowerSupplyCurrentvs.CapacitiveLoadonDRV

APPLICATIONSSECTION

PRODUCTDESCRIPTION

TheADP3801andADP3802arecomplei-Ionbatterycharg-ingICs.Combinedwithamicrocontroller,theyalsofunctionasvoltagelimited,CprogrbleconstantcurrentsourcechargersforNiCadandNiMHchemistries.UtilizinganexternalPMOSpasstransistor,thedevicesrealizeabucktypeconstantcurrent,constantvoltage(CCCV)chargercontrollerthatiscapableofcharginoseparatebatterypacksforsuchapplicationsasportablecomputerchargersandcellularphonechargers.TheFunctionalBlockDiagramshowstheICs’functionalblocks,whicharedetailedbelow:

A/BSELECTMUX—Two-channelmultiplexerforchargingtwobatterystacks.

FINALBATTERYVOLTAGEPROGRAM—Multiplexertoprogram4.2V,8.4V,or12.6Vfinalbatteryvoltage.

VOLTAGELOOPAMP—GM-typeamplifiertocontrolthefinalbatteryvoltage.Itincludesabuilt-inovervoltagecomparator.

EOCCOMPARATOR—End-of-chargedetectionoutputtosignalwhenthebatteryisfullycharged.

BATTERYVOLTAGEADJUST—Amplifiertoadjustthefinalbatteryvoltageupto10%.

CURRENTLOOPAMP—High-side-curren seamplifiertosenseandcontrolthechargecurrentataprogr blelevel.Itincludesanovercurrentcomparator.

—Pulsewidthmodulatorandoscillator(ADP3801-200kHz,ADP3802-500kHz).

GATEDRIVE—Gatedrivetocontrolanexternalpasstran-sistor.ItincludesaclamptolimitthedrivevoltagetoprotecttheexternalPMOS.

LDO+REFERENCE—3.3Vlowdropoutregulatortosup-plyanexternalmicrocrontrollerandforon-chipsupply.In-cludesaninternalprecisionreference(VREF=VL/2).

SHUTDOWN—Logicinputtoshutdownthecharger.TheLDOremainson.

UVLO—Undervoltagelockoutcircuittoshutdownthechargerforlowsupplyvoltages.

RESET—ActiveLOWoutputtoresetexternallogiconpower-up.

Duringcharging,theADP3801/ADP3802maintainsaconstant,progrblechargecurrent.Thehighsidecurrenseamplifierhaslowoffsetallowingtheuseofalowvoltagedropforcurrensing:165mVfortheumchargecurrent.Theinputcommon-moderangeextendsfromgroundtoVCC–2Vensuringcurrentcontroloverthefullchargingvolt-ageofthebattery,includingashortcircuitcondition.Ahighimpedancedcvoltageinput(ISET)isprovidedforprogram-mingthechargecurrentoverawiderange.Whenthebatteryvoltageapproachesitsfinallimit,thepartautomaticallytrans-ferstovoltagecontrolmode.Boththecurrentcontrolloopandthevoltagecontrolloopsharethesamecompensationpinmini-mizingthenumberofexternalcomponents.Aninternalcom-paratormonitorsthechargecurrenttodetect-of-charge(EOC).WhenthecurrentdecreasessuchthatVCS8mV,theEOCoutputpullslow.

A3.3VL susedtogeneratearegulatedsupplyforinternalcircuitry.Additionally,theLDOcandeliverupto10mAofcurrenttopowerexternalcircuitrysuchasamicrocontroller.AnUndervoltageLockout(UVLO)circuitisincludedtosafelyshutdownthechargingcircuitrywhentheinputvoltagedropsbelowitsminimumrating.Ashutdownpinisalsoprovidedtoturnoffthechargerwhen,forexample,thebatteryhasbeenfullycharged.TheLDOremainsactiveduringshutdownorUVLOandhasaquiescentcurrentof110A.

BatteryCharginerview

Figure20showsasimplifiedBucktypebatterychargerapplica-tioncircuitfortheADP3801/ADP3802.Whenadischargedbatteryisfirstcedinthecharger,thebatteryvoltageiswellbelowthefinalchargevoltage,sothecurrenseamplifiercontrolsthechargeloopinconstantcurrentmode.ThechargecurrentcreatesavoltagedropacrossthesenseresistorRCS.ThisvoltagedropisbufferedandamplifiedbyamplifierGM1.Am-plifierGM2comparestheoutputofGM1toanexternalcurrentcontrolvoltageprovidedattheISETpinandservosthechargerlooptomakethesevoltagesequal.Thus,thechargecurrentisprogrammedusingtheISETinputvoltage.

TheoutputofGM2isog“OR’ed”withtheoutputofGM3,thevoltageloopamplifier.Onlyoneortheotheramplifiercon-trolsthechargeloopatanygiventime.Asthebatteryvoltageapproachesitsfinalvoltage,GM3comesintobalance.Asthisoccurs,thechargecurrentdecreases,unbalancingGM2,andcontrolofthefeedbackloopnaturallytransferstoGM3.

TheADP3801/ADP3802cancontrolthechargingoftwoinde-pendentbatterystacksorasinglebatterystack.TheA/BSELECTMUXhasalogicinputtochoosebetweenthetwobatteries.SeeFigure31formoreinformationondualbatterycharging.Theoutputofthemultiplexerisappliedtoaprecisionthin-filmresistorstringtodividedownthebatteryvoltage.ThefinalbatteryvoltageischosenbyselectingtheproperresistordividertapwiththePROGmultiplexer.TheoutputofthismuxgoesdirectlytotheinputofGM3,comparingthedivideddownbatteryvoltagetotheinternalreference.Toguarantee0.75%accuracy,ahighprecisioninternalreferenceandhighaccuracythinfilmresistorsareused.Includingthesecomponentson-chipsavesthesignificantcostanddesigneffortofaddingthemexternally.

L

RCS

D2

VIN

CIN

D1COUT

RB

BA

Rf1

Rf2

VCC

DRV EOC

CS+

CS–

A/B

3.3V

BATA

MUX BATB

VL

GM1

(TOmC)

PROG

VREF

VT

RESET

VREF

UVLO

FINALVBATPROG

(TOmC)

VREF

GM2

SD

(FROMmC)

BIAS

Q

FFRS

ISET (FROMmC)

1mF

100kV

OSCILLATOR

GM3

3R

ADP3801/ADP3802

ADJ

(FROMmC)

R

1mF

100kV

2.475V

VREF

GND

COMP

POWER-ONRESET

LDO

GATEDRIVE

TA

Figure20.SimplifiedApplicationDiagram

SettingtheFinalBatteryVoltage

ThefinalbatteryvoltageisdeterminedbythevoltageontheBatteryProgramming(PROG)pin.ThispincontrolsthestateofthePROGmultiplexer,whichselectstheappropriatetapfromtheinternalbatteryvoltageresistordivider.Thespecifica-tiontabledetailsthePROGvoltagesforeachfinalbatteryvolt-age.AresistordividerfromtheLDOcanbeusedtosetthe

PROGvoltageasshowninFigure21.Toprovidefailsafeop-

VLPROG

VBAT

SETTING

R1(5%)

R2(5%)

4.2

VT1=0.0V

0*

8.4

VT2=1.1V

200kV

100kV

12.6

VT3=2.2V

100kV

200kV

R1R2

*CONNECTPROGTOGNDFORVBAT=4.2V

eration,aPROGvoltageequalto0.0Vor3.3Vresultsintheminimumfinalbatteryvoltageof4.2V.ThePROGinputishighimpedance,sothevoltagecanbesetwithahighimped-anceresistordividerfromVL.Alternatively,aoutputfromamicrocontrollercanbeusedwithanRCfiltertogeneratethedesiredthresholdvoltage.

Figure21.ResistorDividerSetstheFinalBatteryVoltage

AdjustingtheFinalBatteryVoltage

InadditiontothePROGinput,theADP3801/ADP3802pro-videsaninput(ADJ)forfineadjustmentofthefinalbatteryvoltage.Forexample,theADJamplifierallowsthenominal

4.2VpercellsettingforLi-Ionbatterycellstobeadjustedto

4.1Vrtainchemistries.AninternalamplifierbufferstheADJpinandadjuststheinternalreferencevoltageontheinputtoGM3.Figure5showsagraphofthepercentchangeinfinalbatteryvoltagevs.theADJvoltage.Thelinearportionbetween

0.6VREFand1.4VREFfollowstheformulabelow:

VADJVREF

ThesamecaremustbegiventothegroundconnectionfortheADP3801/ADP3802.Anyvoltagedifferencebetweenthebat-terygroundandtheGNDpinwillcauseanerrorinthechargevoltage.Thiserrorincludesthevoltagedropduetothegroundcurrentofthepart.Thus,theGNDpinshouldhaveathicktraceorgroundneconnectedascloseaspossibletothebattery’snegativeterminal.Anycurrentfromadditionalcir-cuitryshouldberoutedseparaytothesupplyreturnandnotshareatracewiththeGNDpin.

DualBatteryOperation

TheADP3801/ADP3802isdesignedtochargetwoseparate

VBAT%

4VREF

100

batterypacks.Thesebatteriescanbeofdifferentchemistriesandhaveadifferentnumberofcells.Atanygiventime,only

Thefactoroffourinthedenominatorisduetointernalscaling.WhenVADJisabove2.5V,aninternalcomparatorswitchesofftheADJamplifier,givinga0%changeinVBAT.WhenevertheADJfunctionisnotuseditshouldbeconnectedtoVL.

Thetotalrangeofadjustmentis10%.Forexample,the4.2Vfinalbatteryvoltagesettingcanbeadjustedfrom3.78Vto

4.62V.Ofcourse,caremustbetakennottoadjustthefinalbatteryvoltagetoanunsafecharginglevelforLi-Ionbatteries.Followthebatterymanufacturersspecificationsfortheappro-priatefinalbatteryvoltage.NeverchargeaLi-Ionbatteryabovethemanufacturersratedum!

VoltageLoopAccuracy

TheADP3801/ADP3802guaranteesthatthebatteryvoltagebewithin0.75%ofthesetpointoverthespecifiedtemperaturerangeandthespecifiedchargecurrentrange.Thisinclusivespecificationsavesthedesignerthetimeandexpenseofhavingtodesign-inadditionalhighaccuracycomponentssuchasareferenceandprecisionresistors.

Tomaintainthe0.75%specification,thelayoutanddesignoftheexternalcircuitrymustbeconsidered.TheinputimpedanceofBATAandBATBistypically265k,soanyadditionalim-pedanceontheseinputswillcauseanerror.Asaresult,donotaddexternalresistorstothebatteryinputs.Furthermore,iftheoutputvoltageisbeingusedforotherpurposes,suchastosup-plyadditionalcircuitry,thecurrenttothiscircuitryshouldberoutedseparayfromthesenselinestopreventvoltagedropsduetoimpedanceofthePC-boardtraces.Ingeneral,routethesenselinesasKelvinconnectionsasclosetothepositivetermi-nalsofthebatteryaspossible.

oneofthetwobatteriesisbeingcharged.Toselectwhichbat-teryisbeingmonitored,andthereforewhichbatteryisbeingcharged,theADP3801/ADP3802includesabatteryselectormux.Thistwo-channelmuxisdesignedtobe“break-before-make”toensurethatthetwobatteriesarenotshortedtogethermomentarilywhenswitchingfromonetotheother.TheA/Binputisastandardlogicinput,withalogiclowselectingBATAandalogichighselectingBATB.SeetheapplicationinFigure31formoreinformation.

OvervoltageComparator

GM3includesanovervoltagecomparator.ItsoutputbypassestheCOMPnodetoquicklyreducethedutycycleoftheto0%whenanovervoltageeventoccurs.AsecondoutputisconnectedtotheCOMPnodeand,withslowerresponse,re-ducesthevoltageontheCOMPcaptoprovideasoftstartre-covery.Thethresholdofthecomparatoristypically8%abovethefinalbatteryvoltage.Thiscomparatorprotectternalcircuitryfromanyconditionthatcausestheoutputvoltagetoquicklyincrease.Themostlikelyreasonisifthebatteryissuddenlyremovedwhileitisbeingchargedwithhighcurrent.Figure27showsthetransientresponsewhenthebatteryisremoved.Noticethattheoutputvoltageincreasestothecom-paratortrippoint,butitisquicklybroughtundercontrolandheldatthefinalbatteryvoltage.

CurrenseAmplifier

Adifferential,highsidecurrenseamplifier(GM1inFigure20)amplifiesthevoltagedropacrossacurrenseresistorRCS.Theinputcommon-moderangeofGM1extendsfromgroundtoVCC–2V.Sensingtogroundensurescurrentregu-lationeveninshortcircuitconditions.Tostaywithinthecom-mon-moderangeofGM1,VCCmustbeatleast2VgreaterthanthefinalbatteryvoltageoracircuitsuchasshowninFig-ure32mustbeused.RCfiltersareincludedtofilterouthighfrequencytransients,whichcouldsaturatetheinternalcircuitry.Thefilter’scutoffistypicallysetathalftheswitchingfrequencyoftheoscillator.

ThechargecurrentiscontrolledbythevoltageontheISETpinaccordingtothefollowingformula:

ICHARGEVISET

10RCS

Thefactorof10isduetheGM1’sgainof10V/V.Tosetachargecurrentof1.5AwithRCS=0.1,VISETmustbe1.5V.Figure22showsthelinearityofthechargecurrentcontrolasthevolt-ageisincreasedfrom0Vtotheprogrammedfinalbatteryvolt-age(12.6Vinthiscase).Itisimportanttostatethatthiscurveistakenwithanideal,zeroimpedanceload.AnactualLi-IonbatterywillexhibitamoregradualdropinchargecurrentduetotheinternalimpedanceofthebatteryasshowninFigure25.

3.5

3.0

ICHARGE–Amps

2.5

2.0

1.5

1.0

0.5

OvercurrentComparator

Similartothevoltageloop,thecurrentloopincludesacom-paratortoprotecttheexternalcircuitryfromanovercurrentevent.ThiscomparatortripswhenGM1’sdifferentialinputvoltageexceeds185mV.Liketheovervoltagecomparator,ithastwooutputstoquicklyreducethedutycycleto0%andtopro-videasoft-startrecovery.Theresponsetimeoftheinternalcomparatorisapproximay1s;however,thefilterontheinputofGM1mayslowdownthetotalresponsetimeoftheloop.

End-of-ChargeOutput

TheADP3801/ADP3802providesanactivelow,end-of-charge(EOC)logicoutputtosignalwhenthebatteryhascompletedcharging.ThetypicalLi-IonchargingcharacteristicinFigure25showsthatwhenthebatteryreachesitsfinalvoltagethecurrentdecreases.TodetermineEOC,aninternalcomparatorsenseswhenthecurrentfallsbelow6%offullscale,ensuringthatthebatteryhasbeenfullycharged.Thecomparatorhashysteresistopreventoscillationaroundthetrippoint.

Topreventfalsetriggering(suchasduringsoft-start),thecom-paratorisonlyenabledwhenthebatteryvoltageiswithin5%ofitsfinalvoltage.Asthebatteryischargingup,thecomparatorwillnotgolowevenifthecurrentfallsbelow6%aslongasthebatteryvoltageisbelow95%offullscale.Oncethebatteryhasrisenabove95%,thecomparatorisenabled.

Therearetwoimportantreasonsforthisfunctionality.First,whenthecircuitisinitiallypoweredon,thechargecurrentiszerobecauseofthesoftstart.Ifthecomparatorisnotgatedbythebatteryvoltage,thenEOCwouldgolowerroneously.Sec-ond,aprovisionmustbemadeforbatterydischarge.Assumethatabatteryhasbeenfullycharged.EOCgoeslow,andthechargerisgatedoff.Whenthebatteryvoltagefallsto95%,duetoself-dischargeforexample,EOCwillreturnhigh.Thenthechargercanstartupandtopoffthebattery,preventingthebatteryfrom“floating”at-of-chargevoltage.

TheEOCoutputhasmanypossibleusesasshowninFigure23.Onesimplefunctionistoterminatethechargingtopreventfloating(Figure23a).Itcanbeusedasalogicsignaltoamicrocontrollertoindicatethatthebatteryhasfinishedcharg-

0

2 3 4 5 6 7 8 9 10

VOUT–Volts

11 1213

ing.ThemicrocontrollercanthenswitchtothenextbatteryifappropriateorshutdowntheADP3801/ADP3802.Itcsobe

Figure22.CCCVCharacteristicwithIdealLoad

usedtoturnonanLEDtosignalchargecompletion(Figure23b).Usingaflip-flop,EOCcancontroltheswitchingfromB