LTC4011 - High Efficiency Standalone Nickel Battery Charger · VIL Input Voltage Low CHEM (NiMH) l...
Transcript of LTC4011 - High Efficiency Standalone Nickel Battery Charger · VIL Input Voltage Low CHEM (NiMH) l...
LTC4011
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Typical applicaTion
FeaTures DescripTion
High Efficiency Standalone Nickel Battery Charger
applicaTions
n CompleteNiMH/NiCdChargerfor1to16Cellsn NoMicrocontrollerorFirmwareRequiredn 550kHzSynchronousPWMCurrentSourceControllern NoAudibleNoisewithCeramicCapacitorsn PowerPath™ControlSupportn ProgrammableChargeCurrent:5%Accuracyn WideInputVoltageRange:4.5Vto34Vn AutomaticTricklePrechargen –∆VFastChargeTerminationn Optional∆T/∆tFastChargeTerminationn AutomaticNiMHTop-OffChargen ProgrammableTimern AutomaticRechargen MultipleStatusOutputsn MicropowerShutdownn 20-LeadThermallyEnhancedTSSOPPackage
n IntegratedorStandaloneBatteryChargern PortableInstrumentsorConsumerProductsn Battery-PoweredDiagnosticsandControln Back-UpBatteryManagementL,LT,LTC,LTM,LinearTechnologyandtheLinearlogoareregisteredtrademarksofLinearTechnologyCorporation.PowerPathisatrademarkofLinearTechnologyCorporation.Allothertrademarksarethepropertyoftheirrespectiveowners.
TheLTC®4011providesacomplete,cost-effectivenickelbatteryfastchargesolutioninasmallpackageusingfewexternal components. A 550kHz PWM current sourcecontrollerandallnecessarychargeinitiation,monitoringandterminationcontrolcircuitryareincluded.
The LTC4011 automatically senses the presence of aDC adapter and battery insertion or removal. Heavilydischarged batteries are precharged with a trickle cur-rent.TheLTC4011cansimultaneouslyuseboth–∆Vand∆T/∆tfastchargeterminationtechniquesandcandetectvariousbattery faults. Ifnecessary, a top-off charge isautomaticallyappliedtoNiMHbatteriesafterfastcharg-ingiscompleted.TheICwillalsoresumechargingifthebatteryself-dischargesafterafullchargecycle.
AllLTC4011chargingoperationsarequalifiedbyactualchargetimeandmaximumaveragecellvoltage.Chargingmayalsobegatedbyminimumandmaximumtemperaturelimits.NiMHorNiCdfastchargeterminationparametersarepin-selectable.
IntegratedPowerPathcontrol supportensures that thesystemremainspoweredatalltimeswithoutallowingloadtransientstoadverselyaffectchargetermination.
2ANiMHBatteryCharger2ANiMHChargeCycleat1C
0.1µF
10µF
4.7µH
10µF
0.033µF 0.068µF
FAULTINFET
CHRG
FROMADAPTER
5V
TOCREADY
LTC4011
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pin conFiguraTionabsoluTe MaxiMuM raTings(Note 1)VCC (Input Supply) to GND......................... –0.3V to 36VDCIN to GND .............................................. –0.3V to 36VFAULT, CHRG, VCELL, VCDIV, SENSE, BAT, TOCor READY to GND ........................... –0.3V to VCC + 0.3VSENSE to BAT ........................................................±0.3VCHEM, VTEMP or TIMER to GND ................ –0.3V to 3.5VPGND to GND .........................................................±0.3VOperating Ambient Temperature Range(Note 2) ........................................................ 0°C to 85°COperating Junction Temperature (Note 3) ............. 125°CStorage Temperature Range ...................–65°C to 150°CLead Temperature (Soldering, 10 sec) .................. 300°C
(Note 4) The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V, BAT = 4.8V, GND = PGND = 0V, unless otherwise noted.elecTrical characTerisTicsSYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VCC Supply
VCC Input Voltage Range l 4.5 34 V
ISHDN Shutdown Quiescent Current (Note 5) VCC = BAT = 4.8V 5 10 µA
IQ Quiescent Current Waiting to Charge (Pause) l 3 5 mA
ICC Operating Current Fast Charge State, No Gate Load l 5 9 mA
VUVLO Undervoltage Threshold Voltage VCC Increasing l 3.85 4.2 4.45 V
VUV(HYST) Undervoltage Hysteresis Voltage 170 mV
VSHDNI Shutdown Threshold Voltage DCIN – VCC, DCIN Increasing l 5 30 60 mV
VSHDND Shutdown Threshold Voltage DCIN – VCC, DCIN Decreasing l –60 –25 –5 mV
VCE Charge Enable Threshold Voltage VCC – BAT, VCC Increasing l 400 510 600 mV
INTVDD Regulator
VDD Output Voltage No Load l 4.5 5 5.5 V
IDD Short-Circuit Current (Note 6) INTVDD = 0V l –100 –50 –10 mA
INTVDD(MIN) Output Voltage VCC = 4.5V, IDD = –10mA l 3.85 V
FE PACKAGE20-LEAD PLASTIC TSSOP
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TOP VIEW
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DCIN
FAULT
CHRG
CHEM
GND
VRT
VTEMP
VCELL
VCDIV
TIMER
INFET
READY
VCC
TGATE
PGND
BGATE
INTVDD
TOC
BAT
SENSE
21
TJMAX=125°C,θJA=38°C/W
EXPOSEDPAD(PIN21)ISGND,MUSTBESOLDEREDTOPCBTOOBTAINSPECIFIEDTHERMALRESISTANCE
orDer inForMaTionLEADFREEFINISH TAPEANDREEL PARTMARKING PACKAGEDESCRIPTION TEMPERATURERANGE
LTC4011CFE#PBF LTC4011CFE#TRPBF LTC4011CFE 20-LeadPlasticTSSOP 0°Cto85°C
LEADBASEDFINISH TAPEANDREEL PARTMARKING PACKAGEDESCRIPTION TEMPERATURERANGE
LTC4011CFE LTC4011CFE#TR LTC4011CFE 20-LeadPlasticTSSOP 0°Cto85°C
ConsultLTCMarketingforpartsspecifiedwithwideroperatingtemperatureranges.Formoreinformationonleadfreepartmarking,goto:http://www.linear.com/leadfree/Formoreinformationontapeandreelspecifications,goto:http://www.linear.com/tapeandreel/
LTC4011
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elecTrical characTerisTicsSYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Thermistor Termination
VRT Output Voltage RL = 10k
l
3.0753
3.3 3.5253.6
VV
IRT Short-Circuit Current VRT = 0V l –9 –1 mA
PWM Current Source
VFS BAT – SENSE Full-Scale Regulation Voltage (Fast Charge)
0.3V < BAT < VCC – 0.3V (Note 5) BAT = 4.8V
l
9595
100100
105105
mVmV
VPC BAT – SENSE Precharge Regulation Voltage 0.3V < BAT < VCC – 0.3V (Note 5) BAT = 4.8V
l
1616
2020
2424
mVmV
VTC BAT – SENSE Top-Off Charge Regulation Voltage
0.3V < BAT < VCC – 0.3V (Note 5) BAT = 4.8V
l
6.56.5
1010
13.513.5
mVmV
∆VLI BAT – SENSE Line Regulation 5.5V < VCC < 25V, Fast Charge ±0.3 mV
IBAT BAT Input Bias Current 0.3V < BAT < VCC – 0.1V –2 2 mA
ISENSE SENSE Input Bias Current SENSE = BAT 50 150 µA
IOFF Input Bias Current SENSE or BAT, VCELL = 0V l –1 0 1 µA
fTYP Typical Switching Frequency l 460 550 640 kHz
fMIN Minimum Switching Frequency l 20 30 kHz
DCMAX Maximum Duty Cycle 98 99 %
VOL(TG) TGATE Output Voltage Low (VCC – TGATE, Note 7)
VCC > 9V, No Load VCC < 7V, No Load
l
l
5VCC–0.5
5.6VCC
8.75 VV
VOH(TG) TGATE Output Voltage High VCC – TGATE, No Load l 0 50 mV
tR(TG) TGATE Rise Time CLOAD = 3nF, 10% to 90% 35 100 ns
tF(TG) TGATE Fall Time CLOAD = 3nF, 10% to 90% 45 100 ns
VOL(BG) BGATE Output Voltage Low No Load l 0 50 mV
VOH(BG) BGATE Output Voltage High No Load l INTVDD–0.075 INTVDD V
tR(BG) BGATE Rise Time CLOAD = 1.6nF, 10% to 90% 35 80 ns
tF(BG) BGATE Fall Time CLOAD = 1.6nF, 10% to 90% 15 80 ns
ADC Inputs
ILEAK Analog Channel Leakage 0V < VCELL < 2V, 550mV < VTEMP < 2V ±100 nA
Charger Thresholds
VBP Battery Present Threshold Voltage l 320 350 370 mV
VBOV Battery Overvoltage l 1.815 1.95 2.085 V
VMFC Minimum Fast Charge Voltage l 850 900 950 mV
VFCBF Fast Charge Battery Fault Voltage l 1.17 1.22 1.27 V
∆VTERM –∆V Termination CHEM OPEN (NiCd) CHEM = 0V (NiMH)
l
l
166
2010
2514
mVmV
VAR Automatic Recharge Voltage VCELL Decreasing l 1.260 1.325 1.390 V
∆TTERM ∆TTermination(Note8) CHEM = 3.3V (NiCd) CHEM = 0V (NiMH)
l
l
1.30.5
21
2.71.5
°C/min°C/min
TMIN Minimum Charging Temperature (Note 8) VTEMP Increasing l 0 5 9 °C
TMAXI Maximum Charge Initiation Temperature (Note 8)
VTEMP Decreasing, Not Charging l 41.5 45 47 °C
The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V, BAT = 4.8V, GND = PGND = 0V, unless otherwise noted.
LTC4011
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SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
TMAXC Maximum Fast Charge Temperature (Note 8)
VTEMP Decreasing, Fast Charge l 57 60 63 °C
VTEMP(D) VTEMP Disable Threshold Voltage l 2.8 3.3 V
VTEMP(P) Pause Threshold Voltage l 130 280 mV
Charger Timing
∆tTIMER Internal Time Base Error l –10 10 %
∆tMAX Programmable Timer Error RTIMER = 49.9k l –20 20 %
PowerPath Control
VFR INFET Forward Regulation Voltage DCIN – VCC l 15 55 100 mV
VOL(INFET) Output Voltage Low VCC – INFET, No Load l 3.75 5.2 7 V
VOH(INFET) Output Voltage High VCC – INFET, No Load l 0 50 mV
tOFF(INFET) INFET OFF Delay Time CLOAD = 10nF, INFET to 50% 3 15 µs
Status and Chemistry Select
VOL Output Voltage Low (ILOAD = 10mA) VCDIV All Other Status Outputs
l
l
435300
700600
mVmV
ILKG Output Leakage Current All Status Outputs Inactive, VOUT = VCC l –10 10 µA
IIH(VCDIV) Input Current High VCDIV = VBAT (Shutdown) l –1 1 µA
VIL Input Voltage Low CHEM (NiMH) l 900 mV
VIH Input Voltage High CHEM (NiCd) l 2.85 V
IIL Input Current Low CHEM = GND l –20 –5 µA
IIH Input Current High CHEM = 3.3V l –20 20 µA
elecTrical characTerisTics The l indicates specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 12V, BAT = 4.8V, GND = PGND = 0V, unless otherwise noted.
Note1:StressesbeyondthoselistedunderAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.ExposuretoanyAbsoluteMaximumRatingconditionforextendedperiodsmayaffectdevicereliabilityandlifetime.Note2:TheLTC4011Cisguaranteedtomeetperformancespecificationsfrom0°Cto70°C.Specificationsoverthe0°Cto85°Coperatingtemperaturerangeareassuredbydesign,characterizationandcorrelationwithstatisticalprocesscontrols.Note3:OperatingjunctiontemperatureTJ(in°C)iscalculatedfromtheambienttemperatureTAandthetotalcontinuouspackagepowerdissipationPD(inwatts)bytheformula: TJ=TA+θJA•PDRefertotheApplicationsInformationsectionfordetails.ThisICincludesovertemperatureprotectionthatisintendedtoprotectthedeviceduringmomentaryoverloadconditions.Junctiontemperaturewillexceed125°C
whenovertemperatureprotectionisactive.Continuousoperationabovethespecifiedmaximumoperatingjunctiontemperaturemayresultindevicedegradationorfailure.Note4:Allcurrentintodevicepinsispositive.Allcurrentoutofdevicepinsisnegative.AllvoltagesarereferencedtoGND,unlessotherwisespecified.Note5:Theselimitsareguaranteedbycorrelationtowaferlevelmeasurements.Note6:Outputcurrentmaybelimitedbyinternalpowerdissipation.RefertotheApplicationsInformationsectionfordetails.Note7:EitherTGATEVOHmayapplyfor7.5V<VCC<9V.Note8:TheselimitsapplyspecificallytothethermistornetworkshowninFigure5intheApplicationsInformationsectionwiththevaluesspecifiedfora10kNTC(βof3750).LimitsarethenguaranteedbyspecificVTEMPvoltagemeasurementsduringtest.
LTC4011
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Typical perForMance characTerisTicsNiCdChargeCycleat1C NiCdChargeCycleat2C
NiMHChargeCycleat0.5CBatteryPresentThresholdVoltage(perCell)
MinimumFastChargeThresholdVoltage(perCell)
AutomaticRechargeThresholdVoltage(perCell)
BatteryOvervoltageThresholdVoltage(perCell) –∆VTerminationVoltage(perCell)
LTC4011
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Typical perForMance characTerisTicsProgrammableTimerAccuracy ChargeCurrentAccuracy
ChargerEfficiencyatIOUT=2A ChargerSoft-StartFastChargeCurrentLineRegulation
FastChargeCurrentOutputRegulation
PWMSwitchingFrequency
INFETForwardRegulationVoltage INFETOFFDelayTime
LTC4011
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Typical perForMance characTerisTicsPowerPathSwitching
100µs/DIV
CURR
ENT
(µA)
CURR
ENT
(µA)
ShutdownQuiescentCurrent PWMInputBiasCurrent(OFF)
UndervoltageLockoutThresholdVoltage
ShutdownThresholdVoltage(DCIN–VCC)
ChargeEnableThresholdVoltage(VCC–BAT)
ThermistorDisableThresholdVoltage PauseThresholdVoltage
LTC4011
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pin FuncTionsDCIN(Pin1):DCPowerSenseInput.TheLTC4011sensesvoltage on this pin to determine when an external DCpowersource ispresent.This inputshouldbe isolatedfromVCCbyablockingdiodeorPowerPathFET.RefertotheApplicationsInformationsectionforcompletedetails.OperatingvoltagerangeisGNDto34V.
FAULT (Pin 2): Active-Low Fault Indicator Output. TheLTC4011indicatesvariousbatteryandinternalfaultcondi-tionsbyconnectingthispintoGND.RefertotheOperationandApplicationsInformationsectionsforfurtherdetails.ThisoutputiscapableofdrivinganLEDandshouldbeleftfloatingifnotused.FAULTisanopen-drainoutputtoGNDwithanoperatingvoltagerangeofGNDtoVCC.
CHRG(Pin3):Active-LowChargeIndicatorOutput.TheLTC4011indicatesitisprovidingchargetothebatterybyconnectingthispintoGND.RefertotheOperationandApplicationsInformationsectionsforfurtherdetails.Thisoutput iscapableofdrivinganLEDandshouldbe leftfloatingifnotused.CHRGisanopen-drainoutputtoGNDwithanoperatingvoltagerangeofGNDtoVCC.
CHEM(Pin4):BatteryChemistrySelection Input.ThispinshouldbewiredtoGNDtoselectNiMHfastchargeterminationparameters.Ifavoltagegreaterthan2.85Visappliedtothispin,oritisleftfloating,NiCdparametersareused.RefertotheApplicationsInformationsectionforfurtherdetails.OperatingvoltagerangeisGNDto3.3V.
GND (Pin5):Ground.Thispinprovidesa single-pointgroundfor internalreferencesandothercriticalanalogcircuits.
VRT(Pin6):ThermistorNetworkTerminationOutput.TheLTC4011provides3.3VonthispintodriveanexternalthermistornetworkconnectedbetweenVRT,VTEMPandGND.Additionalpowershouldnotbedrawnfromthispinbythehostapplication.
VTEMP(Pin7):BatteryTemperatureInput.AnexternalthermistornetworkmaybeconnectedtoVTEMPtoprovidetemperature-based chargequalification and additionalfastchargeterminationcontrol.ChargingmayalsobepausedbyconnectingtheVTEMPpintoGND.RefertotheOperationandApplicationsInformationsectionsforcompletedetailsonexternal thermistornetworks andchargecontrol.IfthispinisnotuseditshouldbewiredtoVRT.OperatingvoltagerangeisGNDto3.3V.
VCELL(Pin8):AverageSingle-CellVoltageInput.Anexter-nalvoltagedividerbetweenBATandVCDIVisattachedtothispintomonitortheaveragesingle-cellvoltageofthebatterypack.TheLTC4011usesthisinformationtoprotectagainstcatastrophicbatteryovervoltageandtocontrolthechargingstate.RefertotheApplicationsInformationsectionforfurtherdetailsontheexternaldividernetwork.OperatingvoltagerangeisGNDtoBAT.
INTVDDVoltage INTVDDShort-CircuitCurrent
Typical perForMance characTerisTics
LTC4011
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pin FuncTionsVCDIV(Pin9):AverageCellVoltageResistorDividerTermi-nation.TheLTC4011connectsthispintoGNDprovidedthechargerisnotinshutdown.VCDIVisanopen-drainoutputtoGNDwithanoperatingvoltagerangeofGNDtoBAT.
TIMER(Pin10):ChargeTimerInput.AresistorconnectedbetweenTIMERandGNDprogramschargecycletiminglimits.RefertotheApplicationsInformationsectionforcompletedetails.OperatingvoltagerangeisGNDto1V.
SENSE(Pin11):ChargeCurrentSenseInput.AnexternalresistorbetweenthisinputandBATisusedtoprogramcharge current. Refer to the Applications Informationsection for complete details on programming chargecurrent.Operatingvoltagerangesfrom(BAT–50mV)to(BAT+200mV).
BAT(Pin12):BatteryPackConnection.TheLTC4011usesthevoltageonthispintocontrolcurrentsourcedfromVCCtothebatteryduringcharging.AllowableoperatingvoltagerangeisGNDtoVCC.
TOC(Pin13):Active-LowTop-OffChargeIndicatorOut-put.TheLTC4011indicatesthetop-offchargestateforNiMHbatteriesbyconnectingthispintoGND.RefertotheOperationandApplicationsInformationsectionsforfurtherdetails.ThisoutputiscapableofdrivinganLEDandshouldbeleftfloatingifnotused.TOCisanopen-drainoutputtoGNDwithanoperatingvoltagerangeofGNDtoVCC.
INTVDD(Pin14):Internal5VRegulatorOutput.Thispinprovidesameansofbypassingtheinternal5VregulatorusedtopowertheBGATEoutputdriver.Typically,powershould not be drawn from this pin by the applicationcircuit.Refer totheApplicationInformationsectionforadditionaldetails.
BGATE(Pin15):ExternalSynchronousN-channelMOSFETGateControlOutput.ThisoutputprovidesgatedrivetoanoptionalexternalNMOSpowertransistorswitchusedforsynchronousrectificationtoincreaseefficiencyinthestep-downDC/DCconverter.OperatingvoltageisGNDtoINTVDD.BGATEshouldbeleftfloatingifnotused.
PGND(Pin16):PowerGround.ThispinprovidesareturnforswitchingcurrentsgeneratedbyinternalLTC4011cir-cuits.Externally,PGNDandGNDshouldbewiredtogetherusing a very low impedance connection. Refer to PCBLayout Considerations in the Applications Informationsectionforadditionalgroundingdetails.
TGATE(Pin17):ExternalP-channelMOSFETGateControlOutput.ThisoutputprovidesgatedrivetoanexternalPMOSpowertransistorswitchusedintheDC/DCconverter.Op-eratingvoltagerangevariesasafunctionofVCC.RefertotheElectricalCharacteristicstableforspecificvoltages.
VCC(Pin18):PowerInput.ExternalPowerPathcontrolcircuitsnormallyconnecteithertheDCinputpowersup-plyor thebattery to thispin.Refer to theApplicationsInformationsectionforfurtherdetails.SuggestedappliedvoltagerangeisGNDto34V.
READY (Pin 19): Active-Low Ready-to-Charge Output.TheLTC4011connectsthispintoGNDifproperoperatingvoltagesforchargingarepresent.RefertotheOperationsectionforcompletedetailsonchargequalification.Thisoutput iscapableofdrivinganLEDandshouldbe leftfloating ifnotused.READY isanopen-drainoutput toGNDwithanoperatingvoltagerangeofGNDtoVCC.
INFET(Pin20):PowerPathControlOutput.Forverylowdropoutapplications, thisoutputmaybeused todrivethe gate of an input PMOS pass transistor connectedbetweentheDCinput(DCIN)andtherawsystemsupplyrail(VCC).INFETisinternallyclampedabout6VbelowVCC.MaximumoperatingvoltageisVCC.INFETshouldbeleftfloatingifnotused.
Exposed Pad (Pin 21): This pin provides enhancedthermalpropertiesfortheTSSOP.ItmustbesolderedtothePCBcoppergroundtoobtainoptimumthermalperformance.
LTC4011
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block DiagraM
7
8
13
14
CHARGERSTATE
CONTROLLOGIC
THERMISTORINTERFACE
A/DCONVERTER
BATTERYDETECTOR
VOLTAGEREGULATOR
UVLO ANDSHUTDOWN
PWM
FET DIODE
CHARGETIMER
VOLTAGEREFERENCE
INTERNALVOLTAGE
REGULATOR
VTEMP
6VRT
4CHEM
3CHRG
2FAULT
1
12
11
15
16
17
DCIN
5 GND
VCELL
10TIMER
9VCDIV
TOC
INTVDD
4011 BD
SENSE
BAT
PGND
19READY
INFET
VCC
BGATE
TGATE
20
18
LTC4011
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operaTion
Figure1.LTC4011StateDiagram
LTC4011
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operaTionShutdownState
TheLTC4011remainsinmicropowershutdownuntilDCIN(Pin1)isdrivenaboveVCC(Pin18).InshutdownallstatusandPWMoutputsandinternallygeneratedterminationsorsupplyvoltagesareinactive.CurrentconsumptionfromVCCandBATisreducedtoaverylowlevel.
ChargeQualificationState
Once DCIN is greater than VCC, the LTC4011 exitsmicropowershutdown,enablesitsowninternalsupplies,providesVRTvoltagefortemperaturesensing,andswitchesVCDIVtoGNDtoallowmeasurementoftheaveragesingle-cellvoltage.TheICalsoverifiesthatVCCisatorabove4.2V,VCCis510mVaboveBATandVCELLisbetween350mVand1.95V.IfVCELLisbelow350mV,nochargingwilloccur,andifVCELLisabove1.95V,thefaultstateisentered,whichisdescribedinmoredetailbelow.Onceadequatevoltageconditionsexistforcharging,READYisasserted.
IfthevoltagebetweenVTEMPandGNDisbelow200mV,theLTC4011ispaused.IfVTEMPisabove200mVbutbelow2.85V,theLTC4011verifiesthatthesensedtemperatureisbetween5°Cand45°C.Ifthesetemperaturelimitsarenotmetorifitsowndietemperatureistoohigh,theLTC4011willindicateafaultandnotallowchargingtobegin.IfVTEMPisgreaterthan2.85V,batterytemperaturerelatedchargequalification,monitoringandterminationaredisabled.
Oncechargingisfullyqualified,prechargebegins(unlesstheLTC4011 ispaused). In thatcase, theVTEMPpin ismonitoredforfurthercontrol.ThechargestatusindicatorsandPWMoutputsremaininactiveuntilchargingbegins.
ChargeMonitoring
TheLTC4011continuestomonitorimportantvoltageandtemperatureparametersduringallchargingstates.IftheDCinputisremoved,chargingstopsandtheshutdownstateisentered.IfVCCdropsbelow4.25VorVCELLdropsbelow350mV,chargingstopsandtheLTC4011returnstothechargequalificationstate.IfVCELLexceeds1.95V,chargingstopsandtheICentersthefaultstate.Ifanexternalthermistorindicatessensedtemperatureisbeyondarangeof5°Cto60°C,ortheinternaldietemperatureexceedsaninternalthermallimit,chargingissuspended,thechargetimerispausedandtheLTC4011indicatesafaultcondition.
Normalchargingresumesfromthepreviousstatewhenthesensedtemperaturereturnstoasatisfactoryrange.Inaddition,otherbatteryfaultsaredetectedduringspecificchargingstatesasdescribedbelow.
PrechargeState
IftheinitialvoltageonVCELLisbelow900mV,theLTC4011enterstheprechargestateandenablesthePWMcurrentsourcetotricklechargeusingone-fifththeprogrammedchargecurrent.TheCHRGstatusoutputisactiveduringprecharge. The precharge state duration is limited totMAX/12minutes,wheretMAXisthemaximumfastchargeperiodprogrammedwiththeTIMERpin.IfsufficientVCELLvoltagecannotbedevelopedinthislengthoftime,thefaultstateisentered,otherwisefastchargebegins.
FastChargeState
Ifadequateaveragesingle-cellvoltageexists,theLTC4011entersthefastchargestateandbeginschargingattheprogrammedcurrent set by the external current senseresistor connected between the SENSE and BAT pins.TheCHRGstatusoutputisactiveduringfastcharge.IfVCELLisinitiallyabove1.325V,voltage-basedterminationprocessingbeginsimmediately.Otherwise–∆Vterminationisdisabledforastabilizationperiodof tMAX/12. In thatcase,theLTC4011makesanotherfaultcheckattMAX/12,requiringtheaveragecellvoltagetobeabove1.22V.Thisensures the battery pack is accepting a fast charge. IfVCELLisnotabovethisvoltagethreshold,thefaultstateisentered.FastchargestatedurationislimitedtotMAXandthefaultstateisenteredifthislimitisexceeded.
ChargeTermination
FastchargeterminationparametersaredependentuponthebatterychemistryselectedwiththeCHEMpin.Voltage-basedtermination(–∆V)isalwaysactiveaftertheinitialvoltagestabilizationperiod.Ifanexternalthermistornetworkispresent,chemistry-specificlimitsfor∆T/∆t(rateoftem-peraturerise)arealsousedintheterminationalgorithm.Temperature-basedtermination,ifenabled,becomesactiveassoonas the fast chargestate isentered.SuccessfulchargeterminationrequiresachargeratebetweenC/2and2C.Lowerratesmaynotproducethebatteryvoltageandtemperatureprofilerequiredforchargetermination.
(RefertoFigure1)
LTC4011
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operaTionTop-OffChargeState
IfNiMHfastchargeterminationoccursbecausethe∆T/∆tlimitisexceededafteraninitialperiodoftMAX/12hasexpired,theLTC4011entersthetop-offchargestate.Top-offchargeisimplementedbysourcingone-tenththeprogrammedchargecurrentfortMAX/3minutestoensurethat100%chargehasbeendeliveredtothebattery.TheCHRGandTOCstatusoutputsareactiveduringthetop-offstate.IfNiCdcellshavebeenselectedwiththeCHEMpin,theLTC4011neverentersthetop-offstate.
AutomaticRechargeState
Oncechargingiscomplete,theautomaticrechargestateisentered toaddress theself-dischargecharacteristicsofnickelchemistrycells.Thechargestatusoutputsareinactive during automatic recharge, but VCDIV remainsswitchedtoGNDtomonitortheaveragecellvoltage.IftheVCELLvoltagedropsbelow1.325Vwithoutfallingbelow350mV,thechargetimerisresetandanewfastchargecycleisinitiated.
The internal terminationalgorithmsoftheLTC4011areadjustedwhenafastchargecycleisinitiatedfromauto-maticrecharge,becausethebatteryshouldbealmostfullycharged.Voltage-basedterminationisenabledimmediatelyandtheNiMH∆T/∆tlimitisfixedatabatterytemperatureriseof1°C/minute.
FaultState
Asdiscussedpreviously,theLTC4011entersthefaultstatebasedondetectionofinvalidbatteryvoltagesduringvari-ouschargingphases.TheICalsomonitorstheregulationofthePWMcontrolloopandwillenterthefaultstateifthisisnotwithinacceptablelimits.Onceinthefaultstate,thebatterymustberemovedorDCinputpowermustbecycled inorder to initiate further charging. In the faultstate, theFAULT output is active, theREADY output isinactive,chargingstopsandthechargeindicatoroutputsareinactive.TheVCDIVoutputremainsconnectedtoGNDtoallowdetectionofbatteryremoval.
NotethattheLTC4011alsousestheFAULToutputtoindi-catethatchargingissuspendedduetoinvalidbatteryorinternaldietemperatures.However,theICdoesnotenterthefaultstateinthesecasesandnormaloperationwill
resumewhenalltemperaturesreturntoacceptablelevels.RefertotheStatusOutputssectionformoredetail.
InsertionandRemovalofBatteries
TheLTC4011automaticallysensestheinsertionorremovalofabatterybymonitoringtheVCELLpinvoltage.Shouldthisvoltagefallbelow350mV,theICconsidersthebat-terytobeabsent.RemovingandtheninsertingabatterycausestheLTC4011toinitiateacompletelynewchargecyclebeginningwithchargequalification.
ExternalPauseControl
Afterchargingisinitiated,theVTEMPpinmaybeusedtopauseoperationatanytime.WhenthevoltagebetweenVTEMP and GND drops below 200mV, the charge timerpauses,fastchargeterminationalgorithmsareinhibitedandthePWMoutputsaredisabled.ThestatusandVCDIVoutputsallremainactive.Normalfunctionisfullyrestoredfromthepreviousstatewhenpauseends.
StatusOutputs
TheLTC4011open-drainstatusoutputsprovidevaluableinformation about the IC’s operating state and can beused foravarietyofpurposes inapplications.Table1summarizesthestateofthefourstatusoutputsandtheVCDIVpinasafunctionofLTC4011operation.Thestatusoutputscandirectlydrivecurrent-limitedLEDsterminatedtotheDCinput.TheVCDIVcolumninTable1isstrictlyinformational.VCDIVshouldonlybeusedfortheVCELLresistordivider,aspreviouslydiscussed.
Table1.LTC4011StatusPinsREADY FAULT CHRG TOC VCDIV CHARGERSTATE
Off Off Off Off Off Off
On Off Off Off On ReadytoCharge(VTEMPHeldLow)
orAutomaticRecharge
On Off On Off On PrechargeorFastCharge(MaybePaused)
On Off On On On NiMHTop-OffCharge(MaybePaused)
On On OnorOff OnorOff On TemperatureLimitsExceeded
Off On Off Off On FaultState(Latched)
LTC4011
��4011fb
operaTion
12
–
+
CC
EAITH
IPROG
R3
QPWM CLOCKS
R
R4
R1
BAT
11SENSE
RSENSE
15BGATE
17TGATE
LTC4011VCC
P
N
R2
4011 F02
Figure2.LTC4011PWMControlLoop
PWMCurrentSourceController
AnintegralpartoftheLTC4011isthePWMcurrentsourcecontroller. The chargeruses a synchronous step-downarchitecturetoproducehighefficiencyandlimitedthermaldissipation.Thenominaloperatingfrequencyof550kHzallowsuseofasmallerexternalfiltercomponents.TheTGATEandBGATEoutputshaveinternallyclampedvolt-ageswings.Theysourcepeakcurrentstailoredtosmallersurface-mountpowerFETslikelytoappearinapplicationsprovidinganaveragechargecurrentof3Aorless.Duringthevariouschargingstates,theLTC4011usesthePWMcontrollertoregulateanaveragevoltagebetweenSENSEandBATthatrangesfrom10mVto100mV.
AconceptualdiagramoftheLTC4011PWMcontrolloopisshowninFigure2.
The voltage across the external current programmingresistorRSENSEisaveragedbyintegratingerroramplifierEA.AninternalprogrammingcurrentisalsopulledfrominputresistorR1.TheIPROG•R1productestablishesthedesiredaveragevoltagedropacrossRSENSE,andhence,theaveragecurrent throughRSENSE.The ITHoutputoftheerroramplifierisascaledcontrolcurrentfortheinput
ofthePWMcomparatorCC.TheITH•R3productsetsapeakcurrentthresholdforCCsuchthatthedesiredaver-agecurrent throughRSENSE ismaintained.ThecurrentcomparatoroutputdoesthisbyswitchingthestateoftheSRlatchattheappropriatetime.
Atthebeginningofeachoscillatorcycle,thePWMclocksetstheSRlatchandtheexternalP-channelMOSFETisswitchedon(N-channelMOSFETswitchedoff)torefreshthecurrentcarriedbytheexternalinductor.Theinductorcurrent and voltage drop across RSENSE begin to riselinearly. During normal operation, the PFET is turnedoff(NFETon)duringthecyclebyCCwhenthevoltagedifferenceacrossRSENSEreachesthepeakvaluesetbytheoutputofEA.TheinductorcurrentthenrampsdownlinearlyuntilthenextrisingPWMclockedge.Thisclosestheloopandmaintainsthedesiredaveragechargecurrentintheexternalinductor.
LowDropoutCharging
Afterchargingisinitiated,theLTC4011doesnotrequirethatVCCremainatleast500mVaboveBATbecausesitu-ationsexistwherelowdropoutchargingmightoccur.Inoneinstance,parasiticseriesresistancemaylimitPWMheadroom (between VCC and BAT) as 100% charge isreached.AsecondcasecanarisewhentheDCadapterselectedbytheenduserisnotcapableofdeliveringthecurrentprogrammedbyRSENSE,causingtheoutputvolt-ageoftheadaptertocollapse.Whileinlowdropout,theLTC4011PWMrunsnear100%dutycyclewithafrequencythatmaynotbeconstantandcanbelessthan550kHz.Thechargecurrentwilldropbelowtheprogrammedvaluetoavoidgeneratingaudiblenoise,sotheactualchargedelivered to the battery may depend primarily on theLTC4011chargetimer.
InternalDieTemperature
TheLTC4011providesinternalovertemperaturedetectiontoprotectagainstelectricaloverstress,primarilyattheFETdriveroutputs.Ifthedietemperaturerisesabovethisthermallimit,theLTC4011stopsswitchingandindicatesafaultaspreviouslydiscussed.
LTC4011
��4011fb
applicaTions inForMaTionExternalDCSource
TheexternalDCpowersourceshouldbeconnectedtothechargingsystemandtheVCCpinthrougheitherapowerdiodeorP-channelMOSFET.Thispreventscatastrophicsystemdamageintheeventofaninputshorttogroundorreverse-voltagepolarityattheDCinput.TheLTC4011auto-maticallysenseswhenthisinputispresent.Theopen-circuitvoltageoftheDCsourceshouldbebetween4.5Vand34V,dependingonthenumberofcellsbeingcharged.Inordertoavoidlowdropoutoperation,ensure100%capacityatchargetermination,andallowreliabledetectionofbatteryinsertion,removalorovervoltage,thefollowingequationcanbeusedtodeterminetheminimumfull-loadvoltagethatshouldbeprovidedbytheexternalDCpowersource.
DCIN(MIN)=(n•2V)+0.3V
wherenisthenumberofseriescellsinthebatterypack.
The LTC4011 will properly charge over a wide rangeof DCIN and BAT voltage combinations. Operating theLTC4011inlowdropoutorwithDCINmuchgreaterthanBATwillforcethePWMfrequencytobemuchlessthan550kHz.TheLTC4011disableschargingandsetsafaultifalargeDCINtoBATdifferentialwouldcausegenerationofaudiblenoise.
PowerPathControl
ProperPowerPathcontrolisanimportantconsiderationwhenfastchargingnickelcells.Thiscontrolensuresthatthesystemloadremainspoweredatall times,butthatnormalsystemoperationandassociatedloadtransientsdonotadverselyaffectfastchargetermination.Forhighefficiencyandlowdropoutapplications,theLTC4011canprovidegatedrivefromtheINFETpindirectlytoaninputP-channelMOSFET.
Thebatteryshouldalsobeconnectedtotherawsystemsupply by a switch that selects the battery for systempoweronlyifanexternalDCsourceisnotpresent.Again,forapplicationsrequiringhigherefficiency,aP-channelMOSFETwithitsgatedrivenfromtheDCinputcanbeusedtoperformthisswitchingfunction(seeFigure8).GatevoltageclampingmaybenecessaryonanexternalPMOStransistorusedinthismannerathigherinputvoltages.Alternatively,adiodecanbeusedinplaceofthisFET.
BatteryChemistrySelection
ThedesiredbatterychemistryisselectedbyprogrammingtheCHEMpintothepropervoltage.IfitiswiredtoGND,a set of parameters specific to charging NiMH cells isselected.WhenCHEMisleftfloatingorconnectedtoVRT,chargingisoptimizedforNiCdcells.ThevariouschargingparametersaredetailedinTable2.
ProgrammingChargeCurrent
Charge current is programmed using the followingequation:
R
mVISENSEPROG
= 100
RSENSE is an external resistor connected between theSENSEandBATpins.A1%resistorwithalowtemperaturecoefficientandsufficientpowerdissipationcapabilitytoavoidself-heatingeffectsisrecommended.ChargerateshouldbebetweenapproximatelyC/2and2C.
InductorValueSelection
Formanyapplications,10µHrepresentsanoptimumvaluefortheinductorthePWMusestogeneratechargecurrent.For applicationswith IPROG of 1.5A or greater runningfromanexternalDCsourceof15Vorless,valuesbetween5µHand7.5µHcanoftenbeselected.Forwideroperatingconditionsthefollowingequationcanbeusedasaguideforselectingtheminimuminductorvalue.
L>6.5•10–6•VDCIN•RSENSE,L≥4.7µH
Actualpartselectionshouldaccountforbothmanufacturingtoleranceandtemperaturecoefficienttoensurethismini-mum.Agoodinitialselectioncanbemadebymultiplyingthecalculatedminimumby1.4androundingupordowntotheneareststandardinductancevalue.
Ultimately,thereisnosubstituteforbenchevaluationoftheselectedinductorinthetargetapplication,whichcanalsobeaffectedbyotherenvironmentalfactorssuchasambient operating temperature. Using inductor valueslowerthanrecommendedbytheequationshownabovecanresultinafaultconditionatthestartofprechargeortop-offcharge.
LTC4011
��4011fb
ProgrammingMaximumChargeTimes
ConnectingtheappropriateresistorbetweentheTIMERpinandGNDprogramsthemaximumdurationofvariouschargingstates.Tosomedegree,thevalueshouldreflecthowcloselytheprogrammedchargecurrentmatchesthe1Crateoftargetedbatterypacks.Themaximumfastchargeperiodisdeterminedbythefollowingequation:
SometypicaltimingvaluesaredetailedinTable3.RTIMERshouldnotbelessthan15k.TheactualtimelimitsusedbytheLTC4011havearesolutionofapproximately±30secondsinadditiontothetolerancesgiventheElectricalCharacteristicstable.Ifthetimerendswithoutavalid–∆Vor∆T/∆tchargetermination,thechargerentersthefaultstate.Themaximumtimeperiodisapproximately4.3hours.
CellVoltageNetworkDesign
Anexternal resistornetwork is required toprovide theaveragesingle-cellvoltagetotheVCELLpinoftheLTC4011.
ThepropercircuitformulticellpacksisshowninFigure3.TheratioofR2toR1shouldbeafactorof(n–1),wherenisthenumberofseriescellsinthebatterypack.ThevalueofR1shouldbebetween1kand100k.ThisrangelimitsthesensingerrorcausedbyVCELLleakagecurrentandpreventstheONresistanceoftheinternalNFETbe-tweenVCDIVandGNDfromcausingasignificanterrorintheVCELLvoltage.Theexternalresistornetworkisalsoused todetectbattery insertionandremoval.ThefilterformedbyC1andtheparallelcombinationofR1andR2
12
9
BAT
LTC4011 R2+
FOR TWO ORMORE SERIES CELLS
R1 C1
R2 = R1(n – 1)
4011 F03
VCDIV
GND
8
5
VCELL
Figure3.MulitpleCellVoltageDivider
applicaTions inForMaTionTable2.LTC4011ChargingParameters
STATECHEM
PINBAT
CHEMISTRY TIMER TMIN TMAX ICHRG TERMINATIONCONDITIONPC Both tMAX/12 5°C 45°C IPROG/5 TimerExpires
FC Open NiCd tMAX 5°C 60°C IPROG –20mVperCellor2°C/Minute
GND NiMH tMAX 5°C 60°C IPROG 1.5°C/MinuteforFirsttMAX/12MinutesifInitialVCELL<1.325V
–10mVperCellor1°C/MinuteAftertMAX/12MinutesorifInitialVCELL>1.325V
TOC GND NiMH tMAX/3 5°C 60°C IPROG/10 TimerExpires
AR Both 5°C 45°C 0 VCELL<1.325V
PC: PrechargeFC: FastCharge(Initial–∆VTerminationHoldOffoftMAX/12MinutesMayApply)TOC: Top-OffCharge(OnlyforNiMH∆T/∆tFCTerminationAfterInitialtMAX/12Period)AR: AutomaticRecharge(TemperatureLimitsApplytoStateTerminationOnly)
Table3.LTC4011TimeLimitProgrammingExamples
RTIMER
TYPICALFASTCHARGERATE
PRECHARGELIMIT(MINUTES)
FASTCHARGEVOLTAGESTABILIZATION
(MINUTES)FASTCHARGELIMIT
(HOURS)
TOP-OFFCHARGE
(MINUTES)24.9k 2C 3.8 3.8 0.75 15
33.2k 1.5C 5 5 1 20
49.9k 1C 7.5 7.5 1.5 30
66.5k 0.75C 10 10 2 40
100k C/2 15 15 3 60
LTC4011
��4011fb
applicaTions inForMaTion
Figure4.Single-CellMonitorNetwork
12
9
BAT
10k 10k
33nF
1 CELL
4011 F04
VCDIV
8VCELL
where:
R0=thermistorresistance(Ω)atT0
T0=thermistorreferencetemperature(°K)
β=exponentialtemperaturecoefficientofresistance
Forthermistorswithβlessthan3750,theequationforR3yieldsanegativenumber.ThisnumbershouldbeusedtocomputeR2,eventhoughR3isreplacedwithashortintheactualapplication.Anadditionalhightemperaturechargequalificationerrorofbetween0°Cand5°Cmayoccurwhenusingthermistorswithβ lowerthan3750.Thermistorswithnominalβlessthan3300shouldbeavoided.
Thefilter formedbyR4andC1 inFigure5 isoptionalbut recommended for rejecting PWM switching noise.Alternatively,R4maybereplacedbyashort,andavaluechosenforC1whichwillprovideadequatefilteringfromtheTheveninimpedanceoftheremainingthermistornet-work.Thefilterpolefrequency,whichshouldbelessthan500Hz,willvarymorewithbatterytemperaturewithoutR4.ExternalcomponentsshouldbechosentomaketheTheveninimpedancefromVTEMPtoGND100kΩorless,includingR4,ifpresent.
DisablingThermistorFunctions
TemperaturesensingisoptionalinLTC4011applications.For lowcost systemswhere temperature sensingmaynotberequired, theVTEMPpinmaysimplybewiredtoVRT todisable temperaturequalificationofallcharging
isrecommendedforrejectingPWMswitchingnoise.ThevalueofC1shouldbechosentoyielda1storderlowpassfrequencyoflessthan500Hz.Inthecaseofasinglecell,theexternalapplicationcircuitshowninFigure4isrec-ommendedtoprovidethenecessarynoisefilteringandmissingbatterydetection.
ThermistorNetworkDesign
The network for proper temperature sensing using athermistorwithanegativetemperaturecoefficient(NTC)isshowninFigure5.R3isonlypresentforthermistorswith an exponential temperature coefficient (β) above3750. For thermistors with β below 3750, replace R3withashort.
Figure5.ExternalNTCThermistorNetwork
6
7
VRT
R1
R2RT
R451k
R3
C110nF
4011 F05
VTEMP
TheLTC4011isdesignedtoworkbestwitha5%10KNTCthermistorwithaβnear3750,suchastheSiemens/EPCOSB57620C103J062.Inthiscase,thevaluesfortheexternalnetworkaregivenby:
R1=9.76k R2=28k R3=0Ω
However,theLTC4011willoperatewithotherNTCtherm-istors having different nominal values or exponentialtemperaturecoefficients.Forthesethermistors,thedesignequationsfortheresistorsintheexternalnetworkare:
LTC4011
��4011fb
applicaTions inForMaTionoperations.However,thispracticeisnotrecommendedforNiMHcellschargedwellaboveorbelowtheir1Crate,becausefastchargeterminationbasedsolelyonvoltageinflectionmaynotbeadequatetoprotectthebatteryfromasevereovercharge.Aresistorbetween10kand20kmaybeusedtoconnectVTEMPtoVRTifthepausefunctionisstilldesired.
INTVDDRegulatorOutput
IfBGATEisleftopen,theINTVDDpinoftheLTC4011canbeusedasanadditionalsourceofregulatedvoltageinthehostsystemanytimeREADYisactive.Switchingloadson INTVDDmay reduce theaccuracyof internalanalogcircuits used to monitor and terminate fast charging.Inaddition,DCcurrentdrawnfromtheINTVDDpincangreatlyincreaseinternalpowerdissipationatelevatedVCCvoltages.Aminimumceramicbypasscapacitorof0.1µFisrecommended.
CalculatingAveragePowerDissipation
TheusershouldensurethatthemaximumratedICjunctiontemperatureisnotexceededunderalloperatingconditions.The thermal resistance of the LTC4011 package (θJA)is38°C/W,provided theexposedmetalpad isproperlysolderedtothePCB.TheactualthermalresistanceintheapplicationwilldependontheamountofPCBcoppertowhichthepackageissoldered.Feedthroughviasdirectlybelow thepackage thatconnect to innercopper layersarehelpfulinloweringthermalresistance.Thefollowingformulamaybeusedtoestimatethemaximumaveragepower dissipation PD (in watts) of the LTC4011 undernormaloperatingconditions.
where:
IDD=AverageexternalINTVDDloadcurrent,ifany
IVRT=LoadcurrentdrawnbytheexternalthermistornetworkfromVRT,ifany
QTGATE=GatechargeofexternalP-channelMOSFETincoulombs
QBGATE=GatechargeofexternalN-channelMOSFET(ifused)incoulombs
VLED=MaximumexternalLEDforwardvoltage
RLED=ExternalLEDcurrent-limitingresistorusedintheapplication
n=NumberofLEDsdrivenbytheLTC4011
SampleApplications
Figures6 through9detailsamplechargerapplicationsofvariouscomplexities.CombinedwiththeTypicalAp-plicationonthefirstpageofthisdatasheet,theseFiguresdemonstrate some of the proper configurations of theLTC4011.MOSFETbodydiodesareshowninthesefiguresstrictlyforreferenceonly.
Figure6showsaminimumapplication,whichmightbeencountered in lowcostNiCd fastchargeapplications.FET-basedPowerPathcontrolallowsformaximuminputvoltage range from the DC adapter. The LTC4011 uses–∆V to terminate the fast charge state, as no externaltemperature information is available. NonsynchronousPWMswitchingisemployedtoreduceexternalcomponentcost.AsingleLEDindicateschargingstatus.
A3ANiMHapplicationofmediumcomplexityisshowninFigure7.PowerPathcontrolthatiscompletelyFET-basedallowsforbothminimuminputvoltageoverheadandmini-mumswitchoverlosswhenoperatingfromthebattery.
P-channelMOSFETQ4functionsasaswitchtoconnectthebatterytothesystemloadwhenevertheDCinputadapterisremoved.IfthemaximumbatteryvoltageislessthanthemaximumratedVGSofQ4,diodeD1andresistorR5are not required. Otherwise choose the Zener voltageofD1tobelessthanthemaximumratedVGSofQ4.R5providesabiascurrentof(VBAT–VZENER)/(R5+20k)forD1whentheinputadapterisremoved.ChooseR5tomakethiscurrent,whichisdrawnfromthebattery,justlargeenoughtodevelopthedesiredVGSacrossD1.
Precharge,fastchargeandtop-offstatesareindicatedbyexternalLEDs.TheVTEMPthermistornetworkallowstheLTC4011toaccuratelyterminatefastchargeunderavarietyofappliedchargerates.UseofasynchronousPWMtopol-ogyimprovesefficiencyandlowerspowerdissipation.
LTC4011
��4011fb
applicaTions inForMaTion
Figure7.3ANiMHChargerwithFullPowerPathControl
Figure6.Minimum1ALTC4011Application
0.1µF
10µF
10µF
10µH
FAULTINFET
CHRG
FROMADAPTER
12V
TOCREADY
0.033µF 0.068µF
20µF
0.1µF
4.7µH
20µF
FAULTCHRGTOCREADY
FROMADAPTER
12V
Afull-featured2ALTC4011applicationisshowninFigure8.FET-basedPowerPathallowsformaximuminputvoltagerangefromtheDCadapter.TheinherentvoltageratingsoftheVCELL,VCDIV,SENSEandBATpinsallowchargingofone tosixteenseriesnickel cells in thisapplication,governedonlybytheVCCoverheadlimitspreviouslydis-cussed.Theapplicationincludesallaveragecellvoltage
andbatterytemperaturesensingcircuitryrequiredfortheLTC4011toutilize its full rangeofchargequalification,safetymonitoringandfastchargeterminationfeatures.LED D1 indicates valid DC input voltage and installedbattery,whileLEDsD2andD3indicatecharging.LEDD4indicatesfaultconditions.ThegroundedCHEMpinselectstheNiMHchargeterminationparameterset.
LTC4011
�04011fb
applicaTions inForMaTion
Figure8.Full-Featured2ALTC4011Application
0.1µF
D1 D2 D3 D4
10µF
6.8µH
10µF
FROMADAPTER
12V
FAULTINFET
CHRGTOCREADY
Figure9.LTC4011withMCUInterface
0.1µF
10µF
22µH
NiMH PACKWITH 10k NTC(1Ahr)
FAULTCHRGTOCREADY
PAUSEFROMMCU
INFET
FROMADAPTER
24V
While theLTC4011 is a complete, standalonesolution,Figure9showsthat itcanalsobe interfaced toahostmicroprocessor.ThehostMCUcancontrolthechargerdirectlywithanopen-drainI/OportconnectedtotheVTEMPpin, if thatport is lowleakageandcantolerateat least
2V.ThechargerstateismonitoredonthefourLTC4011statusoutputs.ChargingofNiMHbatteriesisselectedinthisexample.However,NiCd(CHEM→VRT)parameterscouldbechosenaswell.
LTC4011
��4011fb
applicaTions inForMaTionUnlikealloftheotherapplicationsdiscussedsofar,thebatterycontinuestopowerthesystemduringcharging.TheMCUcouldbepowereddirectlyfromthebatteryorfromanytypeofpostregulatoroperatingfromthebattery.Inthisconfiguration,theLTC4011reliesexpresslyontheabilityofthehostMCUtoknowwhenloadtransientswillbeencountered.TheMCUshould thenpausecharging(andthus–∆Vprocessing)duringthoseeventstoavoidprematurefastchargetermination.IftheMPUcannotreli-ablyperformthisfunction,fullPowerPathcontrolshouldbeimplemented.Inmostapplications,thereshouldnotbeanexternalloadonthebatteryduringcharge.Excessivebatteryloadcurrentvariations,suchasthosegeneratedbyapost-regulatingPWM,cangeneratesufficientvoltagenoisetocausetheLTC4011toprematurelyterminateachargecycleand/orprematurelyrestartafastcharge.Inthiscase,itmaybenecessarytoinhibittheLTC4011aftercharging is completeuntil externalgasgaugecircuitryindicatesthatrechargingisnecessary.ShutdownpowerisappliedtotheLTC4011throughthebodydiodeofQ2inthisapplication.
Waveforms
Samplewaveforms forastandaloneapplicationduringatypicalchargecycleareshowninFigure10.Notethatthesewaveformsarenottoscaleanddonotrepresentthecompleterangeofpossibleactivity.ThefigureissimplyintendedtoallowbetterconceptualunderstandingandtohighlighttherelativebehaviorofcertainsignalsgeneratedbytheLTC4011duringatypicalchargecycle.
Initially, theLTC4011 is in lowpowershutdownas thesystemoperatesfromaheavilydischargedbattery.ADCadapteristhenconnectedsuchthatVCCrisesabove4.25Vandis500mVaboveBAT.TheREADYoutputisassertedwhentheLTC4011completeschargequalification.
WhentheLTC4011determineschargingshouldbegin,itstartsaprechargecyclebecauseVCELLislessthan900mV.As long as the temperature remains within prescribedlimits,theLTC4011charges(TGATEswitching),applyinglimitedcurrenttothebatterywiththePWMinordertobringtheaveragecellvoltageto900mV.
When the precharge state timer expires, the LTC4011begins fastcharge ifVCELL isgreater than900mV.The
PWM,chargetimerandinternalterminationcontrolaresuspendedifpauseisasserted(VTEMP<200mV),butallstatusoutputscontinuetoindicatechargingisinprogress.Thefastchargestatecontinuesuntiltheselectedvoltageortemperatureterminationcriteriaaremet.Figure10sug-geststerminationbasedon∆T/∆t,whichforNiMHwouldbeanincreasegreaterthan1°Cperminute.
BecauseNiMHchargingterminateddueto∆T/∆tandthefastchargecyclehadlastedmorethantMAX/12minutes,theLTC4011begins a top-off chargewith a current ofIPROG/10.Top-offisaninternallytimedchargeoftMAX/3minuteswith theCHRG andTOCoutputscontinuouslyasserted.
Finally,theLTC4011enterstheautomaticrechargestatewhere theCHRGandTOCoutputsaredeasserted.ThePWMisdisabledbutVCDIVremainsassertedtomonitorVCELL.ThechargetimerwillberesetandfastchargingwillresumeifVCELLdropsbelow1.325V.TheLTC4011entersshutdownwhentheDCadapterisremoved,minimizingcurrentdrawfromthebatteryintheabsenceofaninputpowersource.
WhilenotapartofthesamplewaveformsofFigure10,temperaturequalificationisanongoingpartofthecharg-ingprocess,ifanexternalthermistornetworkisdetectedbytheLTC4011.Shouldprescribedtemperaturelimitsbeexceededduringanyparticularchargingstate,chargingwouldbesuspendeduntilthesensedtemperaturereturnedtoanacceptablerange.
Battery-ControlledCharging
BecauseoftheprogrammingarrangementoftheLTC4011,itmaybepossibletoconfigureitforbattery-controlledcharging.Inthiscase,thebatterypackisdesignedtoprovidecustomizedinformationtoanLTC4011-basedcharger,allowingasingledesigntoserviceawiderangeofapplicationbatteries.Assumethechargerisdesignedtoprovideamaximumchargecurrentof800mA(RSENSE=125mΩ).Figure11showsa4-cellNiCdbatterypackforwhich800mArepresentsa0.75Crate.Whenconnectedtothecharger,thispackwouldprovidebatterytempera-tureinformationandcorrectlyconfigurebothfastchargeterminationparametersandtimelimitsfortheinternalNiCdcells.
LTC4011
��4011fb
applicaTions inForMaTion
Asecondpossibility is toconfigureanLTC4011-basedchargertoacceptbatterypackswithvaryingnumbersofcells.ByincludingR2oftheaveragecellvoltagedividernetworkshowninFigure3,battery-basedprogrammingof thenumberofseries-stackedcellscouldberealizedwithoutdefeatingLTC4011detectionofbatteryinsertionorremoval.Figure12showsa2-cellNiMHbatterypackthatprogramsthecorrectnumberofseriescellswhenitisconnectedtothecharger,alongwithindicatingchemistryandprovidingtemperatureinformation.
Anyofthesebatterypackchargecontrolconceptscouldbecombinedinavarietyofwaystoservicecustomapplicationneeds.Chargingparallelcellsisnotrecommended.
PCBLayoutConsiderations
To prevent magnetic and electrical field radiation andhighfrequencyresonantproblems,properlayoutofthecomponentsconnectedtotheLTC4011isessential.RefertoFigure13.Formaximumefficiency, theswitchnoderiseand fall timesshouldbeminimized.The followingPCBdesignprioritylistwillhelpensurepropertopology.LayoutthePCBusingthisspecificorder.
1. InputcapacitorsshouldbeplacedascloseaspossibletoswitchingFETsupplyandgroundconnectionswiththe shortest copper traces possible. The switchingFETsmustbeonthesamelayerofcopperastheinput
Figure11.NiCdBatteryPackwithTimeLimitControl
Figure10.ChargingWaveformsExample
(PAUSE)
READY
CHRG
TOC
7
1200mAhrNiCd CELLS
BATTERYPACK
VTEMP
4
CHEM
10
TIMER
NC66.5k
4011 F11
+
–
10kNTC
Figure12.NiMHBatteryPackIndicatingNumberofCells
7
1500mAhrNiMH CELLS
BATTERYPACK
VTEMP
8
VCELL
R2
4
CHEM
4011 F12
+
–
10kNTC
LTC4011
��4011fb
capacitors.Vias shouldnotbeused tomake theseconnections.
2. Place the LTC4011 close to the switching FETgateterminals, keeping the connecting traces short toproducecleandrivesignals.ThisrulealsoappliestoICsupplyandgroundpinsthatconnecttotheswitchingFETsourcepins.TheICcanbeplacedontheoppositesideofthePCBfromtheswitchingFETs.
3. Placetheinductor inputascloseaspossibletothedrainoftheswitchingFETs.Minimizethesurfaceareaoftheswitchnode.Makethetracewidththeminimumneededtosupporttheprogrammedchargecurrent.Usenocopperfillsorpours.Avoidrunningthecon-nectiononmultiplecopperlayersinparallel.Minimizecapacitancefromtheswitchnodetoanyothertraceorplane.
4. Placethechargecurrentsenseresistorimmediatelyadjacenttotheinductoroutput,andorientitsuchthatcurrentsensetracestotheLTC4011areshort.Thesefeedbacktracesneedtoberuntogetherasasinglepairwiththesmallestspacingpossibleonanygivenlayeronwhichtheyarerouted.LocateanyfiltercomponentonthesetracesnexttotheLTC4011,andnotatthesenseresistorlocation.
5. Placeoutputcapacitorsadjacenttothesenseresisitoroutputandground.
6. Outputcapacitorgroundconnectionsmustfeedintothesamecopperthatconnectstotheinputcapacitorgroundbeforetyingbackintosystemground.
7. Connectionof switchingground tosystemground,oranyinternalgroundplaneshouldbesingle-point.Ifthesystemhasaninternalsystemgroundplane,agoodwaytodothisistoclusterviasintoasinglestarpointtomaketheconnection.
8. RouteanaloggroundasatracetiedbacktotheLTC4011GNDpinbeforeconnectingtoanyotherground.Avoidusingthesystemgroundplane.AusefulCADtechniqueistomakeanaloggroundaseparategroundnetandusea0Ωresistortoconnectanaloggroundtosystemground.
9. Agoodruleof thumbforviacount inagivenhighcurrentpathistouse0.5Apervia.Beconsistentwhenapplyingthisrule.
10.Ifpossible,placeallthepartslistedaboveonthesamePCBlayer.
11.Copperfillsorpoursaregoodforallpowerconnec-tionsexceptasnotedaboveinRule3.Copperplanesonmultiplelayerscanalsobeusedinparallel.Thishelpswiththermalmanagementandlowerstracein-ductance,whichfurtherimprovesEMIperformance.
12.For best current programming accuracy, provide aKelvin connection from RSENSE to SENSE and BAT.SeeFigure14foranexample.
13.ItisimportanttominimizeparasiticcapacitanceontheTIMER,SENSEandBATpins.Thetracesconnectingthesepinstotheirrespectiveresistorsshouldbeasshortaspossible.
Figure13.HighSpeedSwitchingPath
4011 F13
VBAT
L1
VIN
HIGHFREQUENCY
CIRCULATINGPATH
BAT
SWITCH NODE
CIN
SWITCHING GROUND
COUTD1
Figure14.KelvinSensingofChargeCurrent
SENSE
4011 F14
DIRECTION OF CHARGING CURRENT
RSENSE
BAT
applicaTions inForMaTion
LTC4011
��4011fb
package DescripTion
FE20 (CB) TSSOP 0204
0.09 – 0.20(.0035 – .0079)
0° – 8°
0.25REF
RECOMMENDED SOLDER PAD LAYOUT
0.50 – 0.75(.020 – .030)
4.30 – 4.50*(.169 – .177)
1 3 4 5 6 7 8 9 10
111214 13
6.40 – 6.60*(.252 – .260)
3.86(.152)
2.74(.108)
20 1918 17 16 15
1.20(.047)MAX
0.05 – 0.15(.002 – .006)
0.65(.0256)
BSC0.195 – 0.30
(.0077 – .0118)TYP
2
2.74(.108)
0.45 ±0.05
0.65 BSC
4.50 ±0.10
6.60 ±0.10
1.05 ±0.10
3.86(.152)
MILLIMETERS(INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
NOTE:1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
SEE NOTE 4
4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT
6.40(.252)BSC
FEPackage20-LeadPlasticTSSOP(4.4mm)(ReferenceLTCDWG#05-08-1663)
ExposedPadVariationCB
LTC4011
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable.However,noresponsibilityisassumedforitsuse.LinearTechnologyCorporationmakesnorepresenta-tionthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
revision hisToryREV DATE DESCRIPTION PAGENUMBER
B 01/10 ChangestoTypicalApplicationUpdatedOrderInformationSectionChangestoElectricalCharacteristicsChangestoOperationSectionChangestoApplicationsInformation
ChangestoFigures6,7,8,9
12
2,3,412,13,1415,16,19,
21,2219,20
(RevisionhistorybeginsatRevB)
LTC4011
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Linear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7417(408)432-1900●FAX:(408)434-0507●www.linear.com LINEAR TECHNOLOGY CORPORATION 2005
LT 0110 REV B • PRINTED IN USA
PARTNUMBER DESCRIPTION COMMENTS
LT®1510 Constant-Voltage/Constant-CurrentBatteryCharger Upto1.5AChargeCurrentforLi-Ion,NiCdandNiMHBatteries
LT1511 3AConstant-Voltage/Constant-CurrentBatteryCharger HighEfficiency,MinimumExternalComponentstoFastChargeLithium,NiMHandNiCdBatteries
LT1513 SEPICConstant-orProgrammable-Current/Constant-VoltageBatteryCharger
ChargerInputVoltageMaybeHigher,EqualtoorLowerthanBatteryVoltage,500kHzSwitchingFrequency
LTC1760 SmartBatterySystemManager AutonomousPowerManagementandBatteryChargingforTwoSmartBatteries,SMBusRev1.1Compliant
LTC1960 DualBatteryCharger/SelectorwithSPI 11-BitV-DAC,0.8%VoltageAccuracy,10-BitI-DAC,5%CurrentAccuracy
LTC4008 HighEfficiency,ProgrammableVoltage/CurrentBatteryCharger
Constant-Current/Constant-VoltageSwitchingRegulator,ResistorVoltage/CurrentProgramming,ACAdapterCurrentLimitandThermistorSensorandIndicatorOutputs
LTC4010 HighEfficiencyStandaloneNickelBatteryCharger CompleteNiMH/NiCdChargerinaSmall16-PinPackage,Constant-CurrentSwitchingRegulator
LTC4060 StandaloneLinearNiMH/NiCdFastCharger CompleteNiMH/NiCdChargerinaSmallLeadedorLeadless16-PinPackage,NoSenseResistororBlockingDiodeRequired
LTC4100 SmartBatteryChargerController Level2ChargerOperateswithorwithoutMCUHost,SMBusRev.1.1Compliant
LTC4150 CoulombCounter/BatteryGasGauge HighSideSenseofChargeQuantityandPolarityina10-PinMSOP
LTC4411 2.6ALowLossIdealDiode NoExternalMOSFET,AutomaticSwitchingBetweenDCSources,Simplified,140mΩOnResistance,ThinSOT™Package
LTC4412/LTC4412HV
LowLossPowerPathControllers VeryLowLossReplacementforPowerSupplyORingDiodesUsingMinimalExternalComponents,3V≤VIN≤28V,(3V≤VIN≤36VforHV)
LTC4413 Dual2.6A,2.5Vto5.5V,IdealDiodes LowLossReplacementforORingDiodes,100mΩOnResistance
ThinSOTisatrademarkofLinearTechnologyCorporation.
relaTeD parTs