Lead-Acid Fast-Charge IC datasheet - Texas …

1 Features Conforms to battery manufactur-ers' charge recommendations forcyclic and float charge Pin-selectable charge algorithms-Two-Step Voltage withtemperature-compensatedconstant-volt age maintenance-Two-Step Current withconstant-rate pulsed currentmaintenance-Pulsed Current: hysteretic,on-demand pulsed current Pin-selectable charge terminationby maximum voltage, 2V, mini-mum current, and maximumtime Pre-charge qualification detectsshorted, opened, or damaged cellsand conditions battery Charging continuously qualified bytemperature and voltage limits Internal temperature-compen-sated voltage reference Pulse-width modulation control-Ideal for high-efficiencyswitch-mode power conversion-Configurable for linear orgated current use Direct LED control outputs dis-play charge status and fault con-ditionsGeneral DescriptionThe bq2031 Lead-Acid fast ChargeIC is designed to optimize chargingof Lead-Acid chemistry batteries. Aflexible pulse-width modulationregulator allows the bq2031 to con-trol constant-voltage, constant-current, or pulsed-current regulator frequency is set by anexternal capacitor for design flexi-bility.

2 The switch-mode design keepspower dissipation to a minimum forhigh charge current charge cycle begins when power isapplied or the battery is safety, charging is inhibited un-til the battery voltage is within con-figured limits. If the battery voltage isless than the low-voltage threshold,the bq2031 provides trickle-currentcharging until the voltage rises intothe allowed range or an internaltimer runs out and places thebq2031 in a Fault condition. Thisprocedure prevents high-currentcharging of cells that are possiblydamaged or reversed. Charging isinhibited anytime the temperatureof the battery is outside the config-urable, allowed range. All voltagethresholds are bq2031 terminates fast (bulk)charging based on the following: Maximum voltage Second difference of cell voltage( 2V) Minimum current (in constant-voltage charging) Maximum time-out (MTO)After bulk charging, the bq2031 pro-vides temperature-compensatedmaintenance (float) charging tomaintain battery Fast-Charge ICTMTOTime-out timebase inputFLOATS tate control outputBATB attery voltage inputVCOMPV oltage loop comp inputICOMPC urrent loop comp inputIGSELC urrent gain select inputSNSS ense resistor inputTSTemperature sense inputTPWMR egulator timebase NarrowDIP or SOIC234 5678161514131211109 LED2/DSELLED1/TSELMODVCCVSSCOMLED3/QSELT PWMTMTOFLOATBATVCOMPICOMPIGSELSNSTSLED3/ Charge status output 3/QSELC harge algorithm selectinput 1 COMC ommon LED outputVSSS ystem 10% powerMODM odulation controloutputLED1/Charge status output 1/TSELC harge algorithm selectinput 2 LED2/Charge status output 2/DSELD isplay select inputPin ConnectionsPin NamesSLUS156 JUNE 1999 Ebq2031 Not Recommended for New Designs (NRND)

3 Pin DescriptionsTMTOTime-out timebase inputThis input sets the maximum charge resistor and capacitor values are deter-mined using equation 6. Figure 9 shows theresistor/capacitor state control outputThis open-drain output uses an external re-sistor divider network to control the BAT in-put voltage threshold (VFLT) for the floatcharge regulation. See Figure voltage inputBAT is the battery voltage sense input. This po-tential is generally developed using a high-impedance resistor divider network connectedbetween the positive and the negative terminalsof the battery. See Figure 6 and equation loop compensation inputThis input uses an external C or R-C net-work for voltage loop gain select inputThis three-state input is used to set IMIN forfast charge termination in the Two-StepVoltage algorithm and for maintenance cur-rent regulation in the Two-Step Current al-gorithm. See Tables 3 and loop compensation inputThis input uses an external C or R-C net-work for current loop current sense inputBattery current is sensed via the voltage de-veloped on this pin by an external sense re-sistor, RSNS, connected in series with the lowside of the battery.

4 See equation sense inputThis input is for an external battery tem-perature monitoring thermistor or probe. Anexternal resistor divider network sets thelower and upper temperature Figures 7 and 8 and equations 4 and timebase inputThis input uses an external timing capacitorto ground the pulse-width modulation(PWM) frequency. See equation LED outputCommon output for LED1 3. This output isin a high-impedance state during initiali-zation to read program inputs on TSEL,QSEL, and regulation select inputWith TSEL, selects the charge Table control outputMOD is a pulse-width modulated push/pulloutput that is used to control the chargingcurrent to the battery. MOD switches highto enable current flow and low to inhibit cur-rent 3 Charger display status 1 3 outputsThese charger status output drivers are forthe direct drive of the LEDdisplay. Displaymodes are shown in Table 2. These outputs aretri-stated during initialization so that QSEL,TSEL, and DSEL can be select inputThis three-level input controls the LED1 3charge display modes.

5 See Table select inputWith QSEL, selects the charge Table , 10% powerVSSG roundFunctional DescriptionThe bq2031 functional operation is described in terms of:nCharge algorithmsnCharge qualificationnCharge status displaynVoltage and current monitoringnTemperature monitoring2bq2031 Not Recommended for New Designs (NRND)nFast charge terminationnMaintenance chargingnCharge regulationCharge AlgorithmsThree charge algorithms are available in the bq2031:nTwo-Step VoltagenTwo-Step CurrentnPulsed CurrentThe state transitions for these algorithms are describedin Table 1 and are shown graphically in Figures 2through 4. The user selects a charge algorithm by con-figuring pins QSEL and QualificationThe bq2031 starts a charge cycle when power is appliedwhile a battery is present or when a battery is 1 shows the state diagram for pre-charge qualifi-cation and temperature monitoring. The bq2031 firstchecks that the battery temperature is within the al-lowed, user-configurable range.

6 If the temperature isout-of-range (or the thermistor is missing), the bq2031enters the Charge Pending state and waits until the bat-tery temperature is within the allowed range. ChargePending is annunciated by OutputTwo-Step VoltageLH/LNote 1-- fast charge, phase 1while VBAT<VBLK,ISNS=IMAXC urrent regulationFast charge, phase 2while ISNS>IMIN,VBAT=VBLKV oltage regulationPrimary terminationISNS=IMINM aintenanceVBAT=VFLTV oltage regulationTwo-Step CurrentHL-- fast chargewhile VBAT<VBLK,ISNS=IMAXC urrent regulationPrimary terminationVBAT=VBLKor 2V < -8mVNote 2 MaintenanceISNS pulsed to average IFLTF ixed pulse currentPulsed CurrentHH-- fast chargewhile VBAT<VBLK,ISNS=IMAXC urrent regulationPrimary terminationVBAT=VBLKM aintenanceISNS=IMAX after VBAT=VFLT;ISNS= 0 after VBAT=VBLKH ysteretic pulsedcurrentNotes:1. May be high or low, but do not A Unitrode proprietary algorithm for accumulating successive differences between samples of 1. bq2031 Charging AlgorithmsChip OnVCC OnBatteryStatus?

7 Temperaturein RangeTemperature Outof Range orThermistor AbsentVoltageRegulation@ VFLT + = 1 MOD = 0 ChargePendingLED3 FlashMOD = 0 CurrentRegulation@ICONDT emperature Outof Range orThermistor AbsentTemperature InRange, Returnto Original StateVCELL < VLCO orVCELL > VHCOVCELL VLCO orFail:t = tQT1 orVCELL > VHCOP resentVLCO < VCELL < VHCOISNS < ICONDVCELL < 1 VCELL VHCOPASS: ISNS ICOND>Test 2 PASS: VCELL VMIN>FastChargeVCELL < VMINT erminationFail:t = tQT2 orVCELL < VLCO orVCELL > VHCOA bsentVCELL < VLCO orVCELL > VHCOF igure 1. Cycle Start/BatteryQualification State DiagramNot Recommended for New Designs (NRND)Thermal monitoring continues throughout the chargecycle, and the bq2031 enters the Charge Pending stateanytime the temperature is out of range. (There is oneexception; if the bq2031 is in the Fault state see be-low the out-of-range temperature is not recognized un-til the bq2031 leaves the Fault state.) All timers aresuspended (but not reset) while the bq2031 is in ChargePending.

8 When the temperature comes back into range,the bq2031 returns to the point in the charge cyclewhere the out-of-range temperature was the temperature is valid, the bq2031 performs twotests on the battery. In test 1, the bq2031 regulates a voltageof VFLT+ across the battery and observes not rise to at least ICOND within a time-out period ( ,the cell has failed open), the bq2031 enters the Fault state. Iftest 1 passes, the bq2031 then regulates current to ICOND(=IMAX/5) and watches VCELL(= VBAT-VSNS). If VCELL doesnot rise to at least VFLT within a time-out period ( , the cellhas failed short), again the bq2031 enters the Fault state. Ahold-off period is enforced at the beginning of qualificationtest 2 before thebq2031 recognizes its pass criterion. If thissecond test passes, the bq2031 begins fast (bulk) in the Fault state, the bq2031 waits until VCCis cy-cled or a battery insertion is detected. It then starts a newcharge cycle and begins the qualification process Status DisplayCharge status is annunciated by the LED driver outputsLED1 LED3.

9 Three display modes are available in the bq2031;the user selects a display mode by configuring pin DSEL. Table2 shows the three modes and their programming bq2031 does not distinguish between an over-voltagefault and a battery absent condition. The bq2031 entersthe Fault state, annunciated by turning on LED3, when-ever the battery is absent. The bq2031, therefore, gives anindication that the charger is on even when no battery isin place to be Action StateLED1 LED2 LED3 DSEL = 0(Mode 1)Battery absent or over-voltage faultLowLowHighPre-charge qualificationFlashLowLowFast chargingHighLowLowMaintenance chargingLowHighLowCharge pending (temperature out of range)XXFlashCharging faultXXHighDSEL = 1(Mode 2)Battery absent or over-voltage faultLowLowHighPre-charge qualificationHighHighLowFast chargeLowHighLowMaintenance chargingHighLowLowCharge pending (temperature out of range)XXFlashCharging faultXXHighDSEL = Float(Mode 3)Battery absent or over-voltage faultLowLowHighPre-charge qualificationFlashFlashLowFast charge: current regulationLowHighLowFast charge: voltage regulationHighHighLowMaintenance chargingHighLowLowCharge pending (temperature out of range)XXFlashCharging faultXXHighNotes:1 = VCC; 0 = VSS; X = LED state when fault occurred.

10 Flash =16s low,16s the Pulsed Current algorithm, the bq2031 annunciates maintenance when charging current is off andfast charge whenever charging current is 2. bq2031 Display Output SummaryNot Recommended for New Designs (NRND)5bq2031 IFLTIMINICONDIMAXC urrentVoltageVMINVFLTVBLKTimePhase 1 fast ChargePhase 2 CurrentVoltageMaintenanceQualificationFi gure 2. Two-Step Voltage AlgorithmICONDIMAXC urrentVoltageVMINVFLTVBLKTimeFast ChargeMaintenanceQualificationCurrentVol tageFigure 3. Two-Step Current AlgorithmICONDIMAXC urrentVoltageVMINVFLTVBLKTimeFast ChargeMaintenanceQualificationCurrentVol tageFigure 4. Pulsed Current AlgorithmNot Recommended for New Designs (NRND)Configuring Algorithm and DisplayModesQSEL/LED3, DSEL/LED2, and TSEL/LED1are bi-directional pins with two functions; they are LED driverpins as outputs and programming pins for the bq2031 asinputs. The selection of pull-up, pull-down, or no pull re-sistor programs the charging algorithm on QSEL andTSEL per Table 1 and the display mode on DSEL perTable 2.