Pb-Acid Battery State-of-Charge Indicator - TI.com

1 OCTOBER 2010bq78412 Pb-Acid Battery State-of-Charge Indicator With Run- time DisplayCheck for Samples:bq784121 FEATURESDESCRIPTION Designed for Use with 12-V Lead-AcidThe bq78412 Pb-Acid Battery State-of-Charge (SoC)Batteries in Consumer UPS SystemsIndicator with Run- time Display is a completestand-alone Battery gas-gauge solution designed for Programmable Cell Models for Enhancedsingle 12V Pb-Acid batteries. The bq78412 displaysPb-Acid Gas Gauging Performanceremaining Run- time -To-Empty during discharge and Provides 10-LED Bar Graph of Run-TimePercent (%) capacity during charge using a 10-LEDR emaining During Discharge and % Capacity(light-emitting diode) bar ChargeThe bq78412 monitors Battery voltage, current, and Can Be Easily Integrated Into Battery Coverambient temperature to calculate State-of-Charge and Works with Pb-Acid Batteries Up to 327 Ahdetermine remaining runtime-to-empty.

2 Measuredvalues can be recorded and tracked for later retrieval Records Cumulative Usage Data Internally forfor warranty Return Analysis On-Chip Temperature SensorProgrammable cell models allow the bq78412 to becustomized to a variety of Pb-Acid formulations and Data Interface for Retrieving measurements and Coulomb-counting for Fully Programmable Features and Thresholdsgas-gauging are also automatically performed by thevia UART Serial Interfacebq78412. Current measurements use a small value State-of-Health (SoH) Determination andsense resistor placed in the negative power path andStatus , Includes Configurable Signal for Audiblecontinuous, real- time calculation of Battery capacityand run- time -to-empty , Low-Voltage, and OvervoltageWarningsTemperature sensing augments gas-gauge and Addressable Commands for Use incapacity information using a firmware algorithm toMulti- Battery Systemscompensate for the temperature effects on capacity.

3 Optional Infra-Red Communications InterfaceA serial port is available for configuring variousprogrammable parameters including cell models,APPLICATIONS calibration values, serial number and date ofmanufacture. The serial port can operate an infra-red Stand-Alone Uninterruptible Power Supplies(IR) interface to allow connector-less data acquisition. 12-V Pb-Acid Battery MonitorsThebq78412iseasilyconfigurable,i sfully Battery Warranty Data Logging Equipmentprogrammed and requires no algorithm or firmwaredevelopment1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of TexasInstruments semiconductor products and disclaimers thereto appears at the end of this data DATA information is current as of publication 2010, Texas Instruments IncorporatedProducts conform to specifications per the terms of the TexasInstruments standard warranty.

4 Production processing does notnecessarily include testing of all Recommended For New Designsbq78412 SLUSAA0 OCTOBER devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foamduring storage or handling to prevent electrostatic damage to the MOS MAXIMUM RATINGS(1)VALUEPARAMETERUNITSMINMAXV oltage applied to VBAT+ applied to VS (VRS+ VRS ) 2626 VVoltage applied toRS+, RS Common mode (VRS+, VRS ) applied to AVDD and DVDD applied to other pins(2) + current at any device terminal 22mA(1) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods maydegrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyondthose specified is not implied.

5 (2) VDD refers to voltage on DVDD and AVDD OPERATING CONDITIONSMINTYPMAXUNITSS upply voltageVBAT+41226 VOperating temperature 4085 CBattery capacity150327 AhrCurrent measurement, average 100100 ACurrent measurement, peak 320300 AMEASUREMENT ACCURACY (12-V Battery )PARAMETERMINTYPMAXUNITB attery voltage measurement(1) 1%Shunt voltage measurement(2) 1%Temperature measurement(3) 1 CTiming accuracy of internal clock(4) (RTTE)(5) 15min(1) Specified at 12 V.(2) Specified at full scale.(3) Offset calibration of the temperature takes place prior to this measurement(4) Calibrated clock frequency, tolerance over temperature 0 C to +85 C(5) Capacity learning is done prior to COMMUNICATIONS PORT TIMINGMINTYPMAXUNITSData rate9600 orBaud1200 Command response time (1)100msTransmit intercharacter interval(2)4ms(1) Maximum time from host transmission of last command byte to first response by the device.

6 (2) Maximum time interval between start bits for data or response being transmitted from the Documentation FeedbackCopyright 2010, Texas Instruments IncorporatedProduct Folder Link(s):bq78412 Not Recommended For New Designs123456789101112131415161718192021 22N/CSCLKSDATN/CSDASCLSDAVDDN/CN/CN/CBUZ ZERRXDTXDAVSSVSRS N/CRS+N/CA0A1 DDW Package(Top View)RST_NXINXOUTDVSSRSVDDVDDTEST5 TEST4 TEST3 TEST2 TEST1N/CDISPENRSVDN/CAVSSREG33N/CN/CVBAT + OCTOBER 2010 CURRENT CONSUMPTIONOPERATING MODETYPICAL (mA) to UPS and gas gauging active. Display is active and not connected to UPS. Display is active and not connected. Display CHARACTERISTICSPARAMETERCONDITIONSMINTYP MAXUNIT100 A ILOAD 100 mA, TJ= 25 load regulation100 A ILOAD 100 mA, 40 C TJ 85 basic resolution12bitsSense voltage measurement step size4mVShunt current measurement step scale current sense voltage range 160mVSense resistor1m Package pad is on the bottom side of the = no connectCopyright 2010, Texas Instruments IncorporatedSubmit Documentation Feedback3 Product Folder Link(s):bq78412 Not Recommended For New Designsbq78412 SLUSAA0 OCTOBER DESCRIPTIONSbq78412I/ input.

7 Connect to input. Connect to power to the analog logic. Typically connected to to output. Active high when alarm condition is high output, turns on display enable transistor. Not required in all applications. Blanks display supply to the digital logic. Connect a F capacitor to VSS. Typically connected to to groundREG3328 PRegulated power to external RC network for power-up Reserved, no connection 17 ICurrent sense negativeRS+18 ICurrent sense positiveRXD9 IUART RX data6OI2C clock outputSCL24II2C clock for internal use. Connect to SCL pin transition clocks data into external serial in, parallel out shift XCVR Shutdown; HIGH=XCVR in shutdown, LOW=XCVR Active5I/OI2C dataSDA23I/OI2C data for internal use. Connect to SDA pin display data to serial in, parallel out shift register.

8 A low bit turns on an pin, no connectionTEST235I/OTest pin, no connectionTEST336I/OTest pin, no connectionTEST437I/OTest pin, no connectionTEST538I/OTest pin, no connectionTXD8 OUART TX dataVBAT+25 PInput to internal voltage. Connect to Battery terminal of 8-MHz crystal oscillator or crystal pin. (Optional: Can be left unconnected to use internalXIN43 Ioscillator)Output terminal of 8-MHz crystal oscillator or crystal pin. (Optional: Can be left unconnected to use internalXOUT42 Ooscillator)14111213N/C No connection19202627334 Submit Documentation FeedbackCopyright 2010, Texas Instruments IncorporatedProduct Folder Link(s):bq78412 Not Recommended For New Designs12893456Q0Q1Q2Q3 ABCLKCLRSN74HC164147 VCCGND101112Q4Q5Q613Q7470W(x 16)GRNGRNGRNGRNYELYELYELREDLED9 LED8 LED7 LED6 LED5 LED4 LED3 LED2 SDATSCLK12893456Q0Q1Q2Q3 ABCLKCLRSN74HC164147 VCCGND101112Q4Q5Q613Q7 REDREDREDYELGRNGRNGRNGRNLED1 LED0 ReplaceWarnGoodChargeDischargeFullRTTE Status / %SoCSoH StatusMMBT3904 MMBT3904416151432 VSAVSSAVDDDISPENN/Cbq78412 DDW3132 RSVDSDATSCLK1N/C11N/C1213N/CN/C4043 RSVDXIN42 XOUT3033N/CN/C17RS 10 kW47 kW18RS+2221A1A024 SCL23 SDAUDG-100841089 BUZZERTXDRXD7 SD445 RST_NSDA6 SCL39 DVDD28 REG33 VCC25 VBAT+10 V41 DVSS29 AVSS47 kW1 kWVCCMMBT390419 N/C20 N/C2627N/CN/C1Wt o kW100 WCF(1)RS1mW/2W+ V10W10W+ OCTOBER 2010 TYPICAL APPLICATION(1)

9 CF= F to 1 FCopyright 2010, Texas Instruments IncorporatedSubmit Documentation Feedback5 Product Folder Link(s):bq78412 Not Recommended For New Designsbq78412 SLUSAA0 OCTOBER INFORMATIONO verviewThe bq78412 is a complete Pb-Acid gas-gauge with a run- time display and warranty information storage. Itsupports large batteries up to a maximum capacity of 327 Ahr when measured at the 20 hour inputs include the 12-V nominal Battery voltage and the Battery current. Coulomb counting ondischarge and charge allows a State-of-Charge calculation and run- time -to-empty on discharge usage information is periodically and permanently stored internally and may be retrieved only by aspecial sequencing operation performed by the of the bq78412 requires no user interaction.

10 During charge and discharge, the LED display isautomatically activated when charge or discharge current is detected above a configurable Sense, Battery Voltage, Temperature, and time MeasurementsThe bq78412 measures charge and discharge current using a low-value (between 1 and 3 m ) sense resistorplaced in the negative power path of the circuit. This sense resistor may be as simple as a piece of thermallystable metal or the lead power post on the Battery itself. Calibration of this sense resistor is required in circuit (inmodule). The printed circuit board (PCB) designer must consider the impact of drift and/or variation in the senseresistor value over time and temperature, including self-heating temperature effects. The bq78412 does notcompensate for such voltage measured between the RS+ and RS pins is scaled by the sense resistor value (set inMeasScaleparameter) to calculate the current value.