BQ2083-V1P3 Datasheet, PDF (8/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2083-V1P3
SLVS508 − OCTOBER 2003
www.ti.com
FUNCTIONAL DESCRIPTION
General Operation
The bq2083−V1P3 determines battery capacity by monitoring the amount of charge input or removed from a
rechargeable battery. In addition to measuring charge and discharge, the bq2083−V1P3 measures battery voltage,
temperature, and current, estimates battery self-discharge, and monitors the battery for low-voltage thresholds. The
bq2083−V1P3 measures charge and discharge activity by monitoring the voltage across a small-value series sense
resistor between the battery’s negative terminal and the negative terminal of the battery pack. The available battery
charge is determined by monitoring this voltage and correcting the measurement for environmental and operating
conditions.
The bq2083−V1P3 interfaces with the bq29311 to perform battery protection, cell balancing and voltage translation
functions.
The bq2083−V1P3 can accept any NTC thermistor (default is Semitec 103AT) for temperature measurement or can
be configured to use its internal temperature sensor. The bq2083−V1P3 uses temperature to monitor the battery pack
and to compensate the self-discharge estimate.
Measurements
The bq2083−V1P3 uses an integrating sigma-delta analog-to-digital converter (ADC) for current measurement and
a second sigma delta ADC for battery voltage and temperature measurement. Voltage, current, and temperature
measurements are made every second.
Charge and Discharge Counting
The integrating ADC measures the charge and discharge flow of the battery by monitoring a small-value sense
resistor between the SR1 and SR2 pins as shown in the schematic. The integrating ADC measures bipolar signals
from −0.3 to 1.0 V. The bq2083−V1P3 detects charge activity when V_SR = V_(SR1)–V_(SR2) is positive and discharge
activity when V_SR = V_(SR1)–V_(SR2) is negative. The bq2083−V1P3 continuously integrates the signal over time, using
an internal counter. The fundamental rate of the counter is 2.6 nVh. The bq2083−V1P3 updates Remaining
Capacity() with the charge or discharge accumulated in this internal counter once every second.
Offset Calibration
The bq2083−V1P3 provides an autocalibration feature to cancel the voltage offset error across SR₁ and SR₂ for
maximum charge measurement accuracy. The bq2083−V1P3 performs autocalibration when the SMBus lines stay
low for a minimum of 20 s. The bq2083−V1P3 is capable of automatic offset calibration down to 1µV.
Digital Filter
The bq2083−V1P3 does not measure charge or discharge counts below the digital filter threshold. The digital filter
threshold is programmed in the Digital Filter DF 0x2b and should be set sufficiently high to prevent false signal
detection with no charge or discharge flowing through the sense resistor.
Voltage
While monitoring SR1 and SR2 for charge and discharge currents, the bq2083−V1P3 monitors the individual series
cell voltages through the bq29311. The bq2083−V1P3 configures the bq29311 to present the selected cell to the
VCELL pin of the bq29311 which should be connected to VIN of the bq2083−V1P3. The internal ADC of the
bq2083−V1P3 then measures the voltage and scales it appropriately. The bq2083−V1P3 then reports the Voltage( )
and the individual cell voltages in VCELL1, VCELL2, VCELL3, and VCELL4 located in 0x3c−0x3f.
Current
The bq2083−V1P3 uses the SR1 and SR2 inputs to measure and calculate the battery charge and discharge current
as represented in the data register Current().
Temperature
The TS input of the bq2083−V1P3 in conjunction with an NTC thermistor measures the battery temperature as shown
in the schematic. The bq2083−V1P3 reports temperature in Temperature( ).
The bq2083−V1P3 can also be configured to use its internal temperature sensor by setting the IT bit in Misc
Configuration DF 0x2a. Data flash locations DF 0xa4 through DF 0xad also have to be changed to prescribed values
if the internal temperature sensor option is selected.
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