BQ2063_15 Datasheet, PDF (6/60 Pages) Texas Instruments – SBS v1.1-COMPLIANT Li-ION GAS-GAUGE IC

bq2063
Not Recommended For New Designs
SBS v1.1ĆCOMPLIANT LiĆION GASĆGAUGE IC
WITH PROTECTOR INTERFACE
SLUS468E− MAY 2001 − REVISED APRIL 2002
functional description
general operation
The bq2063 determines battery capacity by monitoring the amount of charge input or removed from a
rechargeable battery. In addition to measuring charge and discharge, the bq2063 measures battery voltage,
temperature, and current, estimates battery self-discharge, and monitors the battery for low-voltage thresholds.
The bq2063 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 bq2063 accepts an NTC thermistor (Semitec 103AT) for temperature measurement or can be configured
for internal IC measurement. The bq2063 uses temperature to monitor battery pack and to compensate the
self-discharge estimate.
measurements
The bq2063 uses a fully differential, dynamically balanced voltage-to-frequency converter (VFC) for charge
measurement and a sigma delta analog-to-digital converter (ADC) for battery voltage, current, and temperature
measurement.
Voltage, current, and temperature measurements are made every 2−2.2 seconds, depending on the bq2063
operating mode. Maximum times occur with compensated EDV, mWh mode, and maximum allowable
discharge rate. Any AtRate computations requested or scheduled (every 20 seconds) may add up to 0.5
seconds to the time interval.
charge and discharge counting
The VFC 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 Figure 13. The VFC measures bipolar signals up to 250 mV. The
bq2063 detects charge activity when V_SR = V_(SR2)–V_(SR1) is positive and discharge activity when
V_SR = V_(SR2)–V_(SR1) is negative. The bq2063 continuously integrates the signal over time using an internal
counter. The fundamental rate of the counter is 6.25 µVh.
offset calibration
The bq2063 provides an auto-calibration feature to cancel the voltage offset error across SR₁ and SR₂ for
maximum charge measurement accuracy. The calibration routine is initiated by issuing a command to
ManufacturerAccess( ). The bq2063 is capable of automatic offset calibration down to 6.25µV. Offset
cancellation resolution is less than 1 µV.
digital filter
The bq2063 does not measure charge or discharge counts below the digital filter threshold. The digital filter
threshold is programmed in the EEPROM 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 bq2063 monitors the battery-pack
potential and the individual cell voltages through the VCELL pin. The bq2063 measures the voltage of three or
four series elements in a battery pack. CTL3 and CTL4 signal the S-8243 to present the cell voltages at the
VCELL input of the bq2063 according to Table 11. The bq2063 calculates the pack voltage and reports the result
in Voltage( ). The individual cell voltages are stored in the optional manufacturer function area.
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