Features
➤ Conservative and repeatable
measurement of available charge
in rechargeable batteries
➤ Charge control output
➤ Designed for battery pack integration
- 120μA typical standby current
(self-discharge estimation mode)
- Small size enables implementations
in as little as 1
2
square inch of PCB
➤ Integrate within a system or as a
stand-alone device
- Display capacity via singlewire
serial communication
port or direct drive of LEDs
➤ Measurements compensated for
current and temperature
➤ Self-discharge compensation using
internal temperature sensor
➤ 16-pin narrow SOIC

General Description
The bq2012 Gas Gauge IC is intended
for battery-pack or in-system
installation to maintain an accurate
record of available battery charge.
The IC monitors a voltage drop
across a sense resistor connected in
series between the negative battery
terminal and ground to determine
charge and discharge activity of the
battery.
Self-discharge of NiMH and NiCd
batteries is estimated based on an
internal timer and temperature sensor.
Compensations for battery temperature
and rate of charge or discharge
are applied to the charge,
discharge, and self-discharge calculations
to provide available charge
information across a wide range of
operating conditions. Battery capacity
is automatically recalibrated, or
“learned,” in the course of a discharge
cycle from full to empty.
The bq2012 includes a charge control
output that, when used with
other full-charge safety termination
methods, can provide a cost-effective
means of controlling charge based
on the battery's charge state.
Nominal available charge may be directly
indicated using a five- or sixsegment
LED display. These segments
are used to graphically indicate
nominal available charge.
The bq2012 supports a simple
single-line bidirectional serial link to
an external processor (common
ground). The bq2012 outputs battery
information in response to external
commands over the serial link.
Internal registers include available
charge, temperature, capacity, battery
ID, battery status, and programming
pin settings. To support subassembly
testing, the outputs may also be controlled.
The external processor may
also overwrite some of the bq2012 gas
gauge data registers.
The bq2012 may operate directly
from three or four cells. With the
REF output and an external transistor,
a simple, inexpensive regulator
can be built to provide VCC across a
greater number of cells.