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.