特性 Features

? Conservative and repeatable

measurement of available charge

in rechargeable batteries

? Charge control output operates an

external charge controller such as

the bq2004 Fast Charge IC

? Designed for battery pack integration

- 120μA typical standby current

? Display capacity via single-wire

serial communication port or direct

drive of LEDs

? Measurements compensated for

current and temperature

? Self-discharge compensation using

internal temperature sensor

? User-selectable end-of-discharge

threshold

? Battery voltage, nominal available

charge, temperature, etc.

available over serial port

? 16-pin narrow SOIC

General Description

The bq2014 Gas Gauge IC is intended

for battery-pack or in-system

installation to maintain an accurate

record of available battery charge.

The IC monitors the 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

“l(fā)earned,” in the course of a discharge

cycle from full to empty.

The bq2014 includes a charge control

output that controls an external

Fast Charge IC such as the bq2004.

Nominal Available Charge (NAC)

may be directly indicated using a

five-segment LED display.

The bq2014 supports a simple singleline

bidirectional serial link to an external

processor (with a common

ground). The bq2014 outputs battery

information in response to external

commands over the serial link.

Internal registers include available

charge, temperature, capacity, battery

voltage, 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 bq2014

gas gauge data registers.

The bq2014 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.