Features

➤

Complete and compact lithium ion gas gauge and

protection solution for three or four series cells

➤

Accurate measurement of available battery

capacity

➤

Provides overvoltage, undervoltage, and

overcurrent protection

➤

Designed for battery pack integration

–

Small size

–

Includes bq2050H and bq2058 ICs

–

On-board charge and discharge control FETs

–

Low operating current for minimal battery drain

➤

High side FET control

➤

Battery capacity available through single-wire

serial port

➤

“L” version includes 5 push-button activated LEDs

to display state-of-charge information

General Description

The bq2168 Power Gauge Module provides a complete and

compact battery management solution for Li-Ion battery

packs. Designed for battery pack integration, the bq2168

combines the bq2050H Power Gauge IC with the bq2058

Supervisor IC on a small printed circuit board. The board

includes all the necessary components to accurately monitor

battery capacity and protect the cells from overvoltage, un-

dervoltage, and overcurrent conditions. The board works

with three or four Li-Ion series cells.

The Power Gauge IC uses the on-board sense resistor to

track charge and discharge activity of the battery pack.

Critical battery information can be accessed through the

serial communications port at HDQ. The supervisor cir-

cuit consists of the bq2058 and two FETs. The bq2058

controls the FETs to protect the batteries during

charge/discharge cycles and short circuit conditions. The

bq2168 provides contacts for the positive and negative

terminals of each battery in the stack. Please refer to

the bq2050H and bq2058 data sheets for the specifics on

the operation of the power gauge and supervisor ICs.

Unitrode configures the bq2168 based on the informa-

tion requested in Table 1. The configuration defines the

number of series cells, the nominal battery pack capac-

ity, the self-discharge rate, the Li-Ion battery type (coke

or graphite anode), and the threshold limits. Figure 1

shows how the module connects to the cells.

The bq2168L includes five LEDs to display remaining capac-

ity in 20% increments of the learned capacity. The LEDs are

activated with the onboard push-button switch.

A module development kit is also available for the

bq2168. The bq2168B-KT or the bq2168LB-KT includes

one configured module and the following:

1)

An EV2200-50H interface board that allows con-

nection to the serial port of any AT-compatible com-

puter.

2)

Menu driven software to display charge/discharge

activity and to allow user interface to the bq2050H

from any standard Windows 3.1x or 95 PC.

Pin Descriptions

POS

Pack positive

B1P

B1N

B2N

B3N

B4N

ITEST

Overcurrent test input

HDQ

Serial communications port

NEG

Pack negative

1

bq2168

5/99 B

Li-Ion Power Gauge™ Module

with Pack Supervisor