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 BAT1P/Battery 1 positive input
B1N BAT1N/Battery 1 negative input
B2N BAT2N/Battery 2 negative input
B3N BAT3N/Battery 3 negative input
B4N BAT4N/Battery 4 negative input
ITEST Overcurrent test input
HDQ Serial communications port
NEG Pack negative
1
bq2168
5/99 B
Li-Ion Power Gauge™ Module
with Pack Supervisor