Functional Description

General Operation

The bq2010 determines battery capacity by monitoring

the amount of charge input to or removed from a re-

chargeable battery. The bq2010 measures discharge and

charge currents, estimates self-discharge, monitors the

battery for low-battery voltage thresholds, and compen-

sates for temperature and charge/discharge rates.

The

charge measurement derives from monitoring the voltage

across a small-value series sense resistor between the

negative battery terminal and ground. The available bat-

tery charge is determined by monitoring this voltage over

time and correcting the measurement for the environ-

mental and operating conditions.

Figure 1 shows a typical battery pack application of the

bq2010 using the LED display capability as a charge-

state indicator. The bq2010 can be configured to display

capacity in either a relative or an absolute display mode.

The relative display mode uses the last measured dis-

charge capacity of the battery as the battery “full” refer-

ence. The absolute display mode uses the programmed

full count (PFC) as the full reference, forcing each seg-

ment of the display to represent a fixed amount of

charge. A push-button display feature is available for

momentarily enabling the LED display.

The bq2010 monitors the charge and discharge currents

A filter between the negative battery terminal and the

SR pin may be required if the rate of change of the bat-

tery current is too great.

3

bq2010

FG201001.eps

SEG6/PROG6

SEG5/PROG5

SEG4/PROG4

SEG3/PROG3

SEG2/PROG2

SEG1/PROG1

SR

DISP

SB

VCC

REF

bq2010

Gas Gauge IC

LCOM

VSS

EMPTY

DQ

VCC

C1

0.1 F

µ

Q1

ZVNL110A

R1

RS

RB1

RB2

Load

Charger

Indicates optional.

Directly connect to VCC across 3 or 4 cells (3 to 5.6V nominal)

with a resistor and a Zener diode to limit voltage during charge.

Otherwise, R1, C1, and Q1 are needed for regulation of >4 cells.

The value of R1 depends on the number of cells.

Programming resistors (6 max.) and ESD-protection diodes are not shown.

R-C on SR may be required, application-specific.

VCC

Figure 1. Battery Pack Application Diagram—LED Display