Functional Description

General Operation

The bq2011 determines battery capacity by monitoring

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

chargeable battery. The bq2011 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 is made by monitoring the voltage

across a small-value series sense resistor between the

negative battery terminal and ground.

The available

battery charge is determined by monitoring this voltage

over time and correcting the measurement for the envi-

ronmental and operating conditions.

Figure 1 shows a typical battery pack application of the

bq2011 using the LED display with absolute mode as a

charge-state indicator. The bq2011 can be configured to

display capacity in either a relative or an absolute dis-

play mode.

The relative display mode uses the last

measured discharge capacity of the battery as the bat-

tery “full” reference. The absolute display mode uses the

programmed full count (PFC) as the full reference, forc-

ing each segment of the display to represent a fixed

amount of charge.

A push-button display feature is

available for momentarily enabling the LED display.

The bq2011 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

bq2011

FG201101.eps

PFC

SEG5

SEG4

SEG3

SEG2

SEG1

VSS

DISP

SB

VCC

REF

bq2011

Gas Gauge IC

MODE

SR

RBI

DQ

VCC

C1

0.1 F

Q1

ZVNL110A

R1

RS

RB1

RB2

Load

Charger

Indicates optional.

Directly connect to VCC across 4 cells (4.8V nominal and should not

exceed 6.5V) with a resistor and a Zener diode to limit voltage during charge.

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

Programming resistors and ESD-protection diodes are not shown.

R-C on SR may be required, (application-specific), where the maximum

R should not exceed 20K.

Figure 1. Battery Pack Application Diagram—LED Display,

Absolute Mode