bq2011

Gas Gauge IC for

High Discharge Rates

Features

➤

Conservative and repeatable

measurement of available charge

in rechargeable batteries

➤

Designed for portable equipment

such as power tools with high dis-

charge rates

➤

Designed for battery pack inte-

gration

Nominal available charge may be di-

rectly indicated using a five-seg-

ment LED display. These segments

are used to indicate graphically the

nominal available charge.

The bq2011 supports a simple single-

line bidirectional serial link to an exter-

nal processor (common ground). The

bq2011 outputs battery information in

response to external commands over the

serial link. To support subassembly

testing, the outputs may also be con-

trolled by command. The external proc-

essor may also overwrite some of the

bq2011 gas gauge data registers.

The bq2011 may operate directly

from four cells. With the REF output

and an external transistor, a simple,

inexpensive regulator can be built to

provide V

CC

from a greater number

of cells.

Internal registers include available

charge, temperature, capacity, battery

ID, and battery status.

General Description

The bq2011 Gas Gauge IC is intended

for battery-pack installation to main-

tain an accurate record of available

battery charge. The IC monitors a

voltage drop across a sense resistor

connected in series between the nega-

tive battery terminal and ground to

determine charge and discharge ac-

tivity of the battery. The bq2011 is

designed for systems such as power

tools with very high discharge rates.

Battery self-discharge is estimated

based on an internal timer and tem-

perature sensor. Compensations for

battery temperature and rate of

charge or discharge are applied to

the charge, discharge, and

selfdischarge calculations to provide

available charge information across

a wide range of operating conditions.

Initial battery capacity is set using

the PFC and MODE pins. Actual

battery capacity is automatically

“learned” in the course of a dis-

charge cycle from full to empty and

may be displayed depending on the

display mode.

-

-

120µA typical standby current

(self-discharge estimation mode)

Small size enables imple-

mentations in as little as

1 2

square inch of PCB

➤

Direct drive of LEDs for capacity

display

➤

Self-discharge compensation us-

ing internal temperature sensor

➤

Simple single-wire serial commu-

nications port for subassembly

testing

➤

16-pin narrow SOIC

Pin Connections

MODE

SEG1

SEG2

SEG3

SEG4

SEG5

PFC

VSS

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

VCC

REF

Pin Names

MODE

SEG

1

SEG

2

NC

DQ

RBI

SB

DISP

SR

Display mode output

LED segment 1

LED segment 2

NC

DQ

RBI

No connect

Serial communications

input/output

Register backup input

Battery sense input

Display control input

Sense resistor input

3.0–6.5V

Negative battery terminal

SEG

3

SEG

4

SEG

5

PFC

REF

LED segment 3

SB

LED segment 4

DISP

LED segment 5

SR

Programmed full count

selection input

Voltage reference output

V

CC

V

SS

16-Pin Narrow SOIC

PN201101.eps

2/96 E

1