
1
Features
Conservative and repeatable
measurement of available charge
in rechargeable batteries
Charge control output
Designed for battery pack inte-
gration
-
120
μ
A typical standby current
(self-discharge estimation mode)
-
Small size enables imple-
mentations in as little as
12
square inch of PCB
Integrate within a system or as a
stand-alone device
-
Display capacity via single-
wire serial communication
port or direct drive of LEDs
Measurements compensated for
current and temperature
Self-discharge compensation us-
ing internal temperature sensor
16-pin narrow SOIC
General Description
The bq2012 Gas Gauge IC is in-
tended for battery-pack or in-system
installation to maintain an accurate
record of available battery charge.
The IC monitors a voltage drop
across a sense resistor connected in
series between the negative battery
terminal and ground to determine
charge and discharge activity of the
battery.
Self-discharge of NiMH and NiCd
batteries is estimated based on an
internal timer and temperature sen-
sor. Compensations for battery tem-
perature and rate of charge or dis-
charge are applied to the charge,
discharge, and self-discharge calcu-
lations to provide available charge
information across a wide range of
operating conditions. Battery capac-
ity is automatically recalibrated, or
“learned,” in the course of a dis-
charge cycle from full to empty.
The bq2012 includes a charge con-
trol output that, when used with
other full-charge safety termination
methods, can provide a cost-effective
means of controlling charge based
on the battery's charge state.
Nominal available charge may be di-
rectly indicated using a five- or six-
segment LED display.
ments are used to graphically indi-
cate nominal available charge.
These seg-
The bq2012 supports a simple
single-line bidirectional serial link to
an external processor (common
ground). The bq2012 outputs battery
information in response to external
commands over the serial link.
Internal registers include available
charge, temperature, capacity, battery
ID, battery status, and programming
pin settings. To support subassembly
testing, the outputs may also be con-
trolled. The external processor may
also overwrite some of the bq2012 gas
gauge data registers.
The bq2012 may operate directly
from three or four cells.
REF output and an external transis-
tor, a simple, inexpensive regulator
can be built to provide V
CC
across a
greater number of cells.
With the
LCOM
LED common output
SEG
1
/PROG
1
LED segment 1/
program 1 input
SEG
2
/PROG
2
LED segment 2/
program 2 input
SEG
3
/PROG
3
LED segment 3/
program 3 input
SEG
4
/PROG
4
LED segment 4/
program 4 input
SEG
5
/PROG
5
LED segment 5/
program 5 input
SEG
6
/PROG
6
LED segment 6/
program 6 input
1
PN201201.eps
16-Pin Narrow SOIC
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LCOM
SEG1/PROG1
SEG2/PROG2
SEG3/PROG3
SEG4/PROG4
SEG5/PROG5
SEG6/PROG6
VSS
VCC
REF
CHG
DQ
EMPTY
SB
DISP
SR
REF
Voltage reference output
CHG
Charge control output
DQ
Serial communications
input/output
EMPTY
Empty battery indicator
output
SB
Battery sense input
DISP
Display control input
SR
Sense resistor input
V
CC
3.0–6.5V
V
SS
System ground
Pin Connections
Pin Names
bq2012
Gas Gauge IC With
Slow-Charge Control
9/96 B