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
- 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
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.
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.
1
Gas Gauge IC for
High Discharge Rates
2/96 E
Pin Connections Pin Names
1
PN201101.eps
16-Pin Narrow SOIC
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
REF
NC
DQ
RBI
SB
DISP
SR
MODE
SEG
1
SEG
2
SEG
3
SEG
4
SEG
5
PFC
V
SS
MODE Display mode output
SEG1 LED segment 1
SEG2 LED segment 2
SEG3 LED segment 3
SEG4 LED segment 4
SEG5 LED segment 5
PFC Programmed full count
selection input
REF Voltage reference output
NC No connect
DQ Serial communications
input/output
RBI Register backup input
SB Battery sense input
DISP Display control input
SR Sense resistor input
VCC 3.0–6.5V
VSS Negative battery terminal
bq2011