1
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 implementations 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 bq2011K Gas Gauge IC is in
tended for battery-pack installation to
maintain an accurate record of a bat
tery’s available charge. The IC moni
tors a voltage drop across a sense re
sistor connected in series between the
negative battery terminal and ground
to determine charge and discharge ac
tivity of the battery. The bq2011K 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 PROG
1-4
and SPFC pins. Actual
battery capacity is automatically
“learned” in the course of a discharge 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 graphically indicate
nominal available charge.
The bq2011K supports a simple
single-line bidirectional serial link to
an external processor (common
ground). The bq2011K outputs bat
tery information in response to exter
nal commands over the serial link. To
support subassembly testing, the
outputs may also be controlled by
command. The external processor
may also overwrite some of the
bq2011K gas gauge data registers.
The bq2011K 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.
LCOM LED common output
SEG
1
/PROG1LED segment 1/ Program
1 input
SEG
2
/PROG2LED segment 2 / Program
2 input
SEG
3
/PROG3LED segment 3/ Program
3 input
SEG
4
/PROG4LED segment 4/ Program
4 input
SEG
5
LED segment 5
SPFC 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
V
CC
3.0–6.5V
V
SS
Negative battery terminal
Gas Gauge IC for
High Discharge Rates
bq2011K
10/97 B
Pin Connections Pin Names
1
PN2011JK.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
LCOM
SEG1/PROG
1
SEG2/PROG
2
SEG3/PROG
3
SEG4/PROG
4
SEG
5
SPFC
V
SS