Features
➤ Accurate measurement of avail-
able capacity in NiCd or NiMH
batteries
➤ Low-cost battery management so-
lution for pack integration
- As little as
1
2
square inch of
PCB for complete circuit
- Low operating current (120µA
typical)
- Less than 100nA of data
retention current
➤ High-speed (5kb/s) single-wire
communication interface (HDQ
bus) for critical battery
parameters
➤ Communication with an external
charge controller such as the
bq2004
➤ Direct drive of remaining capacity
LEDs
➤ Automatic rate and temperature
compensation of measurements
➤ 16-pin narrow SOIC
General Description
The bq2014H NiCd/NiMH Gas
Gauge IC is intended for battery-
pack or in-system installation to
maintain an accurate record of
available battery capacity. The IC
monitors a voltage drop across a
sense resistor connected in series
between the negative battery termi-
nal and ground to determine
charge and discharge activity of
the battery. Compensations for bat-
tery temperature, self-discharge,
and rate of discharge are applied to
the charge counter to provide avail-
able capacity information across a
wide range of operating conditions.
Battery capacity is automatically re-
calibrated, or “learned,” in the
course of a discharge cycle from full
to empty.
Nominal available capacity may be
directly indicated using a five-
segment LED display. The bq2014H
also supports a simple single-line
bidirectional serial link to an exter-
nal processor (common ground). The
5kb/s HDQ bus interface reduces
communications overhead in the
external microcontroller.
Internal registers include available
capacity and energy, temperature,
voltage and current, and battery
status. The external processor may
also overwrite some of the bq2014H
gas gauge data registers.
The bq2014H can operate from the
batteries in the pack. The REF out-
put and an external transistor allow
a simple, inexpensive voltage regu-
lator to supply power to the circuit
from the cells.
1
Preliminary bq2014H
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
DONE Charge complete
input
1
PN20140H..eps
16-Pin Narrow SOIC
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LCOM
SEG
1
/PROG
1
SEG
2
/PROG
2
SEG
3
/PROG
3
SEG
4
/PROG
4
SEG
5
/PROG
5
DONE
V
SS
V
CC
REF
NC
HDQ
RBI
SB
DISP
SR
V
SS
System ground
SR Sense resistor input
DISP Display control input
SB Battery sense input
RBI Register backup input
HDQ Serial communications
input/output
NC No connect
REF Voltage reference output
V
CC
Supply voltage
Pin Connections
SLUS030–JUNE 1999
Low-Cost NiCd/NiMH Gas Gauge IC
Pin Names