BQ2012_15 Datasheet, PDF (3/26 Pages) Texas Instruments – Gas Gauge IC With Slow-Charge Control

Not Recommended For New Designs
bq2012
Functional Description
General Operation
The bq2012 determines battery capacity by monitoring
the amount of charge input to or removed from a re-
chargeable battery. The bq2012 measures discharge and
charge currents, estimates self-discharge, monitors the
battery for low-battery voltage thresholds, and compen-
sates for temperature and charge/discharge rates. The
charge measurement is made by monitoring the voltage
across a small-value series sense resistor between the
negative battery terminal and ground. The available
battery charge is determined by monitoring this voltage
over time and correcting the measurement for the envi-
ronmental and operating conditions.
Figure 1 shows a typical battery pack application of the
bq2012 using the LED display capability as a charge-
state indicator. The bq2012 can be configured to display
capacity in either a relative or an absolute display mode.
The relative display mode uses the last measured dis-
charge capacity of the battery as the battery “full” refer-
ence. The absolute display mode uses the programmed
full count (PFC) as the full reference, forcing each seg-
ment of the display to represent a fixed amount of
charge. A push-button display feature is available for
momentarily enabling the LED display.
The bq2012 monitors the charge and discharge currents
as a voltage across a sense resistor (see RS in Figure 1).
A filter between the negative battery terminal and the
SR pin may be required if the rate of change of the bat-
tery current is too great.
bq2012
Gas Gauge IC
REF
LCOM
SEG1/PROG1
SEG2/PROG2
SEG3/PROG3
SEG4/PROG4
SEG5/PROG5
SEG6/PROG6
CHG
VCC
SB
DISP
SR
VSS
EMPTY
DQ
R1
1M
C1
0.1 F
Q1
ZVNL110A
VCC
RB1
VCC
RB2
RS
Indicates optional.
Directly connect to VCC across 3 or 4 cells (3 to 4.8V nominal,should not
exceed 6.5V) with a resistor and a Zener diode to limit voltage during charge.
Otherwise, R1, C1, and Q1 are needed for regulation of >4 cells.
The value of R1 depends on the number of cells.
Programming resistors (6 max.) and ESD-protection diodes are not shown.
R-C on SR may be required (application-specific), where the R
should not exceed 100k.
Charger
Load
FG201201.eps
Figure 1. Battery Pack Application Diagram—LED Display
3