BQ2014H Datasheet, PDF (3/22 Pages) Texas Instruments – Low-Cost NiCd/NiMH Gas Gauge IC

Preliminary bq2014H
Functional Description
General Operation
The bq2014H determines battery capacity by moni-
toring the amount of current input to or removed
from a rechargeable battery. The bq2014H mea-
sures discharge and charge currents, measures bat-
tery voltage, estimates self-discharge, monitors the
battery for low battery-voltage thresholds, and com-
pensates for temperature and charge/discharge rate.
Current measurement is made by monitoring the
voltage across a small-value series sense resistor be-
tween the negative battery terminal and ground.
The bq2014H compensates the nominal available
capacity register for discharge rate and tempera-
ture and reports the compensated available
capacity. The bq2014H uses the compensated available
capacity to drive the LED display. In addition, the
bq2014H estimates the available energy using the aver-
age battery voltage during the discharge cycle and re-
maining compensated available capacity.
Figure 1 shows a typical battery pack application of the
bq2014H using the LED display capability as a charge-
state indicator. The bq2014H is configured to display
capacity in relative display mode. The relative display
mode uses the last measured discharge capacity of the
battery as the battery “full” reference. A push-button
display feature is available for momentarily enabling
the LED display.
The bq2014H monitors the charge and discharge cur-
rents as a voltage across a sense resistor. (See R_S in Fig-
ure 1.) A filter between the negative battery terminal
and the SR pin is required.
R1
bq2014H
Gas-Gauge IC
REF
LCOM
SEG1/PROG1
SEG2/PROG2
SEG3/PROG3
SEG4/PROG4
SEG5/PROG5
DONE
VCC
SB
DISP
SR
VSS
RBI
HDQ
C1
VCC
100K
0.1µF
Q1
ZVNL110A
VCC
RB1
C2
RB2
RS
1M
See note 4
Notes:
1.
Indicates optional.
2. Programming resistors (5 max.) and ESD-protection diodes are not shown.
3. RC on SR is required.
4. A series diode is required on RBI if the bottom series cell is used as the backup source.
If the cell is used, the backup capacitor is not required, and the anode is connected to the
positive terminal of the cell.
Charger
Load
F2014HBP.eps
Figure 1. Battery Pack Application Diagram—LED Display
3