Datasheet

Functional Description
General Operation
The bq2050 determines battery capacity by monitor
-
ing the amount of current input to or removed from a
rechargeable battery. The bq2050 measures dis
-
charge and charge currents, measures battery volt
-
age, estimates self-discharge, monitors the battery
for low battery voltage thresholds, and compensates
for temperature and charge/discharge rates. The cur
-
rent measurement is made by monitoring the voltage
across a small-value series sense resistor between the
negative battery terminal and ground. The estimate of
scaled available energy is made using the remaining
average battery voltage during the discharge cycle
and the remaining nominal available charge. The
scaled available energy measurement is corrected for
the environmental and operating conditions.
Figure 1 shows a typical battery pack application of the
bq2050 using the LED display capability as a charge-
state indicator. The bq2050 is configured to display ca
-
pacity 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 bq2050 monitors the charge and discharge currents
as a voltage across a sense resistor (see R
S
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.
3
bq2050
FG205001.eps
PROG
6
SEG
5
/PROG
5
SEG
4
/PROG
4
SEG
3
/PROG
3
SEG
2
/PROG
2
SEG
1
/PROG
1
SR
DISP
SB
V
CC
REF
bq2050
Power Gauge IC
LCOM
V
SS
RBI
DQ
V
CC
C1
0.1 F
Q1
ZVNL110A
R
1
R
S
RB
1
RB
2
Load
Charger
Indicates optional.
Directly connect to V
CC
across 1 cell (V
BAT
> 3V).
Otherwise, R1, C1, and Q1 are needed for regulation of > 1 cell.
Programming resistors (6 max.) and ESD-protection diodes are not shown.
R-C on SR may be required, application-specific.
A series Zener may be used to limit discharge current at low voltages
in desi
g
ns usin
g
3 or more cells.
V
CC
C2
1M
PSTAT
Figure 1. Battery Pack Application Diagram—LED Display