1
Features
➤ Safely charges two rechargeable
alkaline batteries such as Re-
newal
®
from Rayovac
®
➤ Terminates pulsed charge with
maximum voltage limit
➤ Contains LED charge status out-
put
➤ Features a pin-selectable
low-battery cut-off
➤ Pre-charge qualification indicates
fault condition
➤ Available in 8-pin 300-mil DIP or
150-mil SOIC
General Description
The bq2902 is a low-cost charger for
rechargeable alkaline batteries such
as Renewal
®
batteries from Rayovac
®
.
The bq2902 combines sensitive, full-
charge detection for two recharge-
able alkaline cells, with a low-battery
cut-off for overdischarge protection.
Designed for system integration
into a two-cell system, the bq2902
can improve the service life of the
rechargeable alkaline cells by prop-
erly managing the charge and dis-
charge. The bq2902 requires a
voltage limited current source to
generate the proper charge pulses
for the Renewal
®
cell. Each cell is
individually monitored to ensure
full charge without a damaging
overcharge.
Charge completion is indicated
when the average charge rate falls
below approximately 3% of the fast
charge rate. A status output is pro-
vided to indicate charge in progress,
charge complete, or fault indication.
The bq2902 avoids over-depleting
the battery by using the internal
end-of-discharge control circuit.
The bq2902 also eliminates the
external power switching transis-
tors needed to separately charge
individual Renewal cells.
For safety, charging is inhibited if
the per-cell voltage is greater than
3.0V during charge (closed-circuit
voltage), or if the cell voltage is less
than 0.4V (open-circuit voltage).
Rechargeable Alkaline Charge/Discharge
Controller IC
bq2902
5/99 C
1
PN290201.eps
8-Pin Narrow DIP
or SOIC
2
3
4
8
7
6
5
V
SEL
BAT
1N
BAT
1P
DC
CHG
V
SS
V
SS
LRTN
DC Charging supply input
CHG Battery status output
BAT1P Battery 1 positive input
BAT1N Battery 1 negative input
V
SS Battery 2 negative input
IC ground
LRTN System load return
VSEL End-of-discharge voltage
select input
Pin NamesPin Connections