鉃?/div>
Available in 14-pin 300-mil DIP
or 150-mil SOIC
General Description
The bq2903 is a cost-effective charge
controller for rechargeable alkaline
batteries such as Renewal batteries
from Rayovac. The bq2903 combines
sensitive, full-charge detection for
three to four rechargeable alkaline
cells, with a low-battery cut-off for
over-discharge protection.
Designed for integration into a three-
or four-cell system, the bq2903 can
improve the service life of the re-
chargeable alkaline cells by properly
managing the charge and discharge.
The bq2903 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 dam-
aging overcharge.
Charge completion is indicated when
the average charge rate falls below
approximately 6% of the fast charge
rate. Status outputs are provided to
indicate charge in progress, charge
complete, or fault condition.
The bq2903 avoids over-depleting
the battery by using the internal
end-of-discharge control circuitry.
The bq2903 also eliminates the ex-
ternal power switching transistors
needed to separately charge indi-
vidual Renewal cells.
To reduce external component count,
the discharge and charge control
FETs are internal to the bq2903;
however, if the discharge load is
greater than 400mA, a DRV pin is
provided to drive an external N-FET,
reducing the effective discharge path
resistance for the system.
For safety, charging is inhibited if the
voltage of any cell is greater than
3.0V during charge or if the voltage of
any cell is less than 0.4V when not
charging (open-circuit voltage).
Pin Connections
Pin Names
DC
CHG
Charging supply input
Battery status output 1
Battery status output 2
Number of cells input
End of discharge
voltage select input
Battery 1 positive input
BAT
1N
BAT
2N
BAT
3N
V
SS
Battery 1 negative input
Battery 2 negative input
Battery 3 negative input
Battery 4 negative input/
IC ground
System load returns
External FET drive
output
BAT1N
BAT2N
BAT3N
NSEL
VSEL
DONE
CHG
1
2
3
4
5
6
7
14
13
12
11
10
9
8
BAT1P
DC
LRTN
2
VSS
VSS
LRTN
1
DRV
DONE
N
SEL
V
SEL
LRTN
1, 2
DRV
BAT
1P
14-Pin Narrow DIP
or SOIC
PN290301.eps
6/99 C
1