BQ2002C_11 Datasheet, PDF (2/17 Pages) Texas Instruments – NiCd/NiMH Fast-Charge Management IC

bq2002C
Pin Descriptions
TM
LED
BAT
VSS
TS
VCC
INH
Timer mode input
A three-level input that controls the settings
for the fast charge safety timer, voltage ter-
mination mode, pulse-trickle, and voltage
hold-off time.
Charging output status
Open-drain output that indicates the charging
status.
Battery input voltage
The battery voltage sense input. The input to
this pin is created by a high-impedance re-
sistor divider network connected between
the positive and negative terminals of the
battery.
System ground
Temperature sense input
Input for an external battery temperature
monitoring thermistor.
Supply voltage input
5.0V ± 20% power input.
Charge inhibit input
When high, INH suspends the fast charge in
progress. When returned low, the IC re-
sumes operation at the point where initially
suspended.
CC
Charge control output
An open-drain output used to control the
charging current to the battery. CC switch-
ing to high impedance (Z) enables charging
current to flow, and low to inhibit charging
current. CC is modulated to provide pulse
trickle.
Functional Description
Figure 2 shows a state diagram and Figure 3 shows a
block diagram of the bq2002C.
Battery Voltage and Temperature
Measurements
Battery voltage and temperature are monitored for
maximum allowable values. The voltage presented on
the battery sense input, BAT, should represent a
single-cell potential for the battery under charge. A
resistor-divider ratio of
RB1 _{= N - 1}
RB2
is recommended to maintain the battery voltage within
the valid range, where N is the number of cells, RB1 is
the resistor connected to the positive battery terminal,
and RB2 is the resistor connected to the negative
battery terminal. See Figure 1.
Note: This resistor-divider network input impedance to
end-to-end should be at least 200kΩ and less than 1 MΩ.
A ground-referenced negative temperature coefficient
thermistor placed near the battery may be used as a low-
cost temperature-to-voltage transducer. The temperature
sense voltage input at TS is developed using a resistor-
thermistor network between VCC and VSS. See Figure 1.
RB1
BAT
bq2002C
RB2
VSS
VCC
RT
R3
VCC
TM
TS
R4
bq2002C
VSS
PACK +
N
T
C
BAT pin connection
Mid-level
setting for TM
Thermistor connection
NTC = negative temperature coefficient thermistor.
Fg2002/C.eps
Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration
2