TEXAS INSTRUMENTS bq2002C Technical data
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bq2002C
NiCd/NiMH Fast-Charge Management IC
Features
Fast charge of nickel cadmium
➤
or nickel-metal hydride batter
ies
Direct LED output displays
➤
charge status
Fast-charge termination by -∆V,
➤
maximum voltage, maximum
temperature, and maximum
time
Internal band-gap voltage ref
➤
erence
Selectable pulse-trickle charge
➤
rates
➤ Low-power mode
➤ 8-pin 300-mil DIP or 150-mil
SOIC
Pin Connections
TM
LED
BAT
V
SS
1
2
3
4
8
CC
7
INH
V
6
CC
TS
5
General Description
The bq2002C F ast-Charge IC is a lowcost CMOS battery-charge controller
providing reliable charge termination
for both NiCd and NiMH battery appli
cations. Controlling a current-limited
or constant-current supply allows the
bq2002C to be the basis for a costeffective stand-alone or system-inte
grated charger. The bq2002C inte
grates fast charge with pulsed-trickle
control in a single IC for charging one
or more NiCd or NiMH battery cells.
Fast charge is initiated on application
of the charging supply or battery
replacement. For safety, fast charge is
inhibited if the battery temperature
and voltage are outside configured
limits.
Pin Names
TM Timer mode select input
LED
BAT Battery voltage input
V
SS
Charging status output
System ground
Fast charge is terminated by any of
the following:
Peak voltage detection (PVD)
n
Negative delta voltage (-∆V)
n
Maximum voltage
n
Maximum temperature
n
-
Maximum time
n
-
After fast charge, the bq2002C pulsetrickles the battery per the preconfigured limits. Fast charge may be
inhibited using the INH pin. The
bq2002C may also be placed in lowstandby-power mode to reduce
system power consumption.
TS Temperature sense input
V
CC
Supply voltage input
INH Charge inhibit input
CC Charge control output
9/97 B
8-Pin DIP or
Narrow SOIC
PN-200201.eps
1
bq2002C
Pin Descriptions
TM
LED
BAT
V
SS
TS
V
CC
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
Temperaturesenseinput
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 Voltageand 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-dividerratioof
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 lowcost temperature-to-voltage transducer. The temperature
sense voltage input at TS is developed using a resistorthermistor network between V
and VSS. See Figure 1.
CC
-
V
CC
RB1
BAT
bq2002C
BAT pin connection Thermistor connection
RB2
V
SS
NTC = negative temperature coefficient thermistor.
R3
R4
Mid-level
setting for TM
V
CC
TM
bq2002C
T
V
SS
PACK +
RT
S
N
T
C
Fg2002/C.eps
Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration
2
bq2002C
OSC
V
CC
Chip on
4.0V
V
TS
V
BAT
0.84V < V
BAT
/2
> V
CC
Fast
LED =
Low
V
BAT
VTS < VCC/2 or
PVD or - V or
Maximum Time Out
Clock
Phase
Generator
Battery Voltage
too High?
< 2V
Battery Voltage
too Low?
Battery
Temperature?
> 2V or
V
V
V
BAT
BAT
TS
V
> V
2V
>
BAT
< 0.84V
V
BAT
< V
V
CC
TS
> 0.84V and
< 2V and
/2
CC
/2
Figure 2. State Diagram
Trickle
LED =
Flash
Trickle
LED = Z
Charge
Pending
V
BAT
V
> 2V
BAT
2V
20
D
S
s
p
.e
C
02
TM
INH
Charge-Control
State Machine
Power-On
Reset
Timing
Control
Sample
History
PVD, - V
ALU
HTF
Check
CC
LED
Figure 3. Block Diagram
3
TCO
Check
TS
Power
Down
Voltage
Reference
A to D
Converter
LBAT
Check
MCV
Check
V
CC
V
SS
Bd2002CEG.eps
BAT
bq2002C
Fast ChargingVCC = 0 Fast Charging
CC Output
Charge initiated by application of power
Charge initiated by battery replacement
LED
Figure 4. Charge Cycle Phases
Starting ACharge Cycle
Either of two events starts a charge cycle (see Figure 4):
1.Applicationofpowerto V
2. Voltage at the BAT pin falling through the maximum
cell voltage V
MCV
where
V
If the battery is within the configured temperature and
voltage limits, the IC begins fast charge. The valid
battery voltage range is V
V
LBAT
The valid temperature range is V
V
HTF
If V
BAT
≤ V
LBAT
or VTS≤ V
or
CC
= 2V ±5%.
MCV
LBAT<VBAT<VMCV,
= 0.175 ∗ VCC±20%
TS>VHTF
= 0.6 ∗ VCC±5%.
, the IC enters the charge-
HTF
where
where
Pulse-Trickle
1s
See
Table 1
TD2002C1.eps
pending state. In this state pulse trickle charge is
applied to the battery and the LED flashes until the
voltage and temperature come into the allowed fast
charge range or V
≥ V
, the IC enters the Charge Complete/Battery
MCV
rises above V
BAT
. Anytime V
MCV
BAT
Absent state. In this state the LED is off and trickle
charge is applied to the battery until the next new
charge cycle begins.
Fast charge continues until termination by one or more of
the five possible termination conditions:
n
Peak voltage detection (PVD)
n
Negative delta voltage (-∆V)
n
Maximum voltage
n
Maximum temperature
n
Maximum time
Table 1. Fast-Charge Safety Time/Hold-Off Table
Typical
Corresponding
Fast-Charge
Rate TM Termination
Fast-
Charge
Time Limits
(minutes)
Typical PVD
and -∆V
Hold-Off
Time (seconds)
Pulse-
Trickle
Rate
C/2 Mid PVD 160 300 C/32 73 18.7
1C Low PVD 80 150 C/32 37 18.7
2C High -∆V 40 75 C/32 18 9.4
Notes: Typical conditions = 25°C, VCC= 5.0V
Mid = 0.5*V
CC
±0.5V
Tolerance on all timing is ±12%.
4
Pulse-
Trickle
Pulse Width
(ms)
Maximum
Synchronized
Sampling
Period
(seconds)
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