U2402B
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
1 (17)
Fast Charge Controller for NiCd/NiMH Batteries
Description
The fast-charge battery controller circuit, U2402B, uses
bipolar technology. The IC enables the designer to create
an efficient and economic charge system. The U2402B
incorporates intelligent multiple-gradient battery-
voltage monitoring and mains phase control for power
management. With automatic top-off charging, the
integrated circuit ensures that the charge device stops
regular charging, before the critical stage of overcharging
is achieved. It has two LED driver indications for charge
and temperature status.
Features
D Multiple gradient monitoring
D Temperature window (T
min
/T
max
)
D Exact battery voltage measurement without charge
D Phase control for charge-current regulation
D Top-off and trickle charge function
D Two LED outputs for charge status indication
D Disabling of d
2
V/dt
2
switch-off criteria
during battery formation
D Battery-voltage check
Applications
D Portable power tools
D Laptop/notebook personal computer
D Cellular/cordless phones
D Emergency lighting systems
D Hobby equipment
D Camcorder
Package: DIP18, SO20
Gradient
d
2
V/dt
2
and dV
5 (5)
Sync
R
Phase control
18 (20)
17 (19)
16 (18)
Power supply
V
S
= 8 to 26 V
Trigger output
V
i
Power - on control
V
Ref
6.5 V/10 mA
14 (15)
Oscillator
160 mV
Ref
Temp. control
T
max
Sensor
Battery
detection
V
Ref
= 5 V
Status control
Scan path
V
Batt
Monitor
0.1 to 4 V
Charge break
output
Control unit
13 (14)
12 (13)
11 (12)
3 (3)
10 (11)
6 (6)
7 (8)
8 (9)
9 (10)
4 (4)
1 (1)
15 (17)
2 (2)
94 8585
C
( ) SO 20, Pins 7 and 16 NC
Figure 1. Block diagram
U2402B
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
2 (17)
Pinning
Package: DIP18
18
10
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
Output
GND
LED2
LED1
93 7723 e
V
i
t
p
V
sync
C
R
V
Ref
Osc
S
TM.
V
S
V
Batt
OP
O
OP
I
T
max
Sensor
Package: SO20
18
10
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
Output
GND
LED2
LED1
94 8594
20
19
V
i
OP
O
t
p
NC
V
Batt
S
TM.
Osc
V
Ref
R
C
V
sync
V
S
NC
OP
I
T
max
Sensor
Pin Description
Pin
Symbol
Function
1
Output
Trigger output
2
GND
Ground
3
LED2
Display output "Green"
4
V
i
Phase angle control input voltage
5
OP
O
Operational amplifier output
6
OP
I
Operational amplifier input
7
T
max
Maximum temperature
8
Sensor
Temperature sensor
9
t
p
Charge break output
10
V
Batt
Battery voltage
11
LED1
LED display output "Red"
12
S
TM.
Test mode switch (status control)
13
Osc
Oscillator
14
V
Ref
Reference output voltage
15
V
S
Supply voltage
16
R
Ramp current adjustment
resistance
17
C
Ramp voltage capacitance
18
V
sync.
Mains synchronization input
Pin
Symbol
Function
1
Output
Trigger output
2
GND
Ground
3
LED2
Display output "Green"
4
V
i
Phase angle control input voltage
5
OP
O
Operational amplifier output
6
OP
I
Operational amplifier input
7
NC
Not connected
8
T
max
Maximum temperature
9
Sensor
Temperature sensor
10
t
p
Charge break output
11
V
Batt
Battery voltage
12
LED1
LED display output "Red"
13
S
TM.
Test mode switch (status control)
14
Osc
Oscillator
15
V
Ref
Reference output voltage
16
NC
Not connected
17
V
S
Supply voltage
18
R
Ramp current adjustment
resistance
19
C
Ramp voltage capacitance
20
V
sync.
Mains synchronization input
U2402B
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
3 (17)
Sync
R
C
Phase control
18
17 16
Power supply
V
S
= 8 to 26
V
T
rigger output
V
i
Power on
control
V
Ref
6.5 V/10
mA
14
Oscillator
160 mV
Ref
T
emp. control
T
max
Sensor
Battery
detection
V
Ref
= 5
V
Status
control
Scan path
V
Batt
Monitor
0.1 to 4
V
Char
ge break
output
Contr
ol unit
Gradient
d
2
V/dt
2 & dV
13 12
11
3
10
5
6
7
8
9
4
94 8674
R
3
2.2 k
R
13
100 k
R
4
560 k
C
3
10 nF
C
2
0.22 F
R
0
270 k
C
0
10 nF
Red
D
7
D
8
Green
C
6
0.1 F
10 k
R
2
D
1
10
1
D
4
D
5
D
2
D
3
Th1
Th2
Mains
D
6
R
10
R
11
560
2x
R
9
R
8
1 k
R
7
1 k
BC 308
T
1
R
1
1 k
R
5
C
1
470 F
R
B1
10 k
C
R
1 F
R
6
10 k
C
4
R
T3
24 k
0.1 F
C
8
R
T2
100 k
R
T1
To
V
Ref
(Pin 14)
R
B2
C
7
4.7 F
R
B3
NTC
DC
0.2
Battery
(4 cells)
T
o
Pin 4
From
R
T1
/ R
T2
15
2
1 k
16 k
R
sh
160 mV
12 k
I ch
W
W
W
W
m
W
m
1 F
m
W
W
W
m
W
W
m
W
10 k
m
W
W
W
W
m
W
W
W
W
V
S
V
S
From Pin 15
Figure 2. Block diagram with external circuit (DIP pinning)
U2402B
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
4 (17)
General Description
The integrated circuit, U2402B, is designed for charging
Nickel-Cadmium (NiCd) and Nickel-Metal-Hydride
(NiMH) batteries. Fast charging results in voltage lobes
when fully charged (figure 3). It supplies two identifica-
tions ( i. e., + d
2
V/dt
2
,
and
DV) to end the charge
operation at the proper time.
As compared to the existing charge concepts where the
charge is terminated
* after voltage lobes * according
to
DV and temperature gradient identification, the
U2402B-C takes into consideration the additional
changes in positive charge curves, according to the se-
cond derivative of the voltage with respect to time
(d
2
V/dt
2
). The charge identification is the sure method of
switching off the fast charge before overcharging the bat-
tery. This helps to give the battery a long life by hindering
any marked increase in cell pressure and temperature.
Even in critical charge applications, such as a reduced
charge current or with NiMH batteries where weaker
charge characteristics are present multiple gradient con-
trol results in very efficient switch-off.
An additional temperature control input increases not
only the performances of the charge switching character-
istics but also prevents the general charging of a battery
whose temperature is outside the specified window.
A constant charge current is necessary for continued
charge-voltage characteristic. This constant current regu-
lation is achieved with the help of internal amplifier phase
control and a simple shunt-current control technique.
All functions relating to battery management can be
achieved with dc-supply charge systems. A dc-dc-con-
verter or linear regulator should take over the function of
power supply. For further information please refer to the
applications.
shorted batteries ignored
check
Battery insertion
Battery
monitoring
voltage
5 V
formation
Battery
DV
t
) d
2
V
dt
2
t
2
v 20 min
V
10
DV, ) d
2
V
dt
2
, active
t
1
= 5 min
Fast charge rate I
O
Top off
charge rate
1/4 I
O
Trickle
charge rate
1/256 I
O
Gradient recognition
95 10172
DV
Figure 3. Charge function diagram, f
osc
= 800 Hz
U2402B
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
5 (17)
Flow Chart Explanation, f
osc
= 800 Hz
(Figures 2, 3 and 4)
Battery pack insertion disables the voltage lock at battery
detection input Pin 10. All functions in the integrated
circuit are reset. For further description, DIP-pinning is
taken into consideration.
Battery Insertion and dV Monitoring
The charging procedure will be carried out if battery
insertion is recognised. If the polarity of the inserted
battery is not according to the specification, the fast
charge rate will stop immediately. After the polarity test,
if positive, the defined fast charge rate, I
O
, begins for the
first 5 minutes according to dV monitoring. After
5 minutes of charging, the first identification control is
executed.
If the inserted battery has a signal across its terminal of
less than 0.1 V, then the charging procedure is interrupted.
This means that the battery is defective i.e., it is not a
rechargeable battery "shorted batteries ignored".
Voltage and temperature measurements across the battery
are carried out during charge break interval (see figure 6),
i.e., currentless or idle measurements.
If the inserted battery is fully charged, the dV control
will signal a charge stop after six measurements
(approximately 110 seconds). All the above mentioned
functions are recognised during the first 5 minutes
according to dV method. During this time, +d
2
V/dt
2
remains inactive. In this way the battery is protected from
unnecessary damage.
d
2
V/dt
2
-Gradient
If there is no charge stop within the first 5 minutes after
battery insertion, then d
2
V/dt
2
monitoring will be active.
In this actual charge stage, all stop-charge criteria are
active.
When close to the battery's capacity limit, the battery
voltage curve will typically rise. As long as the +d
2
V/dt
2
stop-charging criteria are met, the device will stop the fast
charge activities.
Top-Off Charge Stage
By charge disconnection through the + d
2
V/dt
2
mode, the
device switches automatically to a defined protective
top-off charge with a pulse rate of 1/4 I
O
(pulse time,
t
p
= 5.12 s, period, T = 20.48 s).
The top-off charge time is specified for a time of
20 minutes @ 800 Hz.
Trickle Charge Stage
When top-off charge is terminated, the device switches
automatically to trickle charge with 1/256 I
O
(t
p
= 5.12 s,
period = 1310.72 s). The trickle continues until the
battery pack is removed.
Basic Description
Power Supply, Figure 2
The charge controller allows the direct power supply of
8 to 26 V at Pin 15. Internal regulation limits higher input
voltages. Series resistance, R
1
, regulates the supply
current, I
S
, to a maximum value of 25 mA. Series
resistance is recommended to suppress the noise signal,
even below 26 V limitation. It is calculated as follows:
R
1min
w
V
max
26 V
25 mA
R
1max
v
V
min
8 V
I
tot
where
I
tot
= I
S
+ I
RB1
+ I
1
V
max,
V
min
= Rectified voltage
I
S
= Current consumption (IC) without load
I
RB1
= Current through resistance, R
B1
I
1
= Trigger current at Pin 1
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