Rev. 4776A–INDCO–11/03
Features
•Constant Charge Current
•3 h - 24 h Charge Time Programmable
•Low-cost DC Regulator
•Overtemperature Protection
•Charge-mode Indication
•Operation Starts at the Moment of Battery Insertion
•Fast Charge-time Test Mode
Applications
•Cordless Telephones
•Low-cost Battery-charge Timers
•Entertainment Equipment
Description
The U2403B is a monolithic integrated bipolar circuit which can be used in applica-
tions where time-controlled, constant current charge is required. The selection of the
charge current versus timing is carried out by using the external circuit at pins 2, 3 and
4. For high current requirements, an external transistor is recommended in series with
the battery. To protect the IC against high power loss (typically > 140°C), the oscillator
will be shut down when the reference voltage is switched off (0 V). The latter also
takes place when there is a saturation caused by collector voltage at pin 1. When the
overtemperature has disappeared and the collector voltage at pin 1 has exceeded the
supply voltage (V1 > VS), charge time operation continues (see flow chart in Figure 4
on page 6).
Charge Timer IC
U2403B
2U2403B
4776A–INDCO–11/03
Figure 1. Block Diagram with External Circuit
Power supply
VS= 3.5 to 12 V
Charge mode
indicator
Test
mode
RC
oscillator
ϑmax
140°C
í
86
5
4
32
1
7
Power
supply
AC/DC
Battery
inserted LED GND
Shunt Sense Osc
+
-
Timer and control logic
VRef = 1.5 V/0.1 V/0 V
R5
LED2
Charge Ready
LED1
R1C1
VS
V1
R3
R4C4
VRef
STM
3
U2403B
4776A–INDCO–11/03
Pin Configuration
Figure 2. Pinning DIP8/SO8
Pin 1, Collector Voltage
V1
Pin 1 is an open-collector output. When V1 £ 3 V, the charge cycle will be switched off
until it has reached a value higher than the supply voltage, as shown in Figure 6 on page
10.
Pin 2, Shunt Emitter The constant current source is supplied by the internal operational amplifier. The volt-
age across R3 is determined via the internal reference source.
Ich = V3/R3(V3 = Vsense)
Pin 3, Amplifier Sense
Input (Inverted)
The voltage-regulated current source has a closed loop at pin 2, pin 3, and resistor R3.
Pin 4, Oscillator Input R4,
C4
The selection of the current charge versus timing is carried out by using the external cir-
cuit at pins 2, 3, and 4. Typical values are given in Table 1 on page 5.
1
2
3
4
8
7
6
5
V1
V2
SENSE
OSC
LED
U2403B
VS
STM
GND
Pin Description
Pin Symbol Function
1 V1 Collector terminal
2 V2 Shunt emitter terminal
3 V3 Amplifier sense input
4 OSC Oscillator input
5 STM Test-mode switch
6 VS Supply voltage
7 GND Reference point, GND
8 LED Charge-mode indicator
4U2403B
4776A–INDCO–11/03
Pin 5, Test-mode Switch
for Charging Time
The charging time, tch, is given by the following equation:
where:
fosc = oscillator frequency (see Figure 3)
n = frequency divider
= 26, if STM open
= 17, if STM = GND
= 8, if STM = VS
The first eight divider stages can be tested directly. 256 input tact signals at pin 4 create
one tact signal at pin 5.
Figure 3. Quick Test Timer 1/3
Example The charge time is assumed to be 6 h.
The values of R4 and C4 can be selected from Table 1 on page 5.
For example: R4 = 470 kW
C4 = 680 pF
There is a frequency of approximately 3100 Hz at pin 4. It is possible to test the charge
time of 6 h by running through the charge cycle for a very short time. By connecting pin
5 with GND, the test time is 42 s. By connecting pin 5 with pin 1 (V1), the test time is
reduced to about 82.4 ms. R5 is connected in parallel to the LED2 and provides a pro-
tective bypass function for the LED (see Figure 1 on page 2).
Pin 6, Supply Voltage, VSVS » 3.1 V Power-on reset release (turn-on)
VS » 2.9 V Under-voltage reset
VS » 13 V Supply voltage limitation
Pin 7, Ground
tch 1
fosc
---------2n
´=
12 3 256
Oscillator Pulse
Test-mode
Pin 4
Pin 5
5
U2403B
4776A–INDCO–11/03
Pin 8, Charge Mode
Indicator
An open-collector output supplies constant current to LED1 after the active charge
phase has been terminated. Jmax controls the function temperature for the final stage
range. This is when the temperature is above 140°C and the charge function is therefore
switched off.
Trickle Charge The trickle charge starts after the charge has been terminated. In this case, the internal
reference voltage is reduced from 1.5 V to approximately 0.1 V. This means the charge
current is decreased by the factor:
K = 1.5 V/0.1 V = 15
Trickle current = Ich/15 + I6 (supply current) + I8
It is possible to reduce the trickle charge with resistor R6, as shown in Figure 7 on page
11 and Figure 8 on page 13.
Charge Characteristics
Table 1. Charge Time
Test Time/Test-mode Switch STM Oscillator Components Frequency
Open VSGND R4 (kΩ)C
4 (pF) fosc (Hz)
3 h 41.2 ms 21 s
510
430
300
270
330
470
6213
4 h 54.9 ms 28 s
620
430
300
330
470
680
4660
5 h 68.6 ms 35 s
510
390
300
470
680
1000
3728
6 h 82.4 ms 42 s
620
470
360
470
680
1000
3105
7 h 96.1 ms 49 s
560
430
220
680
1000
2200
2663
8 h 109.8 ms 56 s
620
470
200
680
1000
2200
2330
9 h 123.6 ms 1 min 3 s
750
510
240
680
1000
2200
2071
10 h 137.3 ms 1 min 10 s
620
270
130
820
2200
4700
1864
12 h 164.8 ms 1 min 24 s 390
150
2200
4700 1553
16 h 219.7 ms 1 min 56 s 470
200
2200
4700 1165
6U2403B
4776A–INDCO–11/03
Figure 4. Flow Chart
Battery
inserted
LED2 "ON"
Start
Test Open
Divider
GND
Turn on VS > 3.5 V
V3 = 1.5 V
VS
226
Timer start
Tj > T
no
V1 < 3.0 V
yes
yes
V3 ≈ 0 V
Interrupt charging
Interrupt
V1 > VS
no
no
yes
Continuous charging
Continuous timing
End of
timing
Trickle charge mode
Battery
removed
Undervoltage reset
no
no
yes
no
yes
no
yes
Tj < Tmax
V3 = 0 V
V3 = 100 mV
mode
217 28
LED2 "OFF"
LED2 "ON"
LED2 "OFF"
LED1 "ON"
7
U2403B
4776A–INDCO–11/03
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Reference point pin 7 (GND), unless otherwise specified.
Parameters Pin Symbol Value Unit
Supply current
t £ 100 µs 6IS
is
20
100
mA
mA
Currents
1
2
3
4
5
8
I1
-I2
I3
I4
I5
I8
300
310
1
15
-75 to +120
8
mA
mA
µA
mA
µA
mA
Voltages
1, 3, 5, 6, 8
2
4
V
V2
V4
13.5
1.6
1.5
V
V
V
Junction temperature Tj150 °C
Ambient temperature Tamb -10 to +85 °C
Storage temperature range Tstg -50 to +150 °C
Thermal Resistance
Parameters Symbol Value Unit
Junction ambient
DIP8
SO8 on PC-board
SO8 on ceramic
SO8 on ceramic with
thermal compound
RthJA
RthJA
RthJA
RthJA
120
220
140
80
K/W
K/W
K/W
K/W
8U2403B
4776A–INDCO–11/03
Electrical Characteristics
VS = 6 V, Tamb = 25°C, reference point pin 7 (GND), unless otherwise specified.
Parameters Test Conditions Pin Symbol Min. Typ. Max. Unit
Supply voltage limitation IS = 4 mA
IS = 20 mA
6
6
VS
VS
12.5
12.6
13.5
13.7
V
V
Supply current VS = 6 V IS1.4 2.2 V
Voltage Monitoring 6
Turn-on threshold VTON 2.8 3.5 V
Turn-off threshold VTOFF 2.5 3.2 V
Charge-mode Indicator (LED) 8
LED current I83.0 6.0 mA
LED saturation voltage I8 = 3.7 mA V8960 mV
Leakage current Ilkg -0.35 1.1 µA
Collector Terminal, Figure 6 on page 10 1
Open-collector current ICO 15 55 µA
Saturation threshold VS = 6 V VTON
VTOFF
2.55
VS - 1 V
3.0
VS
3.35
VS - 0.4 V
V
V
Shunt emitter current R3 = 5.6 W 2I
2250 285 mA
Operational Sense Amplifier, Figure 1 on page 2 3
Input current V3 = 0 V I3-0.6 0.08 µA
Input voltage
VRef = 1.5 V
VRef = 100 mV
VRef = 0 V
V3
V3
V3
1.42
40
-0.4
1.5
70
1.58
100
40
V
mV
mV
Oscillator 4
Leakage current V4 = 0 to 0.85 V Ilkg -0.5 0.1 µA
Threshold voltage Upper VT(u) 875 985 mV
Oscillator frequency R4 = 160 kW, C4 = 2.2 nF
R4 = 680 kW, C4 = 4.7 nF
fosc
fosc
2700
305
3050
345
Hz
Hz
Test Mode Switch (STM)5
Input current V5 = 6 V
V5 = 0 V
I5
I5
40
-75
120
- 20
µA
µA
Output voltage High
Low
V0(H)
V0(L)
1.7
0.5
2.5
1.0
V
V
9
U2403B
4776A–INDCO–11/03
Internal Temperature
Switch
The internal temperature monitoring is active if the chip temperature rises above 140°C.
Above this temperature, the voltage at pin 3 returns to zero. Similarly, the charge cur-
rent, Ich, reduces according to the equation:
Ich = V3/R3
where Ich = 1 to 2 mA (IC supply current)
The oscillator is connected to GND via pin 3 (V3) which holds the present time status.
When the chip temperature decreases below the transition value, all functions are
released and the charge time is continued. The process is reversible. If there is a higher
power dissipation in the circuit (Tj > 140°C), the temperature monitoring remains perma-
nently activated (ON). The total cycle time is prolonged according to the interrupt-time
duration, see Figure 5.
Automatic Control
Protection
To reduce design costs, it is possible to select a transformer that requires minimum
power supply.
The output stage of the control is selected so that it is switched off before saturation is
achieved (VCEsat = 3.0 V). In this case, the voltage at pin 3 is kept at a value of zero. The
charge current is also zero, and the transformer is now an open-circuit impedance. The
system becomes active again if V1 ³ VS.
The advantage of the system is that if sags of short duration appear on the mains volt-
age, or if the transformers used are too small, the charge duration will be increased, but
the charge capacity remains the same, see Figure 6 on page 10.
Figure 5. Charge Duration - Overtemperature
130°C
Tj
I1
Charge current
Timing
Charge mode Counting timer t
140°C
Tj
10 U2403B
4776A–INDCO–11/03
Figure 6. Charge Duration – V1
Standard Applications
Basic Example
Special Requirements of
Different Charge Times
3.0 V
0 V
Charge current
Timing
-V1
Charge mode Counting timer t
VS
I1
NiCd battery 750 mAh
Charging time: 3 h
Charge current:
240 mA, 1/3 C
Trickle charge:
19 mA < 1/40 C
R1 = 510 W, 1/8 W
C1 = 47 µF/ 16 V
R3 = 6.2 W, 1/2 W
R4 = 300 kW
C4 = 470 pF
R5 = 8.2 W, 1/2 W
Table 2. Minimum Supply Voltage
Number of Cells DC Supply Minimum
1 6.8 V
2 8.3 V
3 9.8 V
4 11.3 V
5 12.8 V
Table 3. R4, C4 Values for Different Charging Times
Components 2 h 4 h 6 h 7 h 12 h
R4300 kW430 kW470 kW470 kW390 kW
C4330 pF 470 pF 680 pF 1 nF 2.2 nF
11
U2403B
4776A–INDCO–11/03
Special Requirements for
Different Charge
Currents
Basic Equations R1 = 0.5 V/IS
IS = 1.8 mA
R5 = V5/(Ich - 20 mA)
Nominal Charge Current Ich = V3/R3 where V3 = 1.48 V (typically)
Trickle Current:
Ich = V3/R3 + I8 + IS
Typical values are:
V3 = 100 mV, I8 = 4.5 mA
Figure 7. Standard Application
Table 4. R3, R5 Values for Different Charge Currents
Components 240 mA 150 mA 100 mA 50 mA
R36.2 W10 W15 W30 W
R58.2 W15 W22 W68 W
8765
123
4
Charge
R1
DC
supply
U2403B
READY
LED1
IS
C1
R4
R3C4
LED2
R5
Ich
12 U2403B
4776A–INDCO–11/03
Booster and Trickle Charge Reduction
Basic Example
Special Requirements of
Different Charge Times
Special Requirements for
Different Charge
Currents
R6 = 560 W, reduced trickle charge
Basic Equations R1 = 0.5 V/IS
R5 = V(LED2)/(Ich - 20 mA)
Nominal Charge Current Ich = V3/R3
V3 = 1.48 V, typically
NiCd battery 1000 mAh
Charging time: 2 h
Charge current: 500 mA
Trickle charge:
22 mA < 1/22 C
R1 = 510 W, 1/8 W
C1 = 1000 µF/ 16 V
R3 = 3 W, 1 W
R4 = 300 kW
C4 = 330 pF
R5 = 3.9 W, 1 W
C2 = 1 µF
Table 5. Supply Voltage
Number of Cells DC Supply Minimum
1 6.5 V
2 8.0 V
3 9.5 V
4 11.0 V
5 12.5 V
Table 6. R4, C4 Values for Different Charge Times
Components 2 h 4 h 6 h 7 h 12 h
R4300 kW430 kW470 kW470 kW390 kW
C4330 pF 470 pF 680 pF 1 nF 2.2 nF
Table 7. R3, R5 Values for Different Charge Currents
Components 616 mA 493 mA 411 mA 296 mA
R32.4 W3 W3.6 W5 W
R53.9 W3.9 W4.7 W6.8 W
13
U2403B
4776A–INDCO–11/03
Trickle Current: Ich = V3/R3 + ILED1 + IS - I6
Typical values:
V3 = 100 mV
ILED1 = 4.5 mA
IS = 1.8 mA
Trickle-charge Reduction (I6)I6 = (VBatt + VD1)/R6VD1 = 0.75 V
Figure 8. Application for Charge Current > 250 mA
To meet the requirements of higher charge currents, an external booster transistor can
be used (see Figure 8). As the temperature cannot be monitored in this case, a heat
sink with a resonable size should be used for safe operation. The test mode switch S1
can be used for accelerated production check.
Charge System at Higher
Voltage up to 30 V
Charge systems with higher voltages than VSmax can be realized with the additional
expander circuitry, as shown in Figure 9 on page 14. This circuit contains a simple tem-
perature monitoring function. When the temperature level is reached, the transistor, T3,
is switched on. If T3 is switched on and there is current flow into pin 5, normal charge is
terminated.
8765
1234
Charge
R5
DC
supply
U2403B
READY
BYW52
BD 136
or
BC 636
S1
S1: use for test only
LED1IS
10 kΩ
LED2
R3
R4
C4
C2R2
Ich
R6
I6
D1R1C1
14 U2403B
4776A–INDCO–11/03
Figure 9. U2403B for Higher Supply Voltage up to 30 V with Integrated Temperature Monitoring
8765
1234
U2403B
red
LED1 normal charge
LED2 trickle charge
mounted
on
heatsink
green
LED1
LED2
NTC
R11
Battery
+
-
DC-Supply
30 V
+
-
Ich
R1 = 1 kΩ, R2= 10 kΩ, R3 = f(IC), R4 = f(time), R5 = 13Ω/0.5W, R6 = 1kΩ
R7 = 10 kΩ, R8 = 47 kΩ, R10 = 10 kΩ, R11 = f(temp.), D1 = 1N4148
D2 = BZX85C10,
R10
T3
R8
D1
D2
R2
R1
T2
T1
R5R7R6
C2
R4
C4
R3
C1 = 110 µF/6 V, C2 = 10 nF, C4 = 330 pF
R11 f(temp.) depends on number of cells
Table 8. Value of R11 for Different Number of Cells
Number of Cells R11
2
3
4
5
13 kW
8.2 kW
6.2 kW
4.7 kW
Table 9. NTC Resistance at Different Temperatures
NTC Value NTC Resistance
25°C
40°C
50°C
6.8 kW
3.9 kW
2.8 kW
15
U2403B
4776A–INDCO–11/03
Package Information
Ordering Information
Extended Type Number Package Remarks
U2403B-x DIP8 Tube
U2403B-xFP SO8 Tube
U2403B-xFPG3 SO8 Taped and reeled
9.8
9.5
Package DIP8
Dimensions in mm
1.64
1.44
4.8 max
0.5 min 3.3
0.58
0.48
7.62
2.54
6.4 max
0.36 max
9.8
8.2
7.77
7.47
85
14
technical drawings
according to DIN
specifications
16 U2403B
4776A–INDCO–11/03
technical drawings
according to DIN
specifications
Package SO8
Dimensions in mm 5.00
4.85
0.4
1.27
3.81
1.4
0.25
0.10
5.2
4.8
3.7
3.8
6.15
5.85
0.2
85
14
Printed on recycled paper.
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does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are
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4776A–INDCO–11/03
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