U2402B Datasheet, PDF (7/17 Pages) TEMIC Semiconductors – Fast Charge Controller for NiCd/NiMH Batteries

U2402B
Battery Voltage Measurement
The battery voltage measurement at Pin 10
(ADC-converter) has a range of 0 V to 4 V, which means
a battery pack containing two cells can be connected
without a voltage divider.
w If the AD converter is overloaded (V_Batt 4 V) a safety
switch off occurs. The fast charge cycle is terminated by
automatically changing to the trickle charge.
Precaution should be taken that under specified charge
current conditions, the final voltage at the input of the
converter, Pin 10, should not exceed the threshold voltage
level of the reset comparator, which is 5 V. When the
battery is removed, the input (Pin 10) is terminated across
the pulled-up resistance, R_B1, to the value of
5 V-reset-threshold. In this way, the start of a new charge
sequence is guaranteed when a battery is reinserted.
If the battery voltage exceeds the converter range of 4 V,
adjusting it by the external voltage divider resistance, R_B2
and R_B3 is recommended.
Value of the resistance, R_B3 is calculated by assuming
R_B1 = 1 kW, R_B2 = 10 kW, as follows:
+ R_B3
R_B2
V_10max
V_Bmax – V_10max
The minimum supply voltage, V_smin, is calculated for
reset function after removing the inserted battery
according to:
+ ^{@ ǒ ) Ǔ ) ǒ ) ) Ǔ} V_smin
0.03mA R_B3 R_B1
R_B2 5V R_B1
R_B3
R_B2
R_B3
where:
V_10max = Max voltage at Pin 10
V_Smin = Min supply voltage at the IC (Pin 15)
V_Bmax = Max battery voltage
The voltage conditions mentioned above are measured
during charge current break (switch-off condition).
15 V_S
R_B1
V_DAC
- dV Recognition
–
+
I_ch
V_{B Battery}
R_B2
V_Ref =
12 mV ⁼
V_Batt
10
V_DAC ^{DAC control}
comparator
–
+
V₆
R_sh
R_B3
Reset
comparator
7V
V_Ref =
–
4.3 V
+
95 10174
Reset
V_Ref = 0.1 V
Figure 5. Input configuration for the battery voltage measurement
Table 1. valid when V_10max = 3.5 V
Cell No. 1
2
3
4
5
6
7
8
9
10 11 12
V_Smin (V) 8
R_B3 (kW)
–
8
8
9 11 13
15
17
19
21 23 25
– 51 16 10 7.5 5.6 4.7 3.9 3.3 3 2.7
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
7 (17)