U2405B Datasheet, PDF (9/17 Pages) TEMIC Semiconductors – Fast Charge Controller for Drained NiCd/NiMH Batteries

U2405B
Temperature Control, Figure 7
When the battery temperature is not inside the specified
temperature windows, the overal temperature control will
not allow the charge process. Sensor short circuit or
interruption also leads to switch-off.
Differentiation is made whether the battery exceeds the
maximum allowable temperature, T_max, during the
charge phase or the battery temperature is outside the
temperature window range before battery connection.
A permanent switch-off follows after a measurement
period of 20.48 s, if the temperature exceeds a specified
level, which is denoted by a status of a red LED₁. A charge
sequence will start only when the specified window
temperature range is attained. In such a case, the green
LED₂ starts blinking immediately showing a quasi charge
readiness, even though there is no charge current flow.
NTC sensors are normally used to control the temperature
of the battery pack. If the resistance values of NTC are
known for maximum and minimum conditions of
allowable temperature, then other resistance values, R_T1,
R_T2 and R_T3 are calculated as follows:
W suppose R_T2 = 100 k , then
+ R_T1
R_NTCmax
V_Ref – 4V
4V
+ R_T3
R_NTCmin
R_T2
R_T1
V_Ref
R_T1
NTC
sensor
V_Ref
14
R_T2
T_max
7
R_T3
7V
Sensor
8
7V
+
–
V_Ref = 4 V
+
–
Figure 7. Temperature window
High
temperature
Low
temperature
94 8682
TELEFUNKEN Semiconductors
Rev. A2, 14-Nov-96
9 (17)