U2403B Datasheet, PDF (7/12 Pages) TEMIC Semiconductors – Charge Timer

U2403B
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 goes to zero. Similarly, the charge
current, I_ch, reduces according to the equation:
I_ch = V₃ / R₃
where I_ch = 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 (T_j > 140°C), the temperature monitoring remains
permanently activated (ON). The total cycle time is
prolonged according to the interrupt-time duration, see
figure 4.
Automatic Control Protection
To reduce the design costs, it is possible to select the trans-
former which requires minimum power supply.
The output stage of the control is selected so that
it is switched off before saturation is achieved
(V_CEsat = 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 ≥ V_S.
The advantage of the system is that if sags of short
duration appear on the mains voltage or if the trans-
formers used are too small, the charge duration is
increased, but the charge capacity remains the same (see
figure 5).
T_j
140°C
130°C
95 9640
T_j
Charge current
I₁
Timing
Charge mode
t
Counting timer
Figure 4. Charge duration – overtemperature
V_S
–V₁
3.0 V
0V
Charge current
I₁
Timing
Charge mode
Counting timer
Figure 5. Charge duration – V₁
TELEFUNKEN Semiconductors
Rev. A2, 14–Nov–96
95 9633
t
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