U6046B Datasheet, PDF (4/13 Pages) TEMIC Semiconductors – Rear Window Heating Timer

Oscillator (Pin 6)
Relay Control Output
(OUT)
Interference Voltages
and Load-dump
Power-on Reset
The external components R₂ and C₂ determine the oscillator frequency. The capacitor
C₂ is charged by R₂ and discharged by an integrated 2-kW resistor.
A stable oscillator frequency with minimal influence of the temperature coefficient of the
integrated resistor is achieved with R₂ >> 2 kW.
Oscillator frequency, f, is calculated as follows:
f = -------¹-------
t₁ + t₂
where
t₁ = charge time = a₁ ´ R₂ ´ C₂
t₂ = discharge time = a₂ ´ 2 kW ´ C₂
a₁ and a₂ are constants as such
a₁ = 0.833 and a₂ = 1.551 when C₂ = 470 pF to 10 nF
a₁ = 0.746 and a₂ = 1.284 when C₂ = 10 nF to 4700 nF
The debounce time, t₃, and the delay time, t_d, depend on the oscillator frequency, f, as
follows:
t₃
=
6
´
-¹-
f
t_d
=
73728
´
-¹-
f
Table 1 shows relationships between t₃, t_d, C₂, R₂ and frequencies from 1 Hz to 20 kHz.
The relay control output is an open-collector Darlington circuit with an integrated 23-V
Z-diode to limit the inductive cut-off pulse of the relay coil. The maximum static collector
current must not exceed 300 mA and saturation voltage is typically 1.1 V at 200 mA.
The lC supply is protected by R₁, C₁, and an integrated Z-diode, while the inputs are
protected by a series resistor, integrated Z-diode and RF capacitor (see Figure 8).
The relay control output is protected via the integrated 23-V Z-diode in the case of short
interference peaks. It is switched to a conductive condition for a battery voltage of
greater than approximate 40 V in the case of a load-dump. The output transistor is
dimensioned so that it can withstand the current produced.
When the operating voltage is switched on, an internal power-on reset pulse (POR) is
generated which sets the logic of the circuits to a defined initial condition. The relay out-
put is disabled.
4 U6046B
4674A–AUTO–01/03