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U6046B_05 Datasheet, PDF (4/16 Pages) ATMEL Corporation – REAR WINDOW HEATING TIMER / LONG-TERM TIMER
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Figure 3-2. Basic Circuit for VS = 5V
VS = 5 V
C2
R2
VBatt
8
7
6
5
U6046B
1
2
3
4
3.2 Oscillator (Pin 6)
The external components R2 and C2 determine the oscillator frequency. The capacitor C2 is
charged by R2 and discharged by an integrated 2-kΩ resistor.
A stable oscillator frequency with minimal influence of the temperature coefficient of the inte-
grated resistor is achieved with R2 >> 2 kΩ.
Oscillator frequency, f, is calculated as follows:
f = -------1-------
t1 + t2
where
t1 = charge time = α1 × R2 × C2
t2 = discharge time = α2 × 2 kΩ × C2
α1 and α2 are constants as such
α1 = 0.833 and α2 = 1.551 when C2 = 470 pF to 10 nF
α1 = 0.746 and α2 = 1.284 when C2 = 10 nF to 4700 nF
The debounce time, t3, and the delay time, td, depend on the oscillator frequency, f, as follows:
t3
=
6×
-1-
f
td
=
73728 ×
1--
f
Table 6-1 on page 10 shows relationships between t3, td, C2, R2 and frequencies from 1 Hz to 20
kHz.
4 U6046B
4674B–AUTO–09/05
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