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U6032B_05 Datasheet, PDF (4/12 Pages) ATMEL Corporation – Automotive Toggle Switch IC
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Figure 4-2. Basic Circuit for VS = 5 V
VS = 5 V
VBatt
C2
R2
8
7
6
5
U6032B
1
2
3
4
4.2 Oscillator, Pin 6
The oscillator frequency, f, is determined mainly by the R2C2 circuit. The resistance, R2, deter-
mines the charge time, and the integrated resistance (2 kΩ) is responsible for the discharge
time. To ensure the stability of the oscillator frequency, it is recommended that the selected R2
value is remarkably greater than the internal resistance (2 kΩ), as the temperature response and
the tolerances of the integrated resistance are considerably greater than the external resistance
value.
The 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, e.g.:
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, depends on the oscillator frequency, f, as follows:
t3
=
6×
1--
t
Table 7-1 on page 8 shows the relationship between t3, C2, R2 and frequencies from 1 Hz to
20 kHz.
4 U6032B
4771B–AUTO–11/05
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