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U6032B Datasheet, PDF (4/12 Pages) ATMEL Corporation – AUTOMOTIVE TOGGLE SWITCH IC
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Figure 4. Basic Circuit for VS = 5 V
VS = 5 V
VBatt
C2
R2
8
7
6
5
U6032B
1
2
3
4
Oscillator, Pin 6
The oscillator frequency, f, is determined mainly by the R2C2 circuit. The resistance, R2,
determines the charge time, and the integrated resistance (2 kW) 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 kW), as
the temperature response and the tolerances of the integrated resistance are consider-
ably greater than the external resistance value.
The 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, e.g.:
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, depends on the oscillator frequency, f, as follows:
t3
=
6
´
1--
t
Table 1 shows the relationship between t3, C2, R2 and frequencies from 1 Hz to 20 kHz.
4 U6032B
4771A–AUTO–11/03
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