U2044B_08 Datasheet, PDF (4/9 Pages) ATMEL Corporation – Dual Output Flasher

3. Functional Description
3.1 Oscillator (Pin 1 and 14)
Flashing frequency, f₁, is determined by the R₁C₁ components as follows (see Figure 1-1 on
page 2):
f₁ ≈
-----------------¹-------------------
R₁ × C₁ × 1.5
Hz
where
C₁ ≤ 47 µF
R₁ = 6.8 kΩ to 180 kΩ
In the case of a lamp outage, the oscillator frequency is switched to the lamp outage frequency
f₂ with f₂ ≈ 2.2 × f₁.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode:
40% (bright phase)
3.2 Start Input Right and Left (Pin 2 and 3)
Flashing is disabled as long as the input comparator is tied to GND (pull-down resistor R₇ or R₅).
The high-side flasher switch left or right changes the comparator status and enables the output
stage at pin 11 or pin 13. R₆ and R₄ are protection resistors for the input stage.
With an open flasher switch the current consumption is only I < 10 µA. The IC is kept in stand-by
mode until there is a voltage drop of V ≈ 6.9V at the pull-down resistor.
Direction mode can only be activated when the ignition switch is in the ON-position as shown in
Figure 1-1 on page 2.
3.3 Start Input Hazard Warning (Pin 4)
In contrast to the direction switches, the hazard input is a low-side type. The pull-up resistor R₁₀
provides the off-state. R₃ is a protection resistor for the input stage. Hazard warning can be acti-
vated independent of the ignition switch position.
3.4 Supply Voltage Sense (Pin 5)
This pin supplies the lamp outage comparator at pin 8 and is externally connected to the battery
(Kl 30).
3.5 Control Input Relay 1 and 2 (Pin 6 and 7)
The feedback detects the bright phase and the dark phase and enables the oscillator.
4 U2044B
4721C–AUTO–02/08