U641B_05 Datasheet, PDF (4/12 Pages) ATMEL Corporation – Interval and Wipe/Wash Wiper Control IC with Delay

4. Circuit Description
4.1 Interval Function, Pin 2
By closing the interval switch, S₂, to supply voltage, V_Batt, the relay is activated. The internal cur-
rent source (pin 3) which holds the capacitor C₂ in charged state is switched-off. As soon as
there is a positive potential at the park switch (S₁), current source F (see Figure 2-1 on page 2)
charges the capacitor C₂ very quickly. After the wiper operation is finished, S₁ is again at ground
potential, the relay is in the off position - interval pause begins - the capacitor C₂ is discharged
through the current source C, till the voltage at pin 3 is below the threshold of 2V. Interval pause
can be adjusted between 4 s to 20 s with the help of potentiometer R₃. Now the relay switches
on and the next interval cycle begins. Opening switch S₂ causes current source A to discharge
C₂ immediately and current sources C and F are switched off.
4.2 Wipe/Wash (WIWA) Operation, Pin 5
By closing the WIWA switch, S₃, to supply voltage, V_Batt, the water pump starts spraying the
water on the windshield. During this function, the current source A is switched-off which keeps
the capacitor C₂ in a discharged state. Now the capacitor is charged through the current source
F. If (after a time interval of approximately 600 ms) the voltage at the capacitor is greater than
6.1V, the relay is turned on as long as the switch WIWA is closed.
The after-wiping time begins when the switch is open, the sources D and F are switched off and
the source E is activated. Source E discharges the capacitor until the voltage is less than 2.2V.
The relay is off and the wiper-motor is supplied via the park switch until the park position is
reached. The after-wiping time is determined by the current source E which can be regulated
with the external resistor R_Time. When the after-wiping time has elapsed, the source A dis-
charges the capacitor. The relay switch is independent of the park switch S₁.
4.3 Interval and WIWA Functions
The interval function is interrupted immediately when the switch S₂ is activated. The current
source A discharges the capacitor to a value of 2V, afterwards, the normal wash function starts.
Interval wiping starts immediately when the after-wipe time is over. The switching delays are
slightly shorter, because the capacitor is already charged to a value of 2V.
The Wipe/Wash function is not interrupted when the interval switch S₂ is activated. The interval
function begins after the WIWA function has elapsed.
4 U641B
4773B–AUTO–09/05