U840B
TELEFUNKEN Semiconductors
Rev. A2, 03-Feb-97
4 (8)
time t
2
runs off, one turn of the wiper arm is finished.
Afterwards it the interval mode can be immediatly
activated.
The resistor between the interval switch and Pin INT
determines the interval pause. The circuit U840B is so
dimensioned, that a linear resistor-time-characteristic is
used. Therefore, a doubling of the resistor evokes a doub-
ling ot the interval pause. With the help of the resistor R
3
the characteristic can be shifted parallel to its axis. The
resistors R
1
and R
2
keep their values.
An increasing of R
3
shifts the characteristic to longer
interval pauses. With it the interval pause can be adjusted
to the demanded values by the dimensioning of R
3
. The
resistor R
3
must not be smaller than l k , otherwise the
linearity of the resistor-time-characteristic cannot be
guaranteed and too great a current flows from the input
INT to GND.
Wipe/ Wash Releasing and Program Pin PP
After operating the wash button, the relay is activated
after the debouncing (Pin PP connects to V
S
). As long as
the button is pushed, water is sprayed on the windscreen
by the water pump. After releasing the wash button, after
100 ms reverse debouncing, the dry wiping time t
5
begins
to start. At the end of the dry wiping time the relay is
disabled.
The input PP is connected to ground, the debouncing time
of the WIWA mode is extended for 800 ms. The water is
sprayed on the windscreen before the wiper begins its job.
PP to GND: 0.8 s delay time
PP to V
S
:
Interval Wipe/Wash Mode
0.1 s delay time
The interval function is interrupted when the wash button
is operated. In this case, the 0.8 s delay time t
4
is reduced
to the 100 ms debouncing time. Interval function begins
after the wipe/ wash function is over.
Switch Contact Currents
The contact current of the interval switch is 0.6 to 3 mA.
Of course the current depends on the position of the
interval switches. The contact current of the wash button
is fixed by the internal resistance of the water pump. A
pull-down resistor is integrated at the input WASH.
Therefore, the input is connected to ground in the case of
an open wash push button and a pump which is not
connected.
Input Leakage Resistance
With a resistor more than 40 k between INT to GND the
interval function is not activated.
The wipe/ wash function is not activated by a leakage
resistance > 10 k and recommended external circuitry.
8
7
6
5
1
2
3
4
U840B
C1
47
μ
F
1.4 k
R3
C2
100 nF
39 k
R6
1.3 k
R1
2
1
4.7 k
3
2
1
2
1
R5
10 k
R4
180
Park
switch
M
Wiper
motor
M
Water
pump
VBatt
C
A
B
13286
Figure 3. Application circuit with interval and WIWA operation