Features
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Interval Pause: 4 to 20 s
After-wiping Time: 2 to 20 s
Wiper Motor's Park Switch
Wipe/Wash Mode Priority
One External Capacitor Determines All Time Sequences
Relay Driver with Z-diode
Interference Protection According to VDE 0839 or ISO/TR 7637/1
Load-dump Protected
Description
The U642B is a bi-polar integrated circuit designed for the wiper application in the
automotive market. It includes wipe, wash and internal mode.
Functional Description
As a convenience feature of the windshield wiper, intermittent and wipe/wash opera-
tion fuctions are implemented in most of the automobiles. The U642B is a
cost-effective solution for an accurate timing function control. Wipe/wash mode has
priority over interval mode. Interval pause and after-wiping time can be set to fixed val-
ues by using resistors in a broad time range. Added value can be provided with an
individual, continuous adjustment of the interval pause by a potentiometer which may
be built into the stalk. For proper operation, it is mandatory to feed the signal of the
wiper motor's park switch into U642B.
Figure 1.
Block Diagram
V
S
8
OUT
7
PARK
6
V
Ref
Park switch
comparator
WASH
5
V
Ref
Input
comparator
Interval- and
Wipe/Wash
Wiper Control
IC
U642B
Load-dump
comparator
V
Ref
Logic
V
Ref
Wipe/wash
comparator
Interval
comparator
A
B
C
D
E
F
1
GND
2
INT
3
C
t
4
R
t
Rev. 4774A–AUTO–11/03
U642B
Circuit Description
Interval Function, Pin 2
By closing the interval switch, S
2
, to supply voltage, V
Batt
, the relay is activated. The
internal current source (pin 3) which holds the capacitor C
2
in a charged state is
switched-off. As soon as there is a positive potential at the park switch (S
1
), the current
source F (see Figure 1 on page 1) charges the capacitor C
2
very quickly. After the wiper
operation is finished, S
1
is again at ground potential, the relay is in the off position - inter-
val pause begins - the capacitor C
2
is discharged through the current source C, till the
voltage at pin 3 is below the threshold of 2 V. Interval pause can be adjusted between
4 s to 20 s with the help of potentiometer R
3
. Now the relay switches on and the next
interval cycle begins. Opening of switch S
2
causes the current source A to discharge C
2
immediately and current sources C and F are switched-off.
Wipe/Wash (WIWA)
Operation, Pin 5
By closing the WIWA switch, S
3
, to supply voltage, V
Batt
, the water pump starts spraying
water on the windshield. During this function, the current source A is switched-off which
keeps the capacitor C
2
in a discharged state. Now the capacitor is charged through the
current sources D and F. If (after a time interval of approximately 100 ms) the voltage at
the capacitor is greater than 6.5 V, 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 2.2 V. 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 discharges the capacitor. The relay switch is independent of the
park switch S
1
.
Interval and WIWA
Functions
The interval function is interrupted immediately when the wipe/wash mode is activated.
The current source A discharges the capacitor to a value of 2 V, 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 2 V.
The wipe/wash function is not interrupted when the interval switch S
2
is activated. The
interval function begins after the WIWA function has elapsed.
3
4774A–AUTO–11/03
U642B
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameters
Supply voltage t = 60 s, terminal 15
Supply current
t = 2 ms
t = 200 ms
Relay control output current (DC)
t = 200 ms
Park switch, S
1
Wipe/Wash switch, S
3
Interval switch, S
2
Power dissipation T
amb
= 90°C
Storage temperature range
Ambient temperature range
Pin
8
8
Symbol
V
Batt
I
8
I
8
I
7
I
7
I
6
I
5
I
2
P
tot
T
stg
T
amb
Value
28
1.5
150
200
1.2
50
50
50
500
-55 to +125
-40 to +85
Unit
V
A
mA
mA
A
7
Pulse Current (Control Inputs) t = 200 ms
6
5
2
mA
mW
°C
°C
Thermal Resistance
Parameters
Junction ambient
DIP8
SO8
Symbol
R
thJA
R
thJA
Value
120
160
Unit
K/W
K/W
5
4774A–AUTO–11/03
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