ATMEL U642B Datasheet
U642B
Rev. A4, 10-Apr-01 1 (7)
Interval- and Wipe/ Wash Wiper Control IC
Description
As a convenience feature of the windshield wiper
intermittent and wipe/wash operation are implemented in
most of the automobiles. The U642B is the low-cost
solution for an accurate timing function control.
Wipe/wash mode has priority over interval mode. Interval
pause and afterwiping time can be set to fixed values 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.
Features
Interval pause: 4 to 20 s
Afterwiping 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
Block Diagram
Wipe / wash
comparator
Interval
comparator
Load-dump
comparator
V
Ref
V
Ref
V
Ref
Input
comparator
Park switch
comparator
V
Ref
8
7
6
5
4
1
23
ABC DEF
Logic
V
S
OUT PARK
WASH
R
t
GND INT
C
t
94 8950
Figure 1. Block diagram
U642B
Rev. A4, 10-Apr-012 (7)
Ordering Information
Extended Type Number Package Remarks
U642B DIP8
U642B–FP SO8
Pin Description
Pin Symbol Function
1 GND Ground
2 INT Interval switch
3 C
t
Timing capacitor C
2
4 R
t
Afterwiping time resistance
5 WASH Wipe/Wash switch
6 PARK Park switch for wiper motor
7 OUT Relay control output
8 V
S
Supply voltage KI. 15
V
S
OUT
WASH
GND
INT
R
t
C
t
1
2
3
4
8
7
6
5
U642B
93 7691
PARK
Figure 2. Pinning
Circuit Description
Interval Function, Pin 2
By closing the interval switch, S2, to supply voltage,
V
Batt
, the relay is activated. The internal current 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), the current source F (see figure 1)
charges the capacitor C2 very fast. After the wiper
operation is finished, S1 is again at ground potential, the
relay is in ”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 2 V.
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 of switch S
2
causes the current source A to discharge C2 immediately
and current sources C and F are switched-off.
Wipe/Wash (WIWA) Operation, Pin 5
By closing the WIWA-switch, S3, to supply voltage,
V
Batt
, the water pump starts spraying water on the windscreen, the current source A is switched-off which keeps
the capacitor C2 in discharged state. Now the capacitor is
charged through the current sources D and F, and when 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-wipe-time begins after the switch is open
whereas the sources D and F are switched off and the
source E is activated. Source E discharges the capacitor
till 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 will be reached. The after-wipe-time is
determined by the current source E which can be
regulated with the external resistor R
Time
. Afterwards the
source A discharges the capacitor. The relay switch off is
independent of the park switch S1.
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-wipetime 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 interval
switch S
2
is activated. Interval function begins after the
WIWA function is over.
U642B
Rev. A4, 10-Apr-01 3 (7)
1
2
6
5
8
7
3
4
10 k
10 k
R6R
5
C
1
47 F
10 V
R
2
C
2
22 F
10 V
R
4
R
time
= 130 k
R
1
510
10 k
R
3
S
2
S
3
MM
Relay
Park
switch
31
15
Wiper motor
Interval switch
Water pump
94 8951
S
1
WIWA
U642B
2.7 k
Figure 3. Application circuit with interval and wipe/wash operation
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