U2640B
Intemittent- and Wipe/ Wash Control for Wiper Systems
Description
With the U264xB, Atmel Wireless & Microcontrollers
developed a family of intermittent- and wipe/wash con-
trol circuits for windshield or backlite wiper systems with
identical basic functions. The circuit design provides the
possibility to generate ”x” versions using different metal-
lization masks. Thus, it is easy to verify a broad range of
time sequences which can be set independently of each
other.
Features
D
Relay activation can be controlled by a limit switch of
the wiper motor or by a fixed activation period for
systems without limit switch
D
Debounced input stages
D
Enable/disable of pre-wash delay by program pin
D
Polarity of WIWA: V
Batt
D
Polarity of INT:
V
Batt
D
Relay output is protected with a clamping diode
D
Relay activation:
D
Interval pause:
D
After wiping:
D
Pre-wash delay:
0.48 s
5.8 s
5.2 s
0.52 s
D
Wipe/wash mode with priority
D
Protected in accordance to ISO/TR 7637–1
D
EMC with intergrated filters
Block Diagram
VS
OSC
Voltage
stabilization
and
POR
Oscillator
INT
21 V
WIWA
21 V
LS
21 V
PP
21 V
Input
comparator
Logic
Load-
dump
detection
and
output
control
Open-collector
relay driver
REL
21 V
GND
13944
Figure 1. Block diagram
Ordering Information
Extended Type Number
U2640B
U2640B–FP
Package
DIP8
SO8
Remarks
Rev. A4, 03-Apr-01
1 (10)
U2640B
Pin Configuration
Pin
1
2
3
4
5
6
7
8
Symbol
INT
WIWA
LS
PP
GND
REL
V
S
OSC
Function
Intermittent input
Wipe/wash (WIWA) input
Limit switch (wiper motor) input
Program pin
Ground
Relay output
Supply voltage
RC oscillator input
Figure 2. Pinning
INT
WIWA
LS
PP
1
2
3
4
8
7
6
5
OSC
V
S
REL
GND
13365
Functional Description
All times specified below refer to an oscillator frequency
of 200 Hz. Figures 9 to 16 show the dependencies of the
times upon battery voltage and temperature. The
temperature dependence of the oscillator frequency is
essentially determined by the temperature coefficient of
the oscillator capacitor. The temperature dependence of
the oscillator frequency can be reduced to minimum with
a slightly negative temperature coefficient (N100). The
capacitor used in figures 10 and 11 has a slightly positive
temperatur coefficient.
All times are permanently set and can be changed only
jointly within certain limits by adjusting the oscillator
frequency. See table 1.
Interval Pause
The interval pause t
INT
= 5.8 s follows t
ON
. Opening of
switch
INT
causes a debounce time, t
D
, and reclosing
results in the relay on-time, t
ON
, after t
D
.
Wipe/Wash Function without Pre-Wash
Delay (PP connected to GND)
The water pump is switched on when the switch
WIWA
is pressed and, after the debounce time, t
D
, the relay is
energized. After-wiping time t
AW
= 5.2 s starts as soon as
switch
WIWA
is opened and the debounce time, t
D
, has
expired. If the limit switch is connected, the relay remains
energized until the wiper arm returns to park position, i.e.,
the motor current flows via the relay contact only.
Intermittent Function
The relay is energized for the time t
ON
after the switch
INT is switched on with respect to V
Batt
and after expira-
tion of time t
D
(debounce).
The debounce time ranges between 60 ms and 80 ms. A
time period of 5 ms to 40 ms for internal sequence control
must be added (asynchronism between operating instant
and internal clock) e.g., the response time may range from
65 ms up to 120 ms.
If the limit switch of the windscreen wiper motor is
connected to Pin
LS,
the relay is energized as long as the
switch is at high potential, regardless of the relay on-time,
t
ON
, i.e., the motor current in interval mode flows via the
relay contact only. In park position, the motor winding at
both ends is connected to ground via the limit switch and
the motor is decelerated immediately. The limit switch
input is debounced with t
DL
= 17 ms.
The relay on-time, t
ON
, always elapses – even if the
interval switch was opened beforehand.
Wipe/Wash Function with Pre-Wash Delay
(PP connected to V
S
)
In wipe/wash mode, the relay is energized after a delay
time. The water pump can spray water onto the wind-
screen during the delay time, t
DEL
.
The on-delay time of the U2640B is:
t
DEL
= t
D
+ 0.44 s = 0.52 s
If switch
WIWA
is closed longer than t
D
but shorter than
t
DEL
, the after-wiping time, t
AW
, starts after expiration of
t
DEL
. The wipe/wash function with or without on-delay
t
DEL
can be selected by programming PP.
PP connected to GND:
PP connected to V
S
:
without pre-wash delay
with pre-wash delay
The after-wiping time, t
AW
, is re-triggerable in both cases.
2 (10)
Rev. A4, 03-Apr-01
U2640B
Intermittent and Wipe/Wash Mode
The wipe/wash function has priority over the interval
function. If switch
WIWA
is closed during the interval
function, wipe/wash mode is activated immediately after
the debounce time, t
D
, even if an on-delay is programmed
(t
DEL
= 0 s). Expiry of t
AW
is directly followed by the next
relay on-time, t
ON
, of intermittent mode.
Power Supply
For reasons related to protection against interference and
destruction, the Pin V
S
must be provided with an RC net-
work for limiting the current in the event of overvoltage
and for buffering in the event of voltage drops.
Proposed ratings: R
V
= 510
W,
C
V
= 47
mF.
An integrated
14-V Zener diode is connected between V
S
and GND.
Oscillator
All timing sequences are derived from an RC-oscillator
whose charging time, t
1
, is determined by an external
resistor, R
OSC,
and whose discharging time, t
2,
is
determinated by an integrated 2-kW resistor. Since
tolerance and temperature response of the integrated
resistor are far higher than those of the external resistor,
t
1
/t
2
must be selected to be greater than 20 for stability
reasons. The minimum value of R
OSC
should not be less
than 68 kW.
Calculating cycle duration and frequency:
t = t
1
+ t
2
= C
OSC
f
OSC
= 1/t
( 0.74
R
OSC
+ 2260
W)
Interference Voltages and Load-Dump
In the case of transients, the integrated Zener diode limits
the voltage of the relay output to approximately 28 V. In
the case of load-dump, a current (dependent upon R
V
and
C
V
) flows through the integrated 14-V Zener diode, and
the relay output is switched on at V
Batt
> 30 V in order to
avoid destruction of the output. The output transistor is
rated such that it can withstand the current generated dur-
ing the load-dump through the relay coil. In practice, the
windscreen wiper motor is switched on via the relay and
thus the amplitude of the load-dump pulse is limited. The
supply voltage of the circuit is limited to 14 V by the inte-
grated Zener diode, and the inputs are protected by
external protective resistors and integrated Zener diodes.
RF suppression is implemented with a low-pass filter at
the inputs, consisting of a protective resistor and the inte-
grated capacitor.
and
Calculating the capacitor for a given resistor:
C
OSC
= t / ( 0.74
R
OSC
+ 2260
W)
Calculating the oscillator resistance for a given capacitor:
R
OSC
= 1.34
( t / C
OSC
– 2260
W)
Recommended frequency: f
OSC
= 200 Hz
(for R
OSC
= 200 kW, C
OSC
= 33 nF)
All times can be varied jointly within specific limits by
varying the oscillator frequency (see table 1). The oscilla-
tor is operable up to 50 Hz.
Table 1 Change in times by varying the oscillator frquency
f
osc (Hz)
100
120
140
160
180
200
220
240
260
280
300
400
t
D
[ms]
140
116
100
87
77
70
64
58
54
50
46
35
t
DL
[ms]
35
29
25
22
19
17
16
14
13
12
11
9
Power-on Reset (POR)
When the supply voltage is applied, a power-on reset
pulse is generated which sets the circuit’s logic to a
defined initial state. The POR threshold is approximately
V
S
= 4.3 V.
t
ON
[ms]
960
800
686
600
533
480
436
400
370
343
320
240
t
INT
[s]
11.84
9.68
8.45
7.40
6.57
5.92
5.38
4.93
4.55
4.23
3.95
2.96
t
AW
[s]
10.24
8.53
7.31
6.40
5.68
5.12
4.65
4.26
3.94
3.66
3.41
2.56
t
DEL
[s]
920
766
657
575
511
460
418
383
353
328
306
230
Rev. A4, 03-Apr-01
3 (10)
U2640B
Absolute Maximum Ratings
With recommended external circuitry
Parameter
Test Conditions
Supply voltage (static)
5 min
Supply current pulse
Supply current pulse
Relay output current (static)
Relay output current pulse
Ambient temperature range
Storage temperature range
Power dissipation
Power dissipation
DIP8
SO8
300 ms
2 ms
300 ms
Symbol
V
Batt
I
S
I
S
I
REL
I
REL
T
amb
T
stg
P
tot
P
tot
Value
24
1.5
150
300
1.5
–40 to +95
–55 to +125
0.45
0.34
Unit
V
A
mA
mA
A
°C
°C
W
W
Thermal Resistance
Parameters
Junction ambient
Junction ambient
DIP8
SO8
Symbol
R
thJA
R
thJA
Value
120
160
Unit
K/W
K/W
Electrical Characteristics
Reference point Ground GND, T
amb
= 25_C, V
Batt
= 13.5 V, unless otherwise specified (see figures 11 and 12)
Parameters
Voltage supply
Supply voltage
Supply current
Undervoltage threshold
(POR)
Internal Z-diode
Internal capacitor
Series resistance
Filter capacitor
Oscillator input OSC
Internal discharge resistor
Lower switching-point
voltage
Upper switching-point
voltage
Input current
Oscillator frequency
Test Conditions / Pin
Pin 7
Symbol
V
Batt
I
S
V
S
V
Z
C
S
R
V
C
V
Pin 8
R
DIS
V
OSC
V
OSC
V
OSC
= 0 V
–I
OSC
f
OSC
1.3
2.0
3.2
0.16 V
S
0.20 V
S
0.24 V
S
0.55
V
S
0.60
V
S
0.65
V
S
kW
V
V
mA
Hz
Min
6.0
0.5
3.0
13.5
Typ
Max
16.0
3.0
5.1
16.2
Unit
V
mA
V
V
pF
W
mF
2.0
14.0
15
510
47
1
200
2
50 k
Note: All internally generated time sequences are derived from the oscillator frquency. The tolerances refer to a
frequency adjusted to f
OSC
= 200 Hz.
4 (10)
Rev. A4, 03-Apr-01
U2640B
Electrical Characteristics (continued)
Reference point Ground GND, T
amb
= 25_C, V
Batt
= 13.5 V, unless otherwise specified (see figures 11 and 12)
Parameters
Test Conditions / Pin
Symbol
Input limit switch LS
Pin 3
Internal protection-diode
I
LS
= 10 mA
V
LS
voltage
Internal capacitor
C
LS
Switching threshold
V
LS
voltage
Input current
V
LS
= V
S
I
LS
Internal pull-up resistor
R
LS
External protection resistor
R
S
Inputs INT, WIWA and PP
Pins 1, 2 and 4
Internal protection-diode
I
E
= 10 mA
V
E
voltage
Internal capacitor
C
E
Switching threshold
V
E
voltage
Input current
V
E
= 0 V
–I
E
Internal pull-down resistor
R
E
External protection resistor
R
S
Relay output
Pin 6
Saturation voltage
I = 100 mA
V
REL
Saturation voltage
I = 200 mA
V
REL
Z-diode clamp voltage
I = 10 mA
V
REL
Leakage current
V = 14 V
I
REL
Relay coil resistance
R
REL
Load-dump protection
V
Batt
threshold
Internal pulse times
Debouncing period inputs INT/WIWA 12 - 16 clocks
t
D
Debouncing period inputs LS
3 – 4 clocks
t
DL
Relay activation time
96 clocks
t
ON
Intermittent pause
t
INT
After wiping period
1024
"
68 clocks
t
WIWA
Pre-wash delay, reaction
88 – 96 clocks
t
DEL
time for switch-on delay =
t
DEL
+ t
D
Min
19.5
Typ
21.0
25
0.375 V
S
0.5 V
S
0.675 V
S
Max
25.5
Unit
V
pF
V
mA
kW
kW
V
pF
V
mA
kW
kW
V
V
V
mA
W
V
13
10
19.5
20
1
27
21.0
25
25.5
0.375 V
S
0.5 V
S
0.675 V
S
13
10
20
1
27
19.5
60
28
21.0
1.1
1.5
25.5
12
42
33
60
15
70
17.5
480
5.92
80
20
4.78
440
5.46
480
ms
ms
ms
s
s
ms
Note: All internally generated time sequences are derived from the oscillator frquency. The tolerances refer to a
frequency adjusted to f
OSC
= 200 Hz.
Rev. A4, 03-Apr-01
5 (10)
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