ATMEL U2044B User Manual

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Dual Output Flasher

Description

The integrated circuit U2044B is used in relay-controlled
automotive flashers. With two output stages, each side of
the vehicle is controlled separately. A left and a right
direction indicator input with only a small control current
makes switch contacts for small loads possible.

Features

 Temperature and supply voltage compensated

flashing frequency

 Frequency doubling indicates lamp outage
 Two relay driver outputs with high current-carrying

capacity and low saturation voltage

U2044B

The separate hazard warning input simplifies the
construction of the hazard switch. Lamp outage is indi­cated by frequency doubling during direction mode.
Thanks to the extreme low current consumption the
U2044B can be connected to the battery directly.

 Very low susceptibility to EMI
 Protection according to ISO/TR7637/1 level 4
 Extremly low current consumption < 10 A

(@switches open)

 Reverse polarity protection

 Minimum lamp load for flasher operation: 1 W

 Three control inputs: left, right and hazard warning

Ordering Information

Extended Type Number Package Remarks

U2044B DIP14

U2044B-FP SO14

Pin Description

Pin Symbol Function

1 OSC Oscillator
2 SIL Start input left
3 SIR Start input right
4 SIHW Start input hazard warning
5 V

V

S

S

6 CR1 Control input relay 1
7 CR2 Control input relay 2
8 LD Lamp failure detection
9 V

V

S

S

10 GND IC ground
11 OR1 Output relay 1
12 V

V

S

S

13 OR2 Output relay 2
14 OSC Oscillator

OSC

SIL

SIR

SIHW

V

CR1

CR2

1

2

3

4

U2044B

S

5

6

7

Figure 1. Pinning

10

14

13

12

11

OSC

OR2

Vs

OR1

GND

9

V

S

LD

8

12750

Rev. A4, 03-Apr-01 1 (6)

U2044B

Block Diagram

C

4.7 F

R

1

82 k

9
5

R

VS–81 mV

V

Ref1

+

–

V

Ref2

R

3

4.7 k

R

4

6

4.7 k

8

R

R

10

1.2 k

9

47 k

R

8

47 k

6

7

/2

V

S

12

right

K1

4.7 k

+

–

+

–

–

+

–

+

R

1

14

1

VS–6 V

+

–

Relay
12

27.5 V

GND 101311 3 2 4

R

2

220 

Hazard warning

Shunt

30 m

Contact

12

30

30

30

15

1.2 k

Figure 2. Application circuit

R

for protection against continous reversed polarity: 1 W att

2

Functional Description

Pin 1 and Pin 14, Oscillator

Flashing frequency, f1, is determined by the R1C
components as follows (see figure 2):

f



1

R1 C1 1.5

where C1  47 F

In the case of a lamp outage, the oscillator frequency is
switched to the lamp outage frequency f2 with

f2  2.2  f1.

Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode (bright phase): 40%

1

Hz

R1  6.8 k to 180 k

R

R

5

7

1.2 k

left

Pin 2 and Pin 3, Start input right and left
Flashing is disabled as long as the input comparator is tied

1

to GND (pull-down resistor R7 or R5). The high-side
flasher switch ”left” or ”right” changes the comparator
status and enables the output stage at Pin 11 or Pin 13. R
and R4 are protection resistors for the input stage.

With an open flasher switch the current consumption is
only I  10 A. The IC is kept in stand-by mode until
there is a voltage drop of V  6.9 V at the pull-down re­sistor.

Direction mode can only be activated when the ignition
switch is in ON-position as shown in figure 2.

31

12700

6

Rev. A4, 03-Apr-012 (6)