U644B

TELEFUNKEN Semiconductors

Rev. A2, 25-Feb-97

1 (6)

Flasher, 18-m

W Shunt, Extremly Low Current Consumption

Description

The bipolar integrated circuit, U644B, is used in relay-

controlled automotive flashers where a high level EMC

is required. Lamp outage is indicated by frequency doub-

ling during hazard warning as well as direction mode.

If the flasher module provides an 4-pin connector the

control pin of U644B (Pin 6) can be used to operate the

IC in an extremly low-current mode.

Features

D Frequency doubling indicates lamp outage

D Frequency independent of temperature and voltage

change

D Relay driver output with high current-carrying

capacity and low saturation voltage

D Minimum lamp load for flasher operation: 1 W

D Very low susceptibility to EMI

D Protection according to ISO TR7637/1 level 4

D Control input (Kl 15)

Ordering Information

Extended Type Number

Package

Remarks

U644B

DIP8

U644B-FP

SO8

Block Diagram

V

S

–49 mV

Pulse

generator

GND

20 k

W

3.3 k

W

Relay

7

15

49 a

4

5

K

2

K

1

K

3

C

1

R

1

2

12707

R

3

49 a

Comparator K

2

49 a

Comparator K

3

2 k

W

20 k

W

20 k

W

20 k

W

13 k

W

30 V

6

3

8

1

Shunt

R

4

GND

–31

R

5

10 k

W

30

18 m

W

Measuring

comparator K

1

220

W

R

2

Figure 1. Application circuit as a car flasher with control input