5

4721C–AUTO–02/08

U2044B

3.6

Lamp Outage Detection (Pin 8)

The lamp current is monitored via an external shunt resistor, R

K1, with its reference voltage of typically 81 mV (V

lamps is detected according to the following calculation:

Nominal current of 1 lamp: 21W/(V

I

Nominal current of 2 lamps: 2

× 21W/(V

I

We recommend setting the detection threshold in the middle of the current range: I

2.7A

Thus the shunt resistor is calculated as:

R

R

Comparator K1’s reference voltage is matched to the characteristics of filament lamps (see sec-

tion “Control Signal Threshold”).

The combination of the shunt resistor and the resistance of the wire harness prevents pin 8 from

a too high voltage in the case of shorted lamps.

3.7

Supply Voltage (Pin 9)

This pin supplies the oscillator, the comparators and the logic parts of the IC.

3.8

GND (Pin 10)

The integrated circuit is protected against transients according to ISO-TR 7637-3 level 3 via

resistor R

R

battery.

3.9

Control Output Relay 1 and 2 (Pin 11 and 13)

The relay control outputs are high-side drivers with a low saturation voltage and capable of driv-

ing a typical automotive relay with a coil resistance of 60

Ω.

3.10

Supply Voltage Power (Pin 12)

This pin supplies the relay drivers connected directly to the battery (Kl 30). It is internally

clamped by a 27-V Z-diode.