1 GND IC ground
2 VS Supply voltage VS
3 REL Relay driver
4 OSC C1 oscillator
5 OSC R1 oscillator
6 VS Supply voltage VS
7 LD Lamp failure detection
8 SI Start input (49a)
Figure 2. Pinning
Pin 1, GND
The integrated circuit is protected against damage via
resistor R4 to ground (–31) in the case of battery reversal.
An integrated protection circuit together with external
resistances R2 and R4 limits the current pulses in the IC.
Pin 2, Supply voltage, VS - Power
The arrangement of the supply connections to Pin 2 must
be such as ensure that, on the connection printed circuit
board (PCB), the resistance of VS to Pin 6 is lower than
that to Pin 2.
Pin 3, Relay control output (driver)
The relay control output is a high-side driver with a low
saturation voltage and capable to drive a typical automo-
Wtive relay with a minimum coil resistance of 60 .
Pin 4 and 5 Oscillator
Flashing frequency, f1, is determined by the R1C1 compo-
nents as follows (see figure 1):
6.8 kW to 510 kW
In the case of a lamp outage (see Pin 7) 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: 40% (bright phase)
Pin 6, Supply voltage, Sense
For accurate monitoring via the shunt resistor, a mini-
mized layer resistance from point VS / shunt to Pin 6 is
Pin 7, Lamp outage detection
The lamp current is monitored via an external shunt
resistor R3 and an internal comparator K1 with its
reference voltage of typ. 81 mV (VS = 12 V). The outage
of one lamp out of two lamps is detected according to the
Nominal current of 1 lamp: 21 W / (VS = 12 V):
Ilamp = 1.75 A
Nominal current of 2 lamps: 2 x 21 W / (VS = 12 V):
Ilamp = 3.5 A.
[The detection threshold is recommended to be set in the
middle of the current range: Ioutage 2.7 A
Thus the shunt resistor is calculated as:
WR3 = VT (K1) / Ioutage
R3 = 81 mV/2.7 A = 30 m .
Comparator K1‘s reference voltage is matched to the
characteristics of filament lamps (see “control signal
threshold” in the data part).
The combination of shunt resistor and resistance of wire
harness prevents Pin 7 from a too high voltage in the case
of shortet lamps.
Pin 8, Start input
Start condition for flashing: the voltage at Pin 8 has to be
below less than VS – 5 V (flasher switch closed).
u WHumidity and dirt may decrease the resistance between
49 a and GND. If this leakage resistance is 5 k the IC
is still kept in its off-condition. In this case the voltage at
Pin 8 is greater than VS – 5 V.
During the bright phase the voltage at Pin 8 is above the
K2 threshold, during the dark phase it is below the K3
threshold. For proper start conditions a minimum lamp
wattage of 10 W is required.
2 (6) TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97