U2043B
Pin Description
Pin
1
2
3
4
5
6
7
8
Symbol
GND
V
S
REL
OSC
OSC
V
S
LD
SI
Function
IC ground
Supply voltage V
S
Relay driver
C
1
oscillator
R
1
oscillator
Supply voltage V
S
Lamp failure detection
Start input (49a)
GND
Vs
REL
OSC
1
2
8
7
SI
LD
Vs
OSC
12749
U2043B
3
4
6
5
Figure 2. Pinning
Functional Description
Pin 1,
GND
The integrated circuit is protected against damage via
resistor R
4
to ground (–31) in the case of battery reversal.
An integrated protection circuit together with external
resistances R
2
and R
4
limits the current pulses in the IC.
Pin 2,
Supply voltage, V
S
- 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 V
S
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-
tive relay with a minimum coil resistance of 60
W
.
Pin 4 and 5
Oscillator
Flashing frequency, f
1
, is determined by the R
1
C
1
compo-
nents as follows (see figure 1):
mized layer resistance from point V
S
/ shunt to Pin 6 is
recommended.
Pin 7,
Lamp outage detection
The lamp current is monitored via an external shunt
resistor R
3
and an internal comparator K1 with its
reference voltage of typ. 81 mV (V
S
= 12 V). The outage
of one lamp out of two lamps is detected according to the
following calculation:
Nominal current of 1 lamp: 21 W / (V
S
= 12 V):
I
lamp
= 1.75 A
Nominal current of 2 lamps: 2 x 21 W / (V
S
= 12 V):
I
lamp
= 3.5 A.
The detection threshold is recommended to be set in the
middle of the current range: I
outage
2.7 A
Thus the shunt resistor is calculated as:
R
3
= V
T
(K1) / I
outage
R
3
= 81 mV/2.7 A = 30 m
W
.
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.
[
where
[
R C1 1.5 Hz
C
47
m
F
R
+
6.8 k
W
to 510 k
W
f
1
1
1
1
1
In the case of a lamp outage (see Pin 7) the oscillator
frequency is switched to the lamp outage frequency f
2
with f
2
2.2 f
1
.
[
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-
Pin 8,
Start input
Start condition for flashing: the voltage at Pin 8 has to be
below less than V
S
– 5 V (flasher switch closed).
Humidity and dirt may decrease the resistance between
49 a and GND. If this leakage resistance is 5 k
W
the IC
is still kept in its off-condition. In this case the voltage at
Pin 8 is greater than V
S
– 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.
u
2 (6)
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97
TEMIC [ TEMIC SEMICONDUCTORS ]
