U2043B Datasheet, PDF (2/6 Pages) TEMIC Semiconductors – Flasher, 30-mohm Shunt, Pilot Lamp to GND or V Batt

U2043B
Pin Description
Pin Symbol
Function
1
GND IC ground
2
V_S Supply voltage V_S
3
REL Relay driver
4
OSC C₁ oscillator
5
OSC R₁ oscillator
6
V_S Supply voltage V_S
7
LD Lamp failure detection
8
SI Start input (49a)
GND 1
8 SI
Vs ²
REL ₃
7 _LD
U2043B
6 _Vs
OSC ₄
5 OSC
12749
Figure 2. Pinning
Functional Description
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, 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
W ^{saturation voltage and capable to drive a typical automo-}
tive 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):
where
[f₁
R₁
1
C₁
1.5 ^Hz
 C₁
+ R₁
47 mF
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 V_S / shunt to Pin 6 is
recommended.
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 (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:
W ^{R3 = 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 V_S – 5 V (flasher switch closed).
u W ^{Humidity 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 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.
2 (6)
TELEFUNKEN Semiconductors
Rev. A2, 25-Feb-97