U2044B Datasheet, PDF (4/8 Pages) TEMIC Semiconductors – Dual Output Flasher

Functional Description
Oscillator (Pin 1 and 14) Flashing frequency, f₁, is determined by the R₁C₁ components as follows (see Figure 1):
f₁ » _R-----₁----_´-----_C---¹--₁----_´-----₁---_.--₅- Hz
where C₁ £ 47 µF
R₁ = 6.8 kW to 180 kW
In the case of a lamp outage, the oscillator frequency is switched to the lamp outage fre-
quency f₂ with f₂ » 2.2 ´ f₁.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode:
40% (bright phase)
Start Input Right and Left
(Pin 2 and 3)
Flashing is disabled as long as the input comparator is tied to GND (pull-down resistor
R₇ or R₅). The high-side flasher switch left or right changes the comparator status and
enables the output stage at pin 11 or Pin 13. R₆ and R₄ are protection resistors for the
input stage.
With an open flasher switch the current consumption is only I < 10 µA. The IC is kept in
stand-by mode until there is a voltage drop of V » 6.9 V at the pull-down resistor.
Direction mode can only be activated when the ignition switch is in the ON-position as
shown in Figure 1.
Start Input Hazard
Warning (Pin 4)
In contrast to the direction switches, the hazard input is a low-side type. The pull-up
resistor R₁₀ provides the off-state. R₃ is a protection resistor for the input stage. Hazard
warning can be activated independent of the ignition switch position.
Supply Voltage Sense
(Pin 5)
This pin supplies the lamp outage comparator at pin 8 and is externally connected to the
battery (Kl 30).
Control Input Relay 1
and 2 (Pin 6 and 7)
The feedback detects the bright phase and the dark phase and enables the oscillator.
Lamp Outage Detection
(Pin 8)
The lamp current is monitored via an external shunt resistor, R_Shunt and an internal com-
parator, K1, with its reference voltage of typically 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):
Nominal current of 2 lamps: 2 ´ 21 W / (V_S = 12 V):
I_lamp = 1.75 A
I_lamp = 3.5 A
We recommend setting the detection threshhold in the middle of the current range:
I_outage » 2.7 A
Thus the shunt resistor is calculated as:
R_Shunt = V_T (K1)/I_outage
R_Shunt = 81 mV/2.7 A = 30 mW
Comparator K1's reference voltage is matched to the characteristics of filament lamps
(see section “Control Signal Threshold”).
4 U2044B
4721A–AUTO–05/03