FM2044 Shanghai Fudan Microelectronics Co., Ltd., FM2044 Datasheet - Page 5

• Manufacturer Part Number: FM2044
• Description: Dual Output Flasher
• Manufacturer: Shanghai Fudan Microelectronics Co., Ltd.

Function Description
Oscillator (Pin 1 and 14)
Flashing frequency, f
components as follows (see Figure 1):
Where C
In the case of a lamp outage, the oscillator
frequency is switched to the lamp outage frequency
f
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 R
high-side flasher switch left or right changes the
comparator status and enables the output stage at
pin 11 or Pin 13. R
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 R
provides the off-state. R
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.
FM2044 Dual Output Flasher
f
2
1
with f
≈
R
1
×
2
R
C
≈ 2.2 x f
1
1
1
1 =
≤ 47µF
×
1.5
6.8KΩ ~ 180KΩ
Hz
1
.
6
and R
1
, is determined by the R
3
is a protection resistor for
4
are protection resistors
7
or R
5
). The
1
C
10
1
Lamp Outage Detection (Pin 8)
The lamp current is monitored via an external shunt
resistor, R
its reference voltage of typically 81 mV (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
Nominal current of 2 lamps:
2 x 21 W / (V
We recommend setting the detection threshold in
the middle of the current range: I
Thus the shunt resistor is calculated as:
R
R
Comparator K1's reference voltage is matched to
the characteristics of filament lamps.
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.
Supply Voltage (Pin 9)
This pin supplies the oscillator, the comparators and
the logic parts of the IC.
GND (Pin 10)
The integrated circuit is protected against transients
according to ISO-TR 7637-3 level 3 via resistor R
to ground (-31). An integrated protection circuit
together with external resistors R
and R
also protected against reversed battery.
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 driving a typical
automotive relay with a coil resistance of 60 Ω.
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.
Shunt
Shunt
Ver 1.1
= V
= 81 mV/2.7 A = 30 mΩ
9
limits the current pulses in the IC. The IC is
S
T
= 12 V): I
Shunt
(K1)/I
S
= 12 V): I
and an internal comparator, K
outage
lamp
= 1.75 A
lamp
= 3.5 A
outage
2
, R
≈ 2.7 A
Specification
3
, R
S
4
, R
= 12 V).
1
, with
6
, R
5
2
8