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Features
Temperature and Voltage Compensated Frequency
Warning Indication of Lamp Failure by Means of Frequency Doubling
Minimum Lamp Load for Flasher Operation 10W
Relay Output with High Current Carrying Capacity and Low Saturation
Voltage
Low Susceptibility to EMI
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1. Description
The integrated circuit U2043B is used in relay-controlled automotive flashers where a
high EMC level is required. A lamp outage is indicated by frequency doubling during
hazard mode as well as direction mode. The pilot lamp can be connected either to
VBatt or GND.
Figure 1-1. Block Diagram
C1
4
6
Measuring comparator
K 1 V 6-81 mV
2
7
R3 30 m
Shunt
+VS
+ 49
Pilot lamp 5 W
Pulse
R1 generator
3.8 k
K 3 V 6-5 V
5
49 a-Comparator
23 V
IC Ground
3
Relay
8 R2
3.3 k
1 R1
100
GND
- 31
49 a
5 W 21 W 21 W
21 W 21 W 5 W
Indicator lamps
Pilot lamps
Flasher, 30 m
Shunt, Pilot
Lamp to GND or
VBatt
U2043B
Rev. 4720B–AUTO–09/05

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2. Pin Configuration
Figure 2-1. Pinning DIP8/SO8
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GND 1
8 SI
VS 2
REL 3
U2043B
7 LD
6 VS
OSC 4
5 OSC
Table 2-1.
Pin
1
2
3
4
5
6
7
8
Pin Description
Symbol
GND
VS
REL
OSC
OSC
VS
LD
SI
Function
IC ground
Supply voltage VS
Relay driver
C1 Oscillator
R1 Oscillator
Supply voltage VS
Lamp failure detection
Start input (49a)
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U2043B
3. Functional Description
3.1 GND (Pin 1)
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.
3.2 Supply Voltage, VS Power (Pin 2)
The arrangement of the supply connections to pin 2 must be so as to ensure that, on the con-
nection printed circuit board (PCB), the resistance of VS to pin 6 is lower than that to pin 2.
www.Da3ta.S3heet4UR.ceolmay Control Output (Driver, Pin 3)
The relay control output is a high-side driver with a low saturation voltage and capable of driving
a typical automotive relay with a minimum coil resistance of 60.
3.4 Oscillator (Pin 4 and 5)
Flashing frequency, f1, is determined by the R1C1 components as follows (see Figure 1-1 on
page 1):
f1
=
------------------1------------------
R1 × C1 × 1.5
Hz
where
C1 47 µF
R1 = 6.8 kto 510 k
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:
Duty cycle in lamp outage mode:
50%
40% (bright phase)
3.5 Supply Voltage, Sense (Pin 6)
For accurate monitoring via the shunt resistor, a minimized layer resistance from point VS/shunt
to pin 6 is recommended.
4720B–AUTO–09/05
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3.6 Lamp Outage Detection (Pin 7)
The lamp current is monitored via an external shunt resistor R3 and an internal comparator K1
with its reference voltage of typically 81 mV (VS = 12V). The outage of one lamp out of two
lamps is detected according to the following calculation:
Nominal current of 1 lamp: 21W/(VS = 12V):
Ilamp = 1.75A
Nominal current of 2 lamps: 2 × 21W/(VS = 12V): Ilamp = 3.5A
We recommend setting the detection threshold in the middle of the current range:
Ioutage 2.7A
Thus, the shunt resistor is calculated as:
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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 sec-
tion “Control Signal Threshold”).
The combination of the shunt resistor and the resistance of the wire harness prevents pin 7 from
a too high voltage in the case of shorted lamps.
3.7 Start Input (Pin 8)
Start condition for flashing:
The voltage at pin 8 has to be less than VS – 5V (flasher switch closed).
Humidity and dirt may decrease the resistance between 49a and GND. If this leakage resistance
is > 5 kthe IC is still kept in its off-condition. In this case the voltage at pin 8 is greater than
VS – 5V.
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 10W is required.
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U2043B
4. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Reference point: pin 1
Parameters
Symbol
Value
Unit
Supply voltage, pins 2 and pin 6
Surge forward current
tp = 0.1 ms
tp = 2 ms
tp = 2 ms
www.DataOSuhtepeut4t Ucu.croremnt, pin 3
Power Dissipation
VS
IFSM
IFSM
IFSM
IO
16.5
1.5
1.0
50
0.3
V
A
A
mA
A
Tamb = 95°C, DIP8
SO8
Tamb = 60°C, DIP8
SO8
Junction temperature
Ambient temperature range
Storage temperature range
Ptot
Ptot
Ptot
Ptot
Tj
Tamb
Tstg
420
340
690
560
150
–40 to +95
–55 to +150
mW
mW
mW
mW
°C
°C
°C
5. Thermal Resistance
Parameters
Junction ambient, DIP8
Junction ambient, SO8
Symbol
RthJA
RthJA
Value
110
160
Unit
K/W
K/W
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