ATMEL U2043B User Manual
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U2043B
Flasher, 30-m Shunt, Pilot Lamp to GND or V
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
Features
Temperature and voltage compensated frequency
Warning indication of lamp failure by means of
frequency doubling
Minimum lamp load for flasher operation 10 W
Block Diagram
6
C
1
4
Measuring comparator
V6–81 mV
K
1
2
hazard mode as well as direction mode. The pilot lamp
can be connected either to V
Batt
Relay output with high current carrying capacity and
low saturation voltage
Low susceptibility to EMI
R
Shunt
7
Batt
or GND.
3
30 m
+ V
+ 49
S
3
Relay
R
8
1
2
3.3 k
R
1
100
GND
– 31
5
13283
Pulse
generator
3.8 k
K
V6–5 V
3
49 a–Comparator
23 V
IC Ground
Figure 1. Block diagram
R
1
Ordering Information
Extended Type Number Package Remarks
U2043B DIP8
U2043B–FP SO8
Pilot lamp 5 W
49 a
21 W 21 W 5 W21 W21 W5 W
Indicator lamps
Pilot lamps
Rev. A4, 02-Apr-01 1 (6)
U2043B
Pin Description
Pin Symbol Function
1 GND IC ground
2 V
Supply voltage V
S
S
3 REL Relay driver
4 OSC C1 oscillator
5 OSC R1 oscillator
6 V
Supply voltage V
S
S
7 LD Lamp failure detection
8 SI Start input (49a)
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 R
Pin 2, Supply voltage, V
The arrangement of the supply connections to Pin 2 must
be so as to ensure that, on the connection printed circuit
board (PCB), the resistance of VS 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 automotive relay with a minimum coil resistance of 60 .
Pin 4 and 5 Oscillator
Flashing frequency, f1, is determined by the R1C1 components as follows (see figure 1):
f
where C1 47 F
R1 6.8 k to 510 k
In the case of a lamp outage (see Pin 7) the oscillator
frequency is switched to the lamp outage frequency f
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 minimized layer resistance from point V
recommended.
limits the current pulses in the IC.
4
- Power
S
1
1
R1 C1 1.5
Hz
/ shunt to Pin 6 is
S
GND
Vs
1
2
8
SI
7
LD
U2043B
REL
OSC
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
of one lamp out of two lamps is detected according to the
following calculation:
Nominal current of 1 lamp: 21 W / (V
I
= 1.75 A
lamp
Nominal current of 2 lamps: 2 x 21 W / (V
I
= 3.5 A.
lamp
The detection threshold is recommended to be set in the
middle of the current range: I
Thus the shunt resistor is calculated as:
R
= V
(K1) / I
3
T
R
= 81 mV/2.7 A = 30 m.
3
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 shorted lamps.
Pin 8, Start input
Start condition for flashing: the voltage at Pin 8 has to be
less than VS – 5 V (flasher switch closed).
Humidity and dirt may decrease the resistance between
49 a and GND. If this leakage resistance is 5 k the IC
2
is still kept in its off-condition. In this case the voltage at
Pin 8 is greater than VS – 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.
3
4
Figure 2. Pinning
outage
6
Vs
OSC
5
= 12 V). The outage
S
= 12 V):
S
2.7 A
outage
= 12 V):
S
12749
Rev. A4, 02-Apr-012 (6)
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