U2043B
3. Functional Description
3.1
GND (Pin 1)
The integrated circuit is protected against damage via resistor R
4
to ground (–31) in the case of
battery reversal. An integrated protection circuit together with external resistances R
2
and R
4
limits the current pulses in the IC.
3.2
Supply Voltage, V
S
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 V
S
to pin 6 is lower than that to pin 2.
3.3
Relay 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 60Ω.
3.4
Oscillator (Pin 4 and 5)
Flashing frequency, f
1
, is determined by the R
1
C
1
components as follows (see
Figure 1-1 on
page 1):
1
-
f
1
= ------------------------------------
Hz
R
1
×
C
1
×
1.5
where
C
1
≤
47 µF
R
1
= 6.8 kΩ to 510 kΩ
In the case of a lamp outage (see pin 7) the oscillator frequency is switched to the lamp outage
frequency f
2
with f
2
≈
2.2
×
f
1
.
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 V
S
/shunt
to pin 6 is recommended.
3
4720B–AUTO–09/05
ATMEL [ ATMEL CORPORATION ]
