ATA6661_08 Datasheet, PDF (4/9 Pages) ATMEL Corporation – LIN Transceiver

4. Functional Description
4.1 Pin 1, GND
The U643B is protected against damage in case of battery reversal via resistor R₄ to ground
(–31). An integrated protection circuit together with external resistances R₂ and R₄ limits the cur-
rent pulses in the IC.
4.2 Pin 2, Supply Voltage, V_S Power
The arrangement of the supply connections to pin 2 must be so as to ensure that on the connec-
tion printed circuit board (PCB), the resistance of V_S to pin 6 is lower than that to pin 2.
4.3 Pin 3, Relay Control Output (Driver)
The relay control output is a high-side driver with a low saturation voltage. It is capable of driving
a typical automotive relay with a minimum coil resistance of 60Ω.
4.4 Pin 4 and 5, Oscillator
The flashing frequency, f₁, is determined by the R₁C₁ components as given by the formula below
(see Figure 2-1 on page 2):
f₁ ≈
-----------------¹-------------------
R₁ × C₁ × 1.5
Hz
where C₁ ≤47 µF, R₁ = 6.8 kΩ to 510 kΩ
In case of a lamp outage (see pin 7) 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)
4.5 Pin 6, Supply Voltage, Sense
For accurate monitoring via the shunt resistor, a minimized layer resistance from point V_S/shunt
to pin 6 is recommended.
4 U643B
4727B–AUTO–09/05