U6043B Datasheet, PDF (4/9 Pages) ATMEL Corporation – FLASHER IC WITH 19-M SHUNT

Functional Description
Pin 1, GND
Pin 2, Supply Voltage,
V_S power
Pin 3, Relay Control
Output (Driver)
The U6043B 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 current pulses in the IC.
The arrangement of the supply connections to Pin 2 (and 6) must be so as to ensure
that on the connection printed circuit board (PCB), the resistance of V_S to Pin 6 is lower
than that to Pin 2.
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 60 W.
Pin 4 and 5, Oscillator
Pin 6, Supply Voltage,
Sense
Pin 7, Lamp Outage
Detection
The flashing frequency, f₁, is determined by the R₁C₁ components as given by the fol-
lowing formula below (see Figure 1):
f₁ » _R-----₁----_´-----_C---¹--₁----_´----₁----_.-₅-- Hz
where C₁ £ 47 µF, R₁ = 6.8 kW to 510 kW
In case of a lamp outage (see Pin 7) the oscillator frequency is switched to the lamp out-
age frequency f₂ with f₂ » 2.2 ´ f₁.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode: 40% (bright phase)
For accurate monitoring via the shunt resistor, a minimized layer resistance from point
V_S/shunt to Pin 6 is recommended.
The lamp current is monitored via an external shunt resistor R_sh and an internal compar-
ator K1 with its reference voltage of typ. 49 mV (V_S = 12 V). The outage of one lamp is
detected according to the following calculation:
Nominal current of 1 lamp: 21 W/(V_S = 12 V): I_lamp = 1.75 A
Nominal current of 2 lamps: 2 ´ 21 W/(V_S = 12 V): I_lamp = 3.5 A
We recommend setting the detection threshold in the middle of the current range:
I_outage » 2.7 A
Thus, the shunt resistor is calculated as:
R_sh = V_T (K1)/I_outage
R_sh = 49 mV/2.7 A = 18 mW
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 case of shorted lamps.
4 U6043B
4726A–AUTO–06/03