U6084B_05 Datasheet, PDF (6/11 Pages) ATMEL Corporation – PWM Power Control with Automatic Duty-cycle Reduction

3.11 Pin 16 – Supply Voltage, V_s or V_Batt
3.11.1
Undervoltage Detection
In the event of voltages of approximately V_Batt < 5.0V, the external FET is switched off and the
latch for short-circuit detection is reset.
A hysteresis ensures that the FET is switched on again at approximately V_Batt ≥ 5.4V.
3.11.2
Overvoltage Detection
• Stage 1
– If overvoltages of V_Batt > 20V (typically) occur, the external transistor is switched off
and switched on again at V_Batt < 18.5V (hysteresis).
• Stage 2
– If V_Batt > 28.5V (typically), the voltage limitation of the IC is reduced from 26V to 20V.
The gate of the external transistor remains at the potential of the IC ground, thus
producing voltage sharing between the FET and lamps in the event of overvoltage
pulses (for example, load dump). The short-circuit protection is not in operation. At
V_Batt < 23V, the overvoltage detection stage 2 is switched off.
6 U6084B
4677C–AUTO–09/05