The on chip zener diode stack is utilised as an active clamp arrangement that activates the gate in order to clamp the drain-source voltage at typically 65V. When a self protected MOSFET detects the presence of a voltage above 65V, the active clamp allows the entire power MOSFET area to turn on irrespective of the input levels and uniformly share the energy imposed within the device during the over-voltage event to absorb the ring-off energy from an inductive load, or power supply transient fed through the load.

