Bypass Diode for LTC4366-2 Surge Stopper

I am using the LTC4366-2 surge stopper in a MIL-STD-1275 application, and have added Rs to mitigate output short circuits. In simulation, I have modelled the circuit both with and without Dbypass and cannot determine what role it is playing in the circuit. It appears that the bulk of the gate capacitance is charged via the gate pin of the LTC4366-2, rather the through the bypass diode and the external gate capacitor. What purpose does it serve? The datasheet indicates that it is designed to sink the current from the MOSFET gate capacitor during these events, but the simulations are showing ~25mA going into the GATE pin and ~5mA through the diode and into the external gate capacitor.

How much current is the GATE pin able to sink during an overvoltage event? It appears that it is able to sink somewhere between 200mA and 300mA.

  • +1
    •  Analog Employees 
    on Jan 7, 2021 12:23 AM

    Rs is a current limiting resistor to prevent the internal clamp from being damaged when CG is discharged.

    The diode-cap path prevents the FET from “self-enhancing” when there is a transient on the input. Charge that would normally couple through the FET’s parasitic capacitance and build up on the gate are instead shorted to ground.

    During an overvoltage event, the gate pin sinks: 122mA (min), 200mA (typ), 300mA (max)