LT4363 Gate capacitor reference

On input transients in which i do not want to clamp the output voltage or trip an over current event, I am finding that the charge pump output greatly lags the jump in input voltage.  This causes high loss on the pass FET during the the event.  If I reference the gate capacitor to the source of the FET this issue disappears.  Is it valid to attach the external cap between gate and ground?

Parents
  • 0
    •  Analog Employees 
    on Apr 2, 2021 11:47 PM

    I assume you meant "between gate and source". You can but then it only helps prevent MOSFET self-enhancement (gate step up above threshold) and consequent inrush current spike during a fast input step up from 0V. If that is not a concern or application condition and since LT4363 does not require a gate capacitor for loop stability, you might as well remove the capacitor since a gate-source capacitor doesn't help to lower startup inrush. Refer datasheet page 15 for further details.

Reply
  • 0
    •  Analog Employees 
    on Apr 2, 2021 11:47 PM

    I assume you meant "between gate and source". You can but then it only helps prevent MOSFET self-enhancement (gate step up above threshold) and consequent inrush current spike during a fast input step up from 0V. If that is not a concern or application condition and since LT4363 does not require a gate capacitor for loop stability, you might as well remove the capacitor since a gate-source capacitor doesn't help to lower startup inrush. Refer datasheet page 15 for further details.

Children