We are planning to use LT4320-1 for a 400 Hz three phase AC input to 28V DC output, 11 kW Ideal Rectification application. At full load the current going through MOSFET will be around 430A. The design will be based on DC2465A Demo card schematic with new selected high power/current MOSFET. Due to the huge gating power demand of selected high power MOSFET and limited LT4320-1 driving capability we are planning to add one layer buffer (MOSFET driver) between LT4320-1 and MOSFET (see below diagram). With this MOSFET driver in between, the design will lost top MOSFET Vdson regulation capability. The top MOSFET will be either fully on or off. The Rdson of the selected MOSFET is 0.15 mohm. At full load (430 A) the Vdson will be around 65 mV which is higher than top MOSFET Vds regulation rang so gating voltage for the top MOSFET from LT4320-1 will be fully on. So at full load there will be no impact on the ideal rectifier operation. Our concern is at light load (low current) when Vdson is lower than the regulation level (26 mV to 55 mV) if top MOSFET is fully on. How low the gating voltage from LT4320-1 will be for top MOSFET if top MOSFET Vdson is lower than the regulation level (26 mV to 55 mV)? If the gating voltage will drop close to 0V then the MOSFET could work on jittering mode (switching between on and off). Is there a way we can fake the top MOSFET regulation, for example by adding a Diode or resistor between Vout+ and LT4320-1 OUTP (pin 6) to make LT4320-1 detected Vdson is always higher than regulation level even when actual Vdson is lower than 26 mV?
Your help will be highly appreciated,