ISO5851: Negative or Zero Vin to switch the mosfet?

Hi Fax,

We would recommend to have both Miller clamp function and negative power supply for applications where power FETs are switched at high frequency, and there are high gate voltage ringing.

With Regards,

Xiong

Hello Xiong,

Thanks for reply. What do you mean by high frequency and high gate voltage? Do you have some f and V range I can still use 0V to switch off mosfets?

Thanks,
FAX

Hi Fax,

The negative voltage is used to clamp the FET to be OFF state when the PWM signal is LOW, and to prevent the FET from falsely turned on because of Miller capacitance. Negative voltage is recommended when the gate voltage rining is high, which usually occurs when the FET is switched at high frequency with high dv/dt slew rate. The voltage ringing also depends on the PCB board design. So it is hard to simply put a range of voltage and frequency. In general, we recommend customer to use negative power supply for SiC based applications.

With Regards,
Xiong