I am currently evaluating several power MOSFET’s looking at their switch on and off times.
My testing has employed a few different gate drivers, however the bulk of my testing is with the ST Micro L6491 gate driver IC.
The MOSFET I am hoping to proceed with in my project is the Nexperia PSMNR90-40SSH.
Referencing Vishay document AN608A and the following parameters from the PSMNR90-40SSH datasheet, I calculated the following as the turn on and turn off times.
Having set up a test circuit using a 24 Ohm gate resistor, the following are the scope images for the total turn on and turn off of this MOSFET. These measurements assume turn on is 10% Vgs to 10% Vds, and turn off is 90% Vgs to 90% Vds. The load in the test circuit is a 3 Ohm thick film resistor.
Turn-on = 452ns Turn-off = 636ns
I have made about a dozen sets of measurements using various gate resistor values and with three other MOSFETs; all of my measurements are values that far exceed the calculated estimates.
I did find a SPICE model for the PSMNR90-40SSH and modeled the test circuit in NI Multisim. The measurements for turn on and turn off were:
Turn on = 180ns Turn off = 438ns
How do I account for the discrepancy between calculated times and measured values? How are other people estimating accurate switching times? Are there any considerations I should be making that I may have overseen?