I am using Cree mosfet model (from CREE website, PLECS thermal model of mosfet). Do i need to define on-Resistance Ron in this case, I assume it should take that value from mosfet model as Ron changes with temperature.
Hello,
No, this is not required. The thermal data provided by Wolfspeed (Cree) is temperature-dependent, so the losses will vary depending on temperature. The on-resistance parameter is simply to provide a fixed Ron to the electrical simulation, which runs in parallel to the thermal loss calculation. The impedance of the device could be important if you have parallel devices (such as including an external Schottky diode) and want to ensure proper current sharing between the two devices for accurate loss calculations of both.
Kris