Hello,
I was comparing different GaN FETs, specifically ones with very low Coss and higher Rdson. But looking at the max current ratings (both continuous and pulsed) has me very confused.
My assumption for the continuous max current was that it’s based purely on temperature rise. Therefore, all the devices in the same package would have similar power dissipation at their rated max continuous current (Rdson*Idcont^2).
For the pulsed current rating, I saw this topic where it was stated that this rating is related to saturation of the FET. Therefore I would expect all devices to happen at a similar Vds = Rdson*Idpulse.
But when comparing different devices, neither of these expectations hold. Below I’ve tabulated several devices in the BGA 0.9x0.9 or LGA 2.05x0.85 packages.
The strangest observation is that Id cont seems to be mostly independent of Rdson, even within the same package. For example, EPC2035 has 10x lower Rdson compared to EPC2037, but their rated Id cont is equal, even though their power dissipation would be different by a factor of x10. This suggests there’s some limit on continuous Id besides temperature.
And the Vds corresponding to the pulsed Id varies by over a factor of two between devices. Maybe if I measured Vds with a spice model of each FET, I would get more consistent results?
These discrepancies occur whether I use the typical or maximum Rdson in the calculations.
Just hoping to get a proper understanding of what these specifications mean and how to apply them.
Regards,
Mike