I've been working on a digitally controlled synchronous buck converter that uses a driver chip to drive a high side and low side N-FET. It works as expected, but I'm now tweaking the design to maximize efficiency and am having a hard time choosing an optimum FET for the job. If I understand correctly, the two major parameters I should be looking at are turn-on/off times and Rds(on), both of which I want to be low, correct?
My converter switches at 100kHz and the FETs I'm using now have a turn-on/off delay time of 2.1 and 13.1 ns, respectively and an Rds(on) of 65 mΩ. I can find FETs with lower Rds(on) but they are typically a little slower (25/40ns on/off for example), but still suggested for DC-DC switching applications.
So, my question is: what is more important? Faster switching or lower Rds(on). My aim is maximum efficiency.
My converter switches at 100kHz and the FETs I'm using now have a turn-on/off delay time of 2.1 and 13.1 ns, respectively and an Rds(on) of 65 mΩ. I can find FETs with lower Rds(on) but they are typically a little slower (25/40ns on/off for example), but still suggested for DC-DC switching applications.
So, my question is: what is more important? Faster switching or lower Rds(on). My aim is maximum efficiency.