Sizing of MOSFET IN BOOST Converter

[Abhilash_001]

I am designing a dc dc boost converter and i wanted to size my mosfet based on Ron value i wanted to know to plot this like i know Ron = (vin-vo)/i but how to plot this in cadence and calculate while using trans anyalsis

 

[Easy peasy]

Ooh - I know this one - it has to be big enough so as not to get too hot.

Watts = Irms^2 x Ron ( at 80 deg C ) + switching losses, has to be balanced by the dissipation afforded by the heatsink

e.g. 22 watts in device, a 3degC/W heatsink ( including thermal resistance to junction ) will give 66 deg C above ambient, so for 35 deg C ambient = 101 deg C junction.

 

[johncaroline]

I am designing a dc dc boost converter and i wanted to size my mosfet based on Ron value i wanted to know to plot this like i know Ron = (vin-vo)/i but how to plot this in cadence and calculate while using trans anyalsis

In Cadence, you can measure Rds(on) by running a transient analysis. Set up your testbench with the MOSFET in the desired switching condition, then use Vin, Vout, and current probes to measure Ron = (Vin - Vout) / Id. You can use the calculator tool to plot Ron over time by dividing the voltage drop by the current through the MOSFET. Sweep different conditions if needed!