I'm investigating SMPS circuits and I'm trying to design my own.
In my design, I have a 300mOhm current sense resistor and its power rating must be minimum 177mW so I need a 500mW resistor. I have chosen a 2512 SMD package 1W resistor for it.
When I investigated other SMPS circuits that have same specifications (same output wattage & voltage) I noticed that they have through hole type resistors. Is there a reason for it or any reason to avoid using SMD type current sense resistors?
One reason is probably that the surge power capability of larger resistors, especially wire-wound ones, is much better than surface mount resistors. It mainly relates to the thermal capacity of the resistor - large is better in general.
In this application a surge may occur is the supply is shorted, before the current limiting comes into effect.
Your choice of a 2512 2W resistor does seem to be a good one though with a good pulse load capability.
Bourns Thick film resistor
11 things you need to know about resistors in pulse load applications
