Common mode coil for EMI filtering on power supply?

[blapcb]

What is the correct way to specify and connect a common mode coil to a DC/DC power supply for purpose of EMI filtering? Power supply in question is a switcher which takes 8-32v and outputs 5v (which is then dropped with LDO to 3.3v also).

Thanks

 

[mtwieg]

Are you talking about filtering on the output or input?

First you have to identify the source of the common mode current being injected, and the path it takes through the circuit. Normally this involves a detailed schematic of the converter, showing how the circuit ground plane, power source, chassis, and transistor heatsinks are connected.... without knowing that much it's impossible to make a call.