I'm trying to reduce some switching noise I'm seeing (using LISN & Spectrum Analyzer) on my input power cable. My SMPS operates at 1.2MHz. I have room on the PCB and I'd like to place a SMT common mode choke with a couple of filter capacitors on the input and output of the choke. I was hoping to make a sort of Pi filter.
The device will use 12V from a vehicle cigarette lighter at approximately 75mA. I believe the output resistance of the car battery is relatively low.
I've looked at this Murata Noise Suppression PDF and I see a few examples of possible solutions but no Pi filters.
Any suggestions? Am I going at it all wrong?