Hi we are looking to add pi filters at the input of the buck regulator for EMC. We are using two buck regulators in our design, MPQ4321 for 3V3 regulation and MPQ4326 for 3V8 regulation. Our question is for better EMC do we have to use a separate pi filters at the input of each of the buck converter or one common pi filter will be enough.
A single pi filter should suffice for both converters if they are on the same PCB.
Ideally, the pi filter should be placed near the connector, on the opposite layer from the DC/DC converters to avoid noise coupling.