Placement Pi-Filter Inductor

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Hello,

why does PI recommend for the Pi-Filter Inductor to be placed between the negative terminals of the input filter capacitors?
What would be the impact for placing it between the positive terminals?

Thanks for your support!

Hello hardwaredev,

The pi-filter inductor can be placed either between the negative terminals or between the positive terminals. In theory (i.e. the math), the differential-mode filtering is the same.

In practice, however, there may be advantages one way over the other because of layout restrictions, parasitics, and noise.

You may find the following appnote useful:

https://ac-dc.power.com/sites/default/files/product-docs/an15.pdf

Because EMI depends on so many factors including the PCB layout, magnetics, cabling, etc., it is prudent to verify compliance for your particular solution.

-PI-ODO