EMI Bites

If you're battling random resets, frozen boards, or EMC test failures, chances are these common pitfalls are at play.

I've compiled my top 10 mistakes that trip up even seasoned designers—rooted in overlooking electromagnetic fields and parasitics.

Remember, think fields, not electrons, to channel energy properly and avoid black magic fixes.

- Not choosing the appropriate stackup for your board.

This sets the foundation. Wrong layer pairs mean fringe fields escape, crosstalk spikes, and you're back to respins. Always pair layers wisely—don't skimp here.

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Just don't.

When I inquired about the presence of this earth safety wire on this power supply, the manufacturer responded with:

"Oh, no, this is not really for safety; this is actually to improve EMI. Without this, we could not pass EMC tests."

This tells me that many things in this design are not well understood, in particular parasitics.

The difficult part in understanding parasitics is that they are not designed in the schematics.

The issue is that we have not been taught right from the beginning.

We learned that electrons are the protagonists of the electromagnetic fields story of propagation.

This leads us to learn to build circuits with electrons flowing through the copper in mind, instead of electromagnetic field channels.

Once I learned these simple fundamentals—that is, fields that carry the energy of the signal, not the electrons—it all changed.

You can then picture how you need to build channels to contain the fields, instead of single strings of conductors to carry the electrons inside.