In this snippet from Trace Talks, legendary EMC expert Dan Beeker joins Amit Bahl to break down one of the most misunderstood aspects of electromagnetic compatibility:
It’s not the switching output that causes the problem, it’s the depletion of energy when a switch turns on.
Using his classic hose analogy, Dan explains how voltage drop from poor power delivery creates high-speed depletion waves. These waves—confined to a quarter wavelength—become the source of radiated emissions when designers fail to control electromagnetic energy across the board.
The culprit?
- Separating power and ground
- Ignoring the one-dielectric rule
- Stack-ups that don’t support high-frequency behavior
- And above all: not placing energy where the IC needs it when it needs it
Dan’s insights challenge outdated EMC assumptions and highlight why power integrity is signal integrity. If your board radiates, it’s likely not a switching issue, it’s energy gone rogue.
Have you dealt with depletion wave-related EMI? Or designed with Faraday’s law in mind? Drop your take below, we’d love to hear how you manage energy on your board.
Watch Dan Beeker discuss power supply and challenges in Trace Talks EP 1.