EMI Bites: Crosstalk and Missing Planes Spell EMI Trouble
EMI Bites: Crosstalk and Missing Planes Spell EMI Trouble
Your PCB might look ready to shine, but small design oversights can create major electromagnetic interference (EMI) headaches during certification testing.
The biggest troublemakers?
Signal traces packed too tightly together and missing Return Reference Planes (RRPs).
But why do these seemingly minor flaws cause such big problems?
- Crosstalk: When traces run too close together, their electromagnetic fields interfere with each other, creating noise that corrupts your signals and ruins signal integrity.
- Cable-amplified emissions: Noisy traces connected to external cables turn those cables into unintentional antennas, broadcasting EMI far beyond your board.
- No RRP: Without a dedicated reference plane, electromagnetic fields from your signals spread uncontrolled throughout the PCB, increasing both radiated emissions (through the air) and conducted emissions (through power connections).
Here's the key insight: Signals follow the laws of physics, not your design intentions—they demand proper impedance control and field containment!
These mistakes transform your carefully designed PCB into an EMI broadcasting station.
My go-to fixes for clean, EMI-compliant designs:
- Space traces at least three trace widths apart
- Add a uniform RRP beneath signal layers
- Route signals to minimize cable connections
- Check layouts early to catch tight trace clusters
—Dario
P.S. Want more EMI control strategies to pass EMC?