EMI Bites: Connect Ground Planes to Prevent EMI Emissions
EMI Bites: Connect Ground Planes to Prevent EMI Emissions
A critical PCB design flaw is assuming copper "ground" planes are zero volts and all inherently equipotential.
Any metal, including ground planes, has electrical characteristics like resistance and impedance.
If two ground planes are poorly connected between each other, they develop different potentials, creating voltage drops that potentially induce common mode currents and elevate EMI emissions.
The solution?
Use stitching vias, spaced at one-tenth of the high-speed signal’s wavelength in the dielectric (e.g., FR4), to ensure equipotential planes.
This minimizes impedance, prevents reflections, suppresses common mode noise, and enhances EMC compliance.
-Dario
P.S. Want more EMI control strategies to pass EMC?