EMI/EMC Academy ~30 min Interactive

Cables, Connectors & Filtering

Cables carry bursts straight to your circuits. Common-mode chokes, connector filtering and shield bonding are the front line.

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Just as cables dominate radiated emissions, they dominate EFT ingress — the clamp couples onto the whole bundle. The most effective single fix is a common-mode choke at the connector, which presents high impedance to the burst's common-mode current while passing the differential signal untouched.

Learning objectives. Use CM chokes and connector filtering for burst immunity; bond shields 360°; and place protection at the point of entry.

Filter at the connector, before the burst reaches the board: CM choke, common-mode/Y-caps to chassis, and a short bond from cable shield to chassis. A shielded cable helps only if its shield is bonded 360° — a pigtail's inductance lets the burst straight through, exactly as in the Pre-Compliance cables module.

Symmetry with emissions. The same CM choke + 360° bond that cuts radiated emissions also blocks incoming bursts — fixes are bidirectional.

Ferrite quick test. A snap-on ferrite at the connector is a fast bench check: if immunity improves, design in a proper CM choke.

Common mistakes: a Y-cap that isn't safety-rated on a mains port; a CM choke placed after the noise has already entered the board; or relying on a cable shield terminated with a pigtail. Each looks like protection but leaves the burst path open.

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