How to protect against electrical fast pulses (EFT) in power FTU systems?

EFT (Electrical Fast Transmission) protection (5/50ns) requires a low-inductance path and high-frequency filtering.

Power input: CMZ3225A-501T common-mode inductor (500μH) in parallel with a CY-Y1-222K Y capacitor (2.2nF).

Signal port: PBZ1608E600Z0T ferrite bead (600Ω@100MHz) in series, and ESD5V0D8B in parallel.

PCB design: Power and ground planes are tightly coupled with a spacing of less than 0.2mm.

Grounding system: Star grounding is used, with short and thick grounding wires. The chassis shielding is continuous.

With this protection, the FTU can pass the IEC 61000-4-4 Level 4 test (power port 4kV, signal port 2kV) without malfunctioning during the test.