How to improve the conducted immunity (CS) of a power FTU?

Improved conducted interference immunity (CS) requires enhanced power supply and port filtering.

Power supply filtering: A three-stage π-type filter is used, consisting of a CMZ7060A-701T common-mode inductor, a 470μF electrolytic capacitor, and a PBZ2012E600Z0T ferrite bead.

Port filtering: A PBZ1608E600Z0T ferrite bead is connected in series at the signal port, with parallel ESD protection.

Grounding optimization: A low-impedance star grounding configuration is used, with the grounding wire shorter than 10cm.

PCB design: The filtering circuit is located close to the interface, and the power layer is intact.

With these improvements, the FTU can pass the IEC 61000-4-6 CS test (10V, 150kHz-80MHz) without communication interruption and with a sampling error of less than 1%.