How to protect against EFT (Electrical Fast Pulse) in concentrators?

The concentrator needs to withstand IEC 61000-4-4 EFT/Burst interference, characterized by high frequency, high voltage, low energy, but wide coverage. Protection requires multi-level coordination: at the power input, a common-mode inductor CMZ1211-501T combined with a Y capacitor (2.2nF/Y1) provides a low-impedance return path for common-mode pulses. A π-type filter (PBZ1608E600Z0T ferrite bead + capacitor) is added before the board-level DC/DC input. For the communication port, a common-mode inductor CML3225A-510T and a TVS diode (such as SMBJ6.5CA) are used. PCB layout is crucial: all filtering and protection devices must be located close to the interference entry point (connector), and traces before and after the filter must be separated. The grounding system must be low-impedance and complete. On the software side, digital filtering is applied to potentially affected input signals, and error checking and retransmission are enabled for communication. Through design, the concentrator can stably pass the EFT Level 4 test (4kV) without malfunctioning under pulse burst interference.