How to design the EMC of the RS485 interface of the concentrator?

The concentrator's RS485 interface is used for long-distance communication and requires a complete EMC design to withstand surges, EFTs, and common-mode interference. A TVS diode (e.g., SMBJ6.5CA) is connected between the A/B lines for power and ground for differential mode protection, and a bidirectional TVS diode (e.g., SMBJ12CA) is connected between the A/B lines and ground for common-mode protection. A series common-mode inductor CML3225A-510T (51μH) is used to suppress high-frequency common-mode noise. A 120Ω matching resistor and a 10Ω current-limiting resistor are connected in series at the transceiver front end. An isolated RS485 transceiver (e.g., ADM2587E) is selected, with its isolation power supply using a DC/DC module. PCB layout: protective filtering components are placed close to the connector, and the transceiver is close to the connector. The connector uses a metal housing, and the housing is connected to the chassis ground. Shielded twisted-pair cables are used, with the shielding layer crimped 360° to the chassis ground at the concentrator end. This design meets the severe requirements of IEC 61000-4-5 surge ±4kV, EFT ±4kV, and ESD contact ±8kV.