How to design the EMC of the RS485 interface of a power DTU?

Designing the DTU RS485 interface for EMC requires addressing protection, filtering, and isolation.

Protection: A TVS diode (SMBJ6.5CA) is connected in parallel to ground on both A and B lines to absorb transient overvoltages.

Filtering: A series common-mode inductor (CML3225A-510T) suppresses common-mode noise; a parallel capacitor (100pF) filters out high-frequency noise.

Isolation: An isolation chip (ADM2483) is used, providing an isolation voltage of 3000Vrms.

PCB layout: The interface area is separately designated and located away from sensitive circuits.

Testing meets IEC61000-4-2 ESD ±8kV and IEC61000-4-4 EFT ±4kV. A well-designed system ensures stable RS485 communication in industrial environments.