How to design a motion controller using the MCEtherCAT bus EMC?

The EMC performance of the motion controller's MCEtherCAT bus must adhere to its physical layer specifications and incorporate additional protection. EtherCAT uses differential transmission, requiring strict control of the differential pair impedance on the PCB to 100Ω and ensuring equal length. Sufficient high-frequency decoupling capacitors should be placed on the power pins of the PHY chip. The network transformer is a critical EMC component; a model with a center tap and good shielding should be selected, with the center tap connected to the chassis ground via a high-voltage capacitor.

A common-mode choke can be added after the RJ45 connector to enhance common-mode rejection. Low-capacitance TVS diode arrays should be used for ESD and surge protection of signal lines. Shielded Cat5e or Cat6 cables should be used, with the shield grounded 360 degrees at the controller end. During PCB layout, the Ethernet area should be kept away from noise sources. Radiated emissions and immunity, particularly resistance to EFT and surges, should be verified through testing. Compliance with IEEE 802.3 and IEC 61800-3 requirements is essential.