How to control common mode on MCCAN bus in motion controller?

Controlling common-mode interference on the MC CAN bus of the motion controller is crucial for ensuring reliable communication. A common-mode choke, such as the CML series, is used at the CAN interface. Specifically designed for CAN buses, it provides high common-mode impedance at high frequencies without affecting differential signals. An ESD protection diode or TVS diode, such as the SMBJ series bidirectional TVS, is connected in parallel between the CANH and CANL lines and ground. Shielded twisted-pair cable is used for the CAN cable, with the shield grounded at a single point on the controller. Termination resistors must be 120Ω and placed at both ends of the bus.

During PCB layout, a complete ground plane should be provided below the CAN transceiver, and its power supply must be adequately decoupled. If there are multiple CAN nodes in the system, ensure that the ground potentials of each node are not significantly different; otherwise, isolation should be considered. Injecting common-mode interference into the CAN bus tests the communication bit error rate, verifying the effectiveness of the control measures. Good common-mode control enables the CAN bus to operate stably in harsh industrial environments.