Nonprofit CiA (CAN in Automation) association has released the CiA 110 CAN common mode choke specification as a Draft Specification Proposal (DSP).
The 14-page document specifies requirements and test methods of the mechanical and electrical parameters of common mode chokes to be used in Classical CAN networks and CAN FD networks. The electromagnetic compatibility evaluation complies with the IEC 62228-3:2019 standard.
Electromagnetic emission from a device through the CAN transceiver can be filtered by means of common mode chokes, thus limiting unwanted high-frequency noise on the CAN network lines. Using a common mode choke helps to improve the susceptibility and immunity of the CAN transceiver to electromagnetic disturbances on the CAN network. While the above-mentioned effects of the common mode choke are beneficial, unexpected results can occur under certain conditions. Electromagnetic compatibility susceptibility can be degraded in some frequency ranges, bus-signal integrity can be worsened and very high-transient voltages under bus-failure conditions can be generated.
This can lead to a CAN transceiver damage. Care should be taken in the choice of common mode choke along with the termination and protection scheme of the device and on the network-lines in order to prevent a damage on the CAN transceiver or other network components.