How to design the MC bus port filter for a motion controller?

Designing filtering circuits for various bus ports of a motion controller (MC) requires consideration of bus characteristics and noise frequency bands. For differential buses such as EtherCAT, Profinet, and CAN, common-mode chokes are used on the signal lines to suppress common-mode noise. A low-capacitance TVS diode array is connected in parallel for transient protection. For single-ended buses such as UART, a low-pass filter can be constructed by connecting a ferrite bead in series on the signal line and a capacitor in parallel to ground. All filtering and protection devices should be placed close to the connectors. Decoupling capacitors should be added to the power supply pins. The filter's ground terminal must be connected to a clean, low-impedance ground plane, ideally connected to the internal digital ground via a single point on the ferrite bead. During design, care must be taken to ensure that the filter's bandwidth does not affect the bus communication rate. The impact of filtering on signal quality is evaluated by measuring the eye diagram and jitter of the signal before and after filtering. Finally, the effectiveness of the filtering design must be verified through appropriate bus protocol compliance tests and EMC immunity tests.