How to optimize high-frequency logic interference in motion controllers (MC)

Optimizing interference in the high-frequency logic circuit of a motion controller (MC) requires addressing both source suppression and path control. For sources such as clocks, PLLs, and high-speed buses, prioritize chips with spread spectrum capabilities to distribute energy across a wider bandwidth. Connect a small resistor or ferrite bead (e.g., PBZ series) in series at the clock output to slow the rise time. Provide a complete and continuous ground plane as a return path for all high-speed signals, avoiding cross-split paths. During routing, strictly control the characteristic impedance of signal lines and use terminating resistors to reduce reflections. For parallel buses, use resistor arrays or bead arrays for filtering.

Power supply decoupling is crucial; place multiple MLCC capacitors of varying capacitances near the power supply pins of each chip to create a low-impedance path. In FPGA or CPLD designs, properly handle unused I/O pins by setting them to output low or input pull-up to avoid floating. Perform signal integrity and power integrity analysis through simulation to anticipate and resolve potential problems. During testing, use a high-bandwidth oscilloscope to observe signal quality and ensure the eye diagram opening meets requirements.