How to optimize the auxiliary power supply filtering of the motion controller MC

Optimizing the filtering design of the MC auxiliary power supply for a motion controller requires ensuring it provides a clean voltage to the control circuit. The auxiliary power supply is typically a low-power switching power supply or an LDO. For switching power supply types, a π-type filter should be placed at its output. PBZ series ferrite beads can be used as inductors, and a combination of low-ESR MLCCs and tantalum capacitors should be used to cover everything from low-frequency ripple to high-frequency switching noise. If the auxiliary power supply powers multiple circuits, LC filters or ferrite beads should be added to each branch for isolation. For noise-sensitive circuits such as PLLs or reference voltages, a separate LDO can be used for secondary regulation.

The grounding terminals of all filter capacitors should be directly connected to a quiet ground plane. In terms of layout, the auxiliary power supply module should be kept away from noise sources such as motor drive circuits, and filtering components should be placed close to the power output pins. The filtering effect can be evaluated by measuring the ripple and noise spectrum of each power supply node. If noise is prominent at specific frequencies, ferrite beads can be added or capacitor values adjusted accordingly. Where cost allows, a lower-noise linear power supply can be considered for powering critical circuits.