How to suppress interference in the MC analog interface of the motion controller

Suppressing interference at the analog interface of a motion controller requires tailored solutions based on the interface type. For analog inputs, such as torque and speed commands, use an RC or LC low-pass filter at the input, with a cutoff frequency slightly higher than the signal bandwidth. Employ a differential input structure and use an instrumentation amplifier, whose high common-mode rejection ratio effectively suppresses common-mode interference. Provide shielding for the input lines, with the shield grounded at a single point. For analog outputs, such as analog output cards, use an operational amplifier buffer after the DAC output and add an RC filter. Provide extremely clean power to the analog circuitry, typically regulated from the digital power supply via an LDO.

In PCB layout, the analog interface area should be located away from the digital and power areas and have a dedicated analog ground plane. All analog traces should be kept as short as possible. Verify the effectiveness of the suppression measures by measuring the accuracy and stability of the analog signal in an environment with interference.