How can optocoupler isolation improve the immunity of motion controllers?

Improving the immunity of the optocoupler isolation circuit in the motion controller MC requires optimizing its surrounding circuitry and layout. Select an optocoupler with high common-mode transient rejection capability. On the input side, use a series resistor for current limiting and a parallel TVS diode to protect the LED. On the output side, the pull-up resistor value should balance speed and noise immunity; a small capacitor can be connected in parallel to filter high-frequency noise. Provide independent power supplies for the input and output sections of the optocoupler, or at least isolate them with ferrite beads.

On the PCB layout, the optocoupler should be connected across the gap between the input and output grounds; traces on both sides should not be parallel or cross. For high-speed optocouplers, pay attention to the control signal return path. Increase the creepage distance between the input and output pins. Verify the reliability of the optocoupler isolation circuit under high-voltage transients by performing EFT and surge tests. For critical signals, consider using a dual-channel optocoupler redundancy design. The optimized optocoupler circuit can reliably break ground loops and suppress common-mode noise conduction.