How to optimize EMC feedback in PAC (Power Controller Acoustic Control) encoders?

Optimizing the encoder feedback EMC of the intelligent controller PAC requires addressing signal transmission, power supply, and shielding. The encoder signals (e.g., A/B/Z) utilize differential transmission (e.g., RS422), and a common-mode inductor (CMZ2012A-900T) and TVS (ESDLC5V0D3B) are used at the PAC input.

The power supply provides independent power to the encoder and is isolated via a DC/DC isolator. Shielded twisted-pair cables are used, with the shield grounded at a single point on the encoder and via a capacitor on the PAC. On the PCB layout, the encoder interface circuit is kept away from noise sources. In terms of software, digital filtering is used to eliminate glitches. After optimization, the encoder feedback error under strong interference (EFT 4kV) is less than one count, meeting the IEC61000-4-4 test requirements.