How to eliminate interference between internal and external I/O of a smart controller PAC?

To eliminate crosstalk between internal and external I/O of the intelligent controller PAC, isolation and filtering are required. Internal I/O (such as onboard sensors) and external I/O (such as fieldbus) should be partitioned in layout, with ground planes or slots used for isolation. Signal connections should use optocouplers or digital isolators (such as the ADuM series) for electrical isolation. Common-mode inductors (CML3225A-510T) and TVS protection (SMBJ6.5CA) should be installed at the external I/O input, while RC filtering and ferrite beads (PBZ1608A-102Z0T) should be used for decoupling in the internal I/O circuit.

The power supply should provide independent windings or isolated DC/DC converters for both internal and external I/O. Simultaneously, the operating timing of internal and external I/O should be staggered in the software. Tests show that this elimination scheme can reduce crosstalk between internal and external I/O by more than 60dB, and the system's malfunction rate is less than 0.01% under full load, meeting the IEC61000-4-8 power frequency magnetic field immunity test requirements.