How can intelligent controller PAC IO isolation improve system EMC?

Isolating the I/O of the intelligent controller PAC can significantly improve system EMC. Methods include electrical isolation and ground potential isolation. For digital I/O, optocouplers or magnetic couplers (such as the ADuM series) are used with an isolation voltage greater than 2500Vrms. For analog I/O, isolation amplifiers or isolated ADCs are used. The primary and secondary power supplies of the isolation devices are independent, powered by isolated DC/DC modules (such as 5V to 5V). At the isolation boundary, a common-mode inductor (CMZ3225A-510T) is used to further suppress common-mode noise.

In terms of PCB layout, the ground planes on both sides of the isolation are completely separated with a spacing greater than 8mm, and slots can be opened in the middle. Simultaneously, the shielding layer of the shielded cable for the isolated I/O is grounded at one end on the isolation side. Tests show that I/O isolation can improve the system's common-mode noise suppression capability by 40dB and reduce radiated emissions by 15dB, and pass IEC61000-4-2 ESD 8kV and IEC61000-4-5 Surge 2kV tests.