How to design the noise immunity of a PAC (Power Controller Assembly) hybrid I/O?

The design of a PAC (Power Controller Assembly) for intelligent controllers requires categorized handling of interference suppression for mixed I/O (digital, analog, high-speed, and low-speed). Digital I/O (e.g., relay outputs) uses a ferrite bead (PBZ1608A-102Z0T) in series at the port and a TVS (SMBJ6.5CA) in parallel for transient suppression. Analog I/O (e.g., 4-20mA inputs) uses RC filters (e.g., 1kΩ + 100nF) and isolation amplifiers (e.g., ADuM series) to prevent common-mode interference. High-speed I/O (e.g., pulse outputs) uses differential drive with a common-mode inductor (CMZ2012A-900T). All I/O power supplies are independent and regulated by LDOs.

The PCB layout is partitioned, different types of I/O are isolated, and ground planes separate them. Shielded connectors are used for chassis interfaces, with the shielding layer connected to the chassis. Testing shows that this design enables digital I/O to resist EFT. 4kV, analog IO common-mode rejection ratio (CMRR) greater than 100dB, high-speed IO bit error rate less than 10^-9, meeting the test requirements of IEC61000-4-4, IEC61000-4-6 and IEC61000-4-8;