How to improve the conducted immunity of I/O modules?

Improving the conducted immunity of I/O modules hinges on preventing interference from coupling into the module through power and signal ports. At power ports, high-performance EMI filters are used, incorporating common-mode inductors, X capacitors, and Y capacitors, such as integrated power modules or discrete π-type filter networks. These filters must have sufficient insertion loss in the 150kHz to 30MHz frequency band. For signal ports, filters are configured according to signal type: RC filters for low-frequency analog signals and common-mode chokes with TVS protection for digital signals. All filters must be grounded with low impedance and a "clean" surface to prevent noise coupling through the ground wire.

Internally, shielding is added to the switching power supply, and local LC filtering or LDOs are added to the power supplies of sensitive chips. On the PCB design, ensure tight coupling between the power and ground planes to provide a low-impedance noise return path. At the system level, using an isolation transformer to power the entire device significantly improves immunity to conducted interference from the mains. Improving conducted immunity is a systemic issue requiring comprehensive measures in port filtering, internal circuit design, and system installation, and must be verified through CS testing.