How to design wiring near I/O module terminals

The routing design near I/O module terminals directly affects the EMC performance of the ports. Filtering and protection devices, such as TVS diodes, ferrite beads, and safety capacitors, must be placed close to the terminal pads, and traces should pass through these devices before entering the internal circuitry. Connections between signal pins and corresponding filter device pins on the terminals should be short and straight to avoid loops or antennas. Ground pins should be connected to the internal ground plane via wide, short traces or directly through copper pours to create a low-impedance noise discharge path.

For high-speed differential signal pairs, the differential pair symmetry should be maintained at the terminals, and the signal should immediately enter a common-mode choke. Filtering inductors and large capacitors at power supply terminals should also be placed nearby. In multilayer boards, all layers below the terminal area should ideally be ground planes to provide shielding and good return current. Routing should avoid running unrelated signal lines on other layers below the terminals. After design completion, thermal simulation and current density analysis can be used to check the reliability of terminal connections, and ESD and surge tests can be performed to verify port robustness.