How to reduce interference at I/O module terminals

Reducing interference at I/O module terminals requires handling signals as they enter or leave the module. Filtering components can be installed directly behind terminal blocks or connectors, such as PBZ series surface-mount ferrite beads and safety capacitors for each signal line group. For digital terminals, ferrite beads can be connected in series on each signal line, and ESD protection devices such as ESD5V0D3B can be connected in parallel. For analog terminals, a π-type filter network should be used, along with high-precision, low-temperature-drift resistors and capacitors to maintain signal accuracy. High-current common-mode inductors, such as CMZ7060A-701T, and filter circuits consisting of X2 and Y2 safety capacitors must be installed at power supply terminals.

PCB layout in the terminal area is crucial; filtering components must be placed as close as possible to the terminal pins. A wide and short copper trace should be used between the ground pin and the module's internal ground plane to ensure a low-impedance return path. The terminal metal casing should have a good low-impedance connection with the module chassis to provide a discharge path for high-frequency interference. For high-density terminals, connectors or filter array modules with integrated filtering functions can be used to save space and ensure consistency.