Low-cost EMC rectification methods for I/O modules

For low-cost EMC remediation of I/O modules, priority should be given to modifying the PCB layout and adding inexpensive passive components. Check the PCB grounding system for optimization; try reducing ground impedance by adding grounding vias and optimizing ground plane connections, which is usually cost-free. Connect ferrite beads in series for noisy power or signal lines; these beads are extremely inexpensive. Add a 0.1μF MLCC capacitor near the chip's power pin; the cost is negligible. Check the capacitance and type of the power input filter capacitor; sometimes replacing it with a different material or adding a small high-frequency capacitor can improve high-frequency emissions.

For radiated emissions, check chassis gaps; try temporarily sealing the gaps with copper foil tape and observe the effect. If effective, consider permanent improvements. For cable radiation, try placing a ferrite ring on the cable. When remediating conducted emissions, try adjusting the capacitance of existing filters. On the software side, if possible, reduce the clock speed or enable clock spread spectrum. Make full use of near-field probes to locate problems and avoid blindly replacing expensive components. Prioritize remediating the most severely out-of-specification frequencies, achieving test requirements with minimal modifications.