How to select a power filter for an I/O module

Selecting a power filter for I/O modules requires consideration of interference type, voltage and current ratings, and mounting method. First, determine the noise frequency band that needs suppression. Common-mode noise primarily relies on common-mode inductors, such as the CMZ series, whose impedance-frequency curve should have a high value within the noise band. Differential-mode noise relies on X capacitors and differential-mode inductors. The rated current should have a margin of at least 1.5 times the rated current, and the impact of temperature rise on performance should be considered. For industrial environments, filters with relevant safety certifications such as UL and CE should be selected, and the leakage current of their Y capacitors must meet safety standards.

Regarding mounting methods, PCB-mounted filters, such as the PBZ series, are suitable for board-level integration, while stand-alone metal-cased filters are suitable for chassis entry points. When selecting a filter, pay attention to its insertion loss curve to ensure sufficient attenuation within the target frequency band. For modules powered by switching power supplies, the filter should have good suppression at the switching frequency and its harmonics. Finally, environmental factors must be considered; for example, in high-temperature or high-humidity environments, components made of appropriate materials should be selected. In practical applications, a near-field probe can be used to test the noise spectrum on the power line for targeted selection.