Switching Power Supplies A - Z

EMI from the Ground up — Maxwell to CISPR

cases, to avoid last minute delays and a possible redesign, we should err on the side of caution. In this case

that means we should design to Class B limits at the very outset.

Some Cost-related Rules-of-thumb

A brief look at possible costs:

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The FCC spectrum for digital equipment (currently) begins at 450 kHz, while the

equivalent CISPR/EN regulations start at 150 kHz. So FCC compliance can be

achieved with a relatively small and inexpensive filter.

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CISPR/EN Class A compliance often requires a filter with at least twice the volume

of the FCC-level unit. This filter can therefore be up to 50% more expensive.

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