Impact of the layout, components, and filters on the EMC of modern DC/DC switching controllers



The technical literature, including, for example, our “Trilogy of Magnetics” and the IC data sheets, provides hardware developers with all manner of useful tips regarding the design of switching controllers. From the selection of the appropriate power inductor, input/output capacitors, MOSFETs, and Schottky diodes, application examples ranging all the way to a specimen PCB layout are presented that demonstrate how an EMC-compliant design can be realized.

These literature, however, describes hardly any comparative EMC measurements that prove the efficiency of the measures taken. Virtually every state-of-the-art PCB contains one or several DC/DC converters in one form or another. This is why before/after comparative EMC measurements of discretely integrated DC/DC converters give almost all hardware developers an interesting opportunity to deepen his/her knowledge in this area. Since we at Würth Elektronik eiSos are right at home in the EMC area, equipped with the suitable measurement instruments, and are more than glad to assist electronics developers, we have written this Application Note to describe these comparisons in detail.