Procedure for the Selection of Decoupling Capacitors

This paper examines conducted electromagnetic emission of an integrated circuit, combined with a step by step guide for the optimal selection of decoupling capacitors to reduce the emission in certain frequency ranges. The approach addresses the determination of the parasitic inductances of the capacitor and the loop that is formed when the decoupling capacitor is connected next to an integrated circuit on a printed circuit board. On the basis of measurement examples of a demonstrator board prepared for laboratory exercises, it is shown how an efficient selection for the right decoupling capacitor can be found.