Well Grounded, Digital Is Analog

Abstract: An inexperienced designer may think that power decoupling capacitors and grounds are magic mystical things that absorb every bad noise. They are not. This application note discusses proper capacitor selection. It explains the failure of capacitors to decouple power buses above their self-resonance point. To illustrate the forces and characteristics of capacitors on a ground plane, an analogy to electrons is used. Electron behavior is comically illustrated. Guiding currents toward the ground star point in ground planes is demonstrated by slotting the plane.