Selection of Decoupling Capacitors to Reduce the Switching Noise

Abstract

Noisy power/ground network can be the major source of radiated emissions, and decoupling capacitors are commonly used to reduce the switching noise between the power supply and the device I/O buffers. This paper presents a simple method for selecting a reasonable value of the decoupling capacitor without an extensive use of circuit simulators. The switching model of power/ground network with a decoupling capacitor is used to formulate the switching noise voltage analytically. The value of the decoupling capacitor can be selected depending on the tolerable amount of the steady-state voltage fluctuation.