While spread-spectrum clocking has long since been used in processor and memory clock trees, there are many other clocked systems, such as power supplies or switch-mode amplifiers, that continue to use a single-frequency clock. This can, in turn, generate significant EMI and can make meeting governmental regulations for EMI challenging. These regulations typically set a limit on peak energy within a narrow frequency range. Spread-spectrum techniques vary the period of the clock to distribute the energy over several frequencies, thus reducing the amplitude of the central peak.
This document describes a method of generating a spread-spectrum clock source using a low-cost low-power MSP430 microcontroller from Texas Instruments.