Spread Spectrum Clock Generator (SSCG) User Guide

Electromagnetic Interference (EMI) is a major challenge for designers of electronic devices. In the US, the Federal Communications Commission (FCC) tightly regulates the maximum amount of EMI that any electronic device may emit. The FCC regulations are designed to make sure that electronic devices will not interfere with each other. EMI will be generated when the system is working based on frequency reference.

The technique, which involves modulating the reference frequency, is able to substantially reduce the amount of EMI created by the frequency reference and is often called "spread spectrum." The Fujitsu Spread Spectrum Clock Generator (SSCG) family includes a variety of devices that modulate clock frequencies to attenuate peak emissions in computers, printers, MP3 players, cell phones, and other products that operate at increasingly higher frequencies. This application note introduces the Fujitsu SSCG, its key benefits and design guidelines and is intended to help system designers select a SSCG solution.