Spread-Spectrum Clock Chip Is Frequency-Programmable

The SG521/2/4/8/9 family of spread-spectrum clock-generator circuits is designed to reduce system-wide EMI by from 8 dB to 20 dB. To achieve EMI reduction, the output clock is frequency modulated with a low-frequency carrier. This distributes the peak energy of the clock over the sidebands and allows systems to pass increasingly stringent EMI standards. Using a single crystal-oscillator input of 14, 44 or 48 MHz, the SG52X family provides digitally programmable frequencies from 10 to 120 MHz.Because the chips provide digital frequency programming, OEMs can inventory a single spread-spectrum clock generator for multiple applications. The ICs operate from a 3V to 5V supply.