Spread spectrum clock generator
US5631920A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 20, 1995 |
| Grant date | May 20, 1997 |
| Priority date | — |
| Expiry date | Apr 20, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2215/067
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A clock circuit includes an oscillator for generating a reference frequency signal, and a spread spectrum clock generator cooperating with the oscillator, generating a spread spectrum clock output signal having a fundamental frequency and reduced amplitude EMI spectral components at harmonics of the fundamental frequency. The spread spectrum clock generator preferably includes a clock pulse generator for generating a series of clock pulses, and a spread spectrum modulator for frequency modulating the clock pulse generator to broaden and flatten amplitudes of EMI spectral components which would otherwise be produced by the clock pulse generator. The spread spectrum modulator frequency modulated the clock pulses with specific profiles of frequency deviation versus the period of the profile. The clock generator circuits are digital and may be reset to a starting condition to synchronize the spread spectrum clock. For a laser printhead, the clock is synchronized with the start-of-sweep signal, so that printing is not degraded.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.