A practical guide to the theory, operation, and selection of spread spectrum clocks - Replacing an original clock source with a spread spectrum clock oscillator achieves a significant, systemic reduction in EMI

摘要

A SPREAD SPECTRUM CLOCK is a special type of digital clock that provides lower electromagnetic interference (EMI) outputs when compared with conventional clock generator outputs. Reducing the amount of EMI radiated from an electronic device is one of the hardest problems to resolve in today's drive for lower production costs. Producing a compliant device suitable for Glass A or Class B consumption can be quite costly if the necessary steps are not taken at design time. Most digital and system design engineers have been formally trained in the area of their expertise and can provide a working product; but when the product is handed over to the EMC engineer, it soon becomes apparent that the application under test has many EMI problems. It is conceivable that 40 to 50 percent of the development cost of a new product can be spent in the quest for a compliant product suitable for production.