The effects of jitter range from none at all to complete system failure. This article describes jitter and its causes and effects and shows you how to reduce it.
Frequency synthesizers use PLLs to generate frequencies from reference sources.
Although some PLL-based systems use more than one reference, a system can generate multiple frequencies from a single reference. For example, one Cypress CY2291 clock generator replaces many traditional metal-can oscillators on a PC motherboard. This replacement results in a significant reduction in board space and cost. Note that the PLL offers two types of correction. The first type is a frequency correction for large differences between the reference and feedback inputs.