抖动是非常重要的，在系统中使用的锁相环

代码说明：

Jitter is extremely important in systems using PLL-based clock drivers. The effects of jitter range from not having any effect on system operation to rendering the system completely non-functional. This application note provides the reader with a clear understanding of jitter in high-speed systems. It introduces the reader to various kinds of jitter in high-speed systems, their causes and their effects, and methods of reducing jitter. This application note will concentrate on jitter in PLL-based frequency synthesizers.