What is the best PLL configuration for your app--and how do you find it? Erik Mentze， Sr. Systems Engineer， Cypress Semiconductor 作者：Erik Mentze，高级系统工程师，赛普拉斯半导体 The goal of any frequency synthesizer is to generate a desired output frequency based on a given input reference frequency. However， this relationship between available input frequency and required output frequency is not always obvious. The question always looms: Is there another， better configuration for my PLL that will deliver better noise performance and lower power? Sometimes the question is a critical as whether the current hardware is even able to meet new requirements (does a solution exist?) This article introduces a method for finding all possible PLL configurations (using integer divide PLLs) that can meet a given set of input / output frequency requirements. A metric is then applied to this complete list of configurations to determine the best configuration for your specific application.
任何频率合成器的目标都是根据一个给定输入参考频率产生一个期望输出频率。然而，可用输入频率和所需输出频率之间的关系并不总是显而易见的。总会有很多问题出现：我有没有选择最好的频率合成技术参数？可能还有另外的设置可以使频率更干净、电源消耗更少？有时候问题很苛刻，现有硬件是否能满足新的需求（存在解决方案吗?)。本文将介绍一种可以找到所有可能的锁相环配置(使用整数分频PLL)的方法，这些配置可以满足给定的输入/输出频率要求。运用一个完整的配置列表，为您的特定应用确定最佳配置。
Before we can setout to find the optimal configuration for our PLL， we need to first consider how we find any configuration for our PLL. Specifically， we will need to be able to find all of the possible configurations that our PLL can use for a given reference oscillator and desired output frequency. Once we are able to confidently generate the list of all possible configurations that satisfy our needs， we can then choose which one is best. Actually， the bulk of the work in determining an optimal PLL configuration is wrapped up in determining the list of all possible configurations that meet our needs. As such， this article will first focus on determining all possible configurations， then wrap up with selecting the best option.
在我们准备为锁相环找到最优配置之前，首先要考虑如何找到锁相环的所有配置。特别是，我们需要能够找到可以用于给定参考振荡器和期望输出频率的所有可能的锁相环配置。一旦我们能够产生满足需求的配置清单，我们就可以选择出哪一个是最好的。实际上，确定PLL 最优配置的大部分工作是确定所有的满足我们需求的配置清单。因此，本文首先将集中在确定所有可能的配置方面，然后讨论如何选择最佳参数。
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