Dual Fractional-N Synthesizers/PLLs -- Frequently Asked QuestionsSource: Skyworks Solutions, Inc.
This article is a follow-up to the Skyworks' article Basics of Dual Fractional-N Synthesizers/PLLs that provides a general discussion of the use of fractional-N synthesizers in a low-cost, low-power radio. The article provides answers to a series of frequently asked questions (FAQs) related to fractional-N and their respective evaluation boards.
General questions covered include:
- What are the design trade-offs associated with fractional-N synthesizers?
- What is the primary benefit of fractional-N synthesizers?
- Can I use a lower reference frequency with fractional-N synthesizers?
- What spurs can be expected from fractional-N synthesizers versus integer-N synthesizers?
- What is meant by the term "spur-free"?
- Does fractional-N offer improved phase noise over integer-N?
- Does fractional-N offer improved switching time over integer-N?
Application Note: Dual Fractional-N Synthesizers/PLLs -- Frequently Asked Questions