What does limp mode mean in this sentence below?
Make sure the PLL is not running in limp mode.
Electronic – limp mode in PLL
dsppll
Related Solutions
The Digikey summary table is a generic list trying to show all things to all men. Just ignore it and read the data sheet. Do not rely on it. Same with Farnell - they have a table/list for each component they list - go straight to the data sheet unless its the very basic info you're after.
Generally when you go outside what is recommended the behavior is undefined. It's not guaranteed to work, but neither is it guaranteed not to work. It might work when it's cold but not when it's hot. It might work at 3.3V Vdd but not at 3.29V Vdd. It might work on 19 units and fail on the 20th.
That said, if everything else was nominal (not too hot or cold, power supply near nominal) it's unlikely, in my (somewhat ill-considered) opinion, that they could make it tetchy enough that it would work perfectly at 200MHz and fail at 201, but if it does happen to behave that way you have nobody to blame but yourself.
From the datasheet:
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Best Answer
In this case a PLL in "Limp Mode" would suggest it's still outputting a signal as best it can, however it won't be phase locked like it should
Limp Mode or Limp Along Mode is often a feature used to make sure something will keep running even in the event of certain failures... often seen in cars and planes..
See http://en.wikipedia.org/wiki/Built-in_self-test
Quoting from the wiki
Automotive
Aviation