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AD4351 Reference Spurs, Integer-N mode, f_PFD=25 MHz

Question asked by Evan.Zalys on Feb 24, 2018
Latest reply on Feb 26, 2018 by Evan.Zalys

Hello! I'm struggling to get the AD4351 to produce something with reduced reference spurs.

 

Here's the output from my specan Imgur: The magic of the Internet 

 

It's set in integer-N mode, and it's got a 25 MHz crystal as a reference. Aux output disabled, 50 ohm match on A-, specan on A+. INT=100, r-counter=1, ref div=0, ref doubler=0. Changing the charge pump current doesn't seem to do much. Any idea what's up? I'd expect reference spurs to be at the level of -80 dBc.

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