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ADF4351 reference boundary spur when DIV=1

Question asked by amir_al on Jul 28, 2013
Latest reply on Jul 29, 2013 by icollins

Hi

 

I am using the ADF4351 in two of our products and see a problem with the reference boundary spur when the synthesizer is set to 2.2GHz and up (i.e div=1). i'm seeing results of about 30 - 40 dBc when the frequency is set in a way that the loop filter isn't rejecting the ref boundary spur, lets say 2260.01GHz. this is happening every 10MHz or 20MHz depending if the ref doubler is on or off.

 

I see this problem on both our circuits and on the eval board (EVAL-CN0285-EB1Z).

 

I am using a 10MHz reference.

 

2260.01 registers.png

 

2260.01 int boundry spur.png

 

Thank you

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