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What to do with ADF5355 unused output (RFOUTB)

Question asked by Lionelwallace Employee on Jan 8, 2015
Latest reply on Jun 8, 2016 by rbrennan


I have a few questions regarding the ADF5355 PLL IC.  We intend to use it on two different cards where in both instances the desired output frequency will be between 400 – 6500 MHz.


  1. Since RFOUTB is not used, should the pin be terminated to ground or left floating.  Bit DB10 will be set to 1 to disable output per page 27.  If left floating, is a dc blocking cap recommended to prevent part damage from stray feedback? If grounded, does a 50Ω need to be included since RFOUTB is internally matched to 50Ω impedance?
  2. Page 35 indicates when a single-ended output is desired, a balun may be used in lieu of simply terminating RFoutA-.  How would this affect the performance and quality of the output signal? 
  3. Does ADI have a recommended part that will cover the operational range above?  Is there an application circuit available for said configuration?