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DDS AD9951 unused pins connection

Question asked by ziopaolo on Jul 3, 2012
Latest reply on Jul 9, 2012 by LouijieC

Good morning. My question is very simple: I would like to know where the unused pins (in case of a single DDS AD9951 design) should be connected?


  1. pin 10 CRYSTAL OUT=unused since CLKMODESELECT (pin 11) is low in my case;
  2. pin 44 SYNC_IN=unused since I have only one DDS;
  3. pin 45 SYNC_CLK=unused since I have only one DDS.


To keep noise from coupling in on those pins, is it better to place a capcitor (=0.1uF) to AGND or it does not matter and they could be left floating? In fact, I was unable to find any hint on the data sheet. Thanks a lot.