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AD9959 - continuously repeating rising linear frequency sweep

Question asked by Mikeymike on Nov 23, 2016
Latest reply on Dec 14, 2016 by LouijieC

Hi ADI,

 

Can the AD9959 DDS eval board be configured to perform an autonomous continuously repeating frequency sweep in no-dwell mode?  By autonomous, I mean without using external retriggering signals like the P0-P3 bits or I/O update?

 

It has successfully been done on other DDS parts such as the AD9910 and AD9913.

 

Is this type of sweep possible on the AD9959 and how would it be set up on the eval board to achieve it?  Start and stop frequencies are 40MHz and 75MHz respectively.  The device will be clocked at 500MHz and the RSRR register will be set to give the minimum interval between points (i.e. 8 ns). The no-dwell bit will be set.

 

If it can't do it autonomously, then the profile pins will need to be used to trigger each ramp, but the data sheet is not very specific about the behaviour of the profile pins in this mode.  Thus some question arise:

 

  1. Are the profile pins edge or level-sensitive?
  2. Does a rising edge on a profile pin reset a non-dwell sweep that is in progress?
  3. Will a new sweep only be triggered by an edge occurring after the last sweep has finished?

 

Please let me know.

 

Thanks,

Mike

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