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AD9522

Hi,

I'm currently attempting to use the AD9522 Eval to clock my AD9914 Eval. I am using the internal VCO of the AD9522 Eval, but when I externally measure the output signal of my AD9522 I see a different frequency from what the evaluation GUI is telling me it is outputting. When I change the value in the REF1 box, the value that the GUI tells me that it is outputting changes, but nothing actually happens to the output signal.

Do I fundamentally misunderstand how the chip determines it's own output, or is there just some simple mistake I am making?

Thanks!

Arman

  • Hi Armen,

    The AD9522 software does not have an integrated wizard that configures the device for you. It merely uses the currently programmed settings and the reference input frequency and calculates the output frequency based only on that information. If the PLL is locked and your reference input frequency parameter is representative of the actual frequency of the reference input, then the output frequency from the AD9522 will match this calculation. However, if the PLL is not locked then there is no correlation between the input frequency and the output frequency and the output frequency cannot be determined. Could you please use the software to save a setup file and post it here for me to view? It would also be helpful if you let me know the input and output frequencies you had in mind for your configuration if they differ from what the software is displaying.

  • Hi Armen,

    The AD9522 Evaluation Product page has a link to download a configuration tool that will solve the divider settings and loop filter configuration for you. There is also a link to a user guide which explains how to use each block of the software. These should be helpful in getting you up and running with the evaluation board. Just search 'EVAL-9522' in the search bar at analog.com and you can select the Evaluation Page for the version of the AD9522 you are using.

  • I'm using output 5 right now and in an external Oscilloscope I am seeing 173 MHz.

    I have this setup saved on my computer, but I do not know how to post it on one of these threads.

  • I should also add that I have no input to the REF1 or REF2 ports

  • Hi Armen,

    You will need to have a reference input in order to get an exact frequency out. The VCO has a range > 400MHz and needs a reference and a VCO calibration to set the correct amount of capacitance to oscillate at the appropriate frequency. It is also clear from your screenshot that you will need to change the PLL Mode from "Asynch PD" to "Normal Operation" as well as configure your reference input receiver to accomplish this. the user guide located here describes how to do this.

    P.S. To attached files to a post you need to use the advanced editor when adding a comment.

  • This is the setup where the PLL is in normal operation, Reference 1 is enabled, and the VCO is set to Auto Calibration. Right now I have  10 MHz reference signal going into Reference 1. The problem is that the GUI is now telling me I should be getting 120MHz out of port 5, but instead I am getting 150MHz. Are there more settings left to change?

    Arman

    AD9522FixedSetup1.stp.zip
  • Hi Arman,

    Which version of the AD9522 do you have? The screenshot you shared before indicated it was an AD9522-0, but the setup file you have attached indicates it is an AD9522-3. If you clear that up for me, I should be able to determine the register changes required to get this to work properly.

  • Hi Armen,

    Sorry about the delay. Your issue was that you were trying to operate the AD9522-0 VCO well outside of its specified range of 2530 - 2950 MHz. I reconfigured the N divider and output divider to place the VCO in the proper range and still generate 120 MHz out in the attached setup file. I also disabled int he input doubler. As I mentioned before, please go the the AD9522 evaluation page to access the configuration tools we have for this product.

    AD9522_0_10Min_120M_out.stp.zip