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.