I have run into an unexpected issue with AD9557 evaluation board. As you can see in the screenshot from the settings, I provide XOA sine wave input of 50 MHz, the reference clock frequency is 80 MHz, and I expect to get 80 MHz on the output as given by the evaluation board software. However, the resulting output frequency is 77 MHz. The image of the scope screen shows all 3 signals and the measured frequencies (yellow XOA 50 MHz, red-RefA 80 MHz, blue output A - 77MHz instead of expected 80 MHz.
Also, I'm never able to achieve phase and frequency lock in the PFD that is connected to RefA.
Could you advise how to resolve this?