Datasheet for AD9874 includes parameter "Synthesizer Resolution" with the minimum of 6.25 kHz. What were the originating data for this parameter?
Is it possible to use PFD = 2kHz in LO synthesizer?
It does not appear that anything intrinsically is limiting the PFD frequency to be as low as 2 kHz. I believe the min 6.25 KHz PFD frequency specification was set because the target application was for PMR radio where channel spacing was typically 25 KHz but could be as low as 12.5 or 6.25 KHz.
FYI..............An updated datasheet for the AD9864 was posted recently that contains additional insight into a more robust tuning initialization procedure. This also applies to the AD9874 of which the datasheet has yet to be updated. Regards.