I have have an ADRF6720-27-EVALZ board and I have a problem to set correctly a local frequecy.
I use this board with a very accurate clock source at 28.6MHz (I had verified this frequency with the spectrum analyzer) and I use the internal PLL+VCO to supply che correct working frequency to the ADRF6720.
The problem is the LO_OUT signal that I measure, have a different frequency.
As you can see on the PDF attached, I try with 3 different frequencys and I found always a deviation of any kHz from the value expected:
expected: 360MHz -> real the ouput: 357.41MHz
expected: 600MHz -> real the ouput: 597.01MHz
expected: 1000MHz -> real the ouput: 993.81MHz
For the first 2 case the deviation is about 3MHz and for the lasts is about a 2x3MHz(I think is double because one of 'div2' check at the end of VCO is disabled).
I have the same problem with my custm board.
Why there is this deviation? Any suggestion?