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AD9578 frequence calculation formula puzzle

Question asked by Verti on Aug 25, 2016
Latest reply on Aug 31, 2016 by Verti

Dear  SteveBeccue and ADI technical experts,

           Sorry to trouble you.

          After we read the AD9578 datasheet, we got confuse with below description, if the analysis progress is wrong please kindly help to correct it.

a. In Page 26. calculation formula shows in Fractional Mode,

b. In Page 28, we got register Settings for Various Output Frequencies with a 49.152 MHz Crystal.

Take the first line data for example, if PLLX feedback divider=71.207682292, put it into calculation formula, the result is 3527Mhz



c. Go to Page27, if PLLX frequency select = 9,however the calculated data 3527Mhz is over range...that's the problem..