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Granularity of frequency in the AD9834 DDS

Question asked by bjcolo on Jun 25, 2015
Latest reply on Jun 25, 2015 by bjcolo

What clocks the chip? is it the MCLK or is it the numerically controlled oscillator (NCO)?  Though the text implies it, I don't see anything in the documentation showing an oscillator whose frequency is controlled as finely as 1 part in 2^28.  How is this possible?


It seems more logical that the MCLK clocks the chip.  But if that were so, an MCLK of 50MHz producing a 1MHz output frequency would have a granularity of 1 part in 50 - way too coarse.


My circuit does actually achieve frequency granularity of something like 1 part in 2^28 - I LOVE IT!  But how is such a finely tuned oscillator possible and how does it relate to the MCLK?