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AD9548 SYSCLK TCXO

Question asked by bijanbina on Feb 12, 2018
Latest reply on Feb 12, 2018 by bijanbina

Hi

On page 23 (Fig. 33) of AD9548 datasheet output of external oscillator is ac coupled to SYSCLKP pin. on the other hand on the evaluation board  both TCXO and OCXO are connected through SYSCLKN pin and FMComms1 Board used 19.4MHz oscillator on SYSCLKP pin. 

I'm wondering which one is correct?

On page 37 in "Choosing the System Clock Oscillator Frequency" section, it mentioned that "the best performance of the AD9548 is achieved when the system clock is not an integer multiple of the DDS output frequency"

but the example 

"As an example, using a 19.44 MHz oscillator for the system clock in a 156.25 MHz Ethernet application yields better performance than a 25 MHz oscillator."

not supporting the recommendation as 19.44 x 8.037 = 156.24

and 25 x 6.25 = 156.25. I believe is 6.25 more far from integer than 8.037. I think that I'm wrong can you help me.

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