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AD9874 EVAL-BOARD CLK

Question asked by Seregga on Dec 8, 2017
Latest reply on Dec 15, 2017 by Seregga

Hi!

Please help me to adjust Fclk frequency and LC tank

Fif=12.8 MHz, Flo=10 MHz, Fref=26 MHz

I want to get Fclk/8=2.8 MHz on the internal synthezier, so I need Fclk=22.4 MHz.

According to datasheet I need to change register CKN CKR

CKN=112, CKR=130

 

Also I need to adjust LC tank and I don't understand how to calculate it.

According to page 21 Fosc ...

 

Also according to page 23

 

Should I follow to the relation on page 23?

 

On the EVAL BOARD there is C22=22pF, C56 not installed, L3=1.2uH. It seems to be working with Fclk=18 MHz, but Fclk=22.4MHz doesn't work. 

How can I calculate desired Fclk? What should I change on the evaluation board? Please help me. Thank you.

 

Best regards

Sergey

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