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ADF4351 PFD Frequency

Question asked by Tak-8810 on Oct 2, 2013
Latest reply on Jan 6, 2014 by icollins

Understanding of the following is correct about ADF4351?

 

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Value of PFD frequency is calculated by the following equation.
fpfd = REFIN × [(1+D)/(R×(1+T)] (Data sheet Page.11)

 

So, Value of 125kHz(DB23 bit of R3 is 0) is calculated by the following equation.
fpfd = 250MHz × [1/(1023×(1+1))]

 

This value is used as the clock for the band select logic.
When using a value greater than 125kHz in Low PFD mode,

there is a possibility that the band select logic to malfunction.

 

When the required PFD frequency is higher than 125kHz, the divide ratio

should be set to allow enough time for correct band selection.

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