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Question regarding ADF4351 fractional modulus value (MOD)

Question asked by Matt1012 on Mar 15, 2016
Latest reply on Mar 30, 2016 by rbrennan

Hi,

I have one question regarding ADF4351 fractional modulus value (MOD).

As demonstrated  that ‧MOD = REFIN/fRES  in the datasheet:  The choice of modulus (MOD) depends on the reference signal (REFIN) available and the channel resolution (fRES) required at the RF output.

And also : The 12 MOD bits (Bits[DB14:DB3]) set the fractional modulus. The fractional modulus is the ratio of the PFD frequency to the channel step resolution on the RF output.

what if the value of MOD doesn't equal to an integer (for example fPFD=REFIN=13MHz, and channel resolution at the RF output=200kHz, )

Based on the equation, MOD=13MHz/400kHz=32.5

But based on the ADF4351 tool, MOD=13.

 

 

How does MOD=13 comes from? Is there any documentation I could refer ?

 

 

Thanks.

Matt.

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