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AD9517-1 Ext Clock and Internal VCO Simlutaneously

Question asked by billrad on May 6, 2018

Can the AD9517-1 be configured to operate the internal VCO/PLL AND also accept an external clock for distribution, without connecting that external clock to the N-divider?

 

It appears that the ext clock input is ONLY intended to be used with an external VCO.  And when the ext clock is selected, the N counter is connected to this clock input and NOT the internal VCO.

 

I want to connect the internal VCO to the N-divider, and use the ext clock input for distribution.

 

The block diagram appears to show different muxes between the paths, but it appears they are not individually settable.

Are there register settings that could make the needed connections?

 

My situation requires use of the STATUS pin to output the prescaler divider (few 10s of MHZ) with the PLL locked (i.e. a low freq phase-locked output), but also accept an ext clock for distribution.  But, when I select the ext clock (0x1E1), the PLL looses lock (since the N-divider is disconnected from the VCO)

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