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Need help. AD9912 SFDR now limited by SCK feedthrough.

Question asked by DavidLee on Jul 1, 2014
Latest reply on Jul 6, 2014 by sitti

Hi,

I've eliminated lots of spurs in the output of the AD9912 by driving it with a low noise 1 GHz osc, rather than

using the PLL. It works great!

 

Now, my SFDR is dominated and limited by a 50 MHz spur at -65 dBc. This is the serial data clock frequency.

The AD9912's FTW is being updated continuously, and I suspect that this data clock is somehow coupling to the output.

 

I am using the Analog Devices Eval board, Rev B.

 

Is there a spec for SCK feedthrough for the AD9912? I could not find one.

 

Perhaps the problem lies with poor PCB design and layout.

 

A little help?

 

Cheers,

David

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