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AD9637-80 Digital output timing at 75Msps

Question asked by Niels on Jun 23, 2015
Latest reply on Jul 8, 2015 by DougI

Hello,

 

I am using the AD9637-80, and it works fine up to 65Msps.

But when I increase the sampling frequency to 75MHz, I get corrupted data.

I checked the timing with my scope, and found that at 65Msps (=780Mbit/s line rate), I see the data lines changing app. 600ps after the DCO edge.

But at 75Msps (=900Mbit/s line rate), I found that data changes app. 90ps prior to the DCO edge.

 

For a better visualisation of the problem, I attached two scope shots, taken at 65Msps and 75Msps.

CH1 and 2 are always DCO+-

CH3 and 4 are always D+-H

 

Can you explain this behavior to me?

 

Thanks in advance,

Niels

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