AD9956 outputs clock at 400mV, I was expecting 1.8V.

Question

I have the AD9956 eval board and am feeding in a 1V peak to peak 400MHz ref clock. I am able to generate an output clock at 50Mhz, but its only 400mV peak to peak. The logic bus this runs into operates at 1.8V, and I was expecting this clock to output around there. Any idea what I could be doing wrong? Or is this part intended to output the clock voltage around 400mV peak to peak?

Jules.Nikko · Accepted Answer

Hi dantravis , 
 Based on the values you gave, the numbers are still normal. That means you're doing it right. The intended output clock voltage should be around 400mV peak-to-peak. 
 From the datasheet, here is the graph of AD9956 at 400MSPS Clock, 40MHz which is close to your given values. Based on this graph, it generates approximately -5dBm which means it is 356mV peak-to-peak. 
 
 To answer your question, yes. You are still doing it the right way and that is the expected output voltage. 
 All the best, 
 Jules

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AD9956 outputs clock at 400mV, I was expecting 1.8V.

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