Noise Generated using differential pmods as single ended

Started by abdul_samad 4 years ago1 replylatest reply 1 month ago53 views


I have a zedboard and a nexys video artix 7 board. I am generating a sinusoid from DDS Core of the same frequency (by supplying the same phase increment and the same clock frequency to both cores) on both boards and outputting the result on DAC2459A parallel DAC. Unfortunately I am out of single ended Pmods on the artix 7 board so I am using differential pmods as single ended by using p and n pins of the same  port for different signals. However when I compare its output to the output of single ended pmods on the zedboard there seems to a more noise, a slight frequency shift and an elevated noise floor. Could anyone suggest me any technique for converting differential pmod outputs as single ended. I am thinking of declaring the n part as permanent ground output and supplying the signal on p parts. But there is still significant noise even in this method.

Best Regards

Abdul Samd Usman

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Reply by engineer68February 16, 2023

Did you connect the signals correctly? There is no reason to GND anything in this case. In the opposite, the PINs should be used as outs only, according to my understanding.

One issue could be, that you do not register the signals and observe glitches. 

And / or there might be some SSO-problem of switching outputs and differences in grounding at the various ports.