I am using AD7626 + SDP-H1 as part of my test bench.
I use a clean signal generator with a balun to generate the differential test signal.
I found there is some problem that the captured signal is really not stable after powering on 1 min.
Two figures are the single tone captured directly after power on and the signal captured after 1 min power on.
The ADC were very unstable. Sometimes the FFT looks correct, sometimes not.
I used 'Continuous Capture', and the noise floor were jumping up and down.
If I keep the input port open, I got a noise floor about -120dB.
But if I put 50 Ohm load to each differential input port. And I got figure below that the noise floor is only -50dB.
Could you please help me on that?
Thanks very much