AVDD of my AD7655 is powered by analog 5V, DVDD and OVDD are powered by 5V and 3.3V digital power respectively. The 3.3V of OVDD is obtained after DVDD is converted by LM1117 module. After I connect the sine wave output by the signal source to the analog input of the ADC, as long as the digital power is turned on, I will see that the sine wave on the oscilloscope is mixed with noise, and the noise is very regular. There is a lot of noise mixed in the sine wave. I would like to ask how to solve this noise from the circuit? Even if I filter the input signal through RD, the noise can be seen on the oscilloscope, but the signal sampled by the ADC still has this noise
After the sine after superimposed noise is sampled by adc, the graph drawn by matlab
