I am testing a board with an ADC10D1500 and I am getting low values of SINAD for some cases.
I am using a 1.4GHz clock and the Demux-DES mode of the ADCs and I see distortion in the output data that may match with a frequency of ~300KHz. This frequency could be the clock in the switching regulator. I use a LMX25576 followed by a linear regulator (LP38513).
I followed the layout recommendations in ADC datasheet regarding ground a power planes.
Do you think that this clock in the switching regulator can be the root cause of the distorted signal and, hence, low SINAD? If so, any recommendation to erase this effect? Is it more likely to be coupled through the supply or through the ground planes?