For precision ADCs like the AD7274 the converter noise tends to be dominated by KT/C versus the input resistance of the ADC. The easiest method I've found to estimate NSD is to use the transition noise plot (Figure 22) which shows a histogram…
Are there any power sequencing requirements for VDD relative to VREF on AD7273/AD7274?
On the AD7274's datasheet , for package TSOT, AGND is on pin number 8 and DGND is on pin number 3.
On the evaluation board of this device, regarding the routing layers, it seems to be the opposite (AGND on 3 and DGND on 8) (document attached…
I have attached a list of some of the ADCs that fit your criteria of 2MSPS sampling rate or higher at resolution of 12bits or more.
You may also wanted to check the ADI website and do a parametric search (http://www.analog.com/ps/psthandler…
You may want to check the ADI website and do a parametric search to filter the product display base form your recommended specification.
Here are some ADCs that might help you start with, kindly see attched file.
Here are some list of ADC that could be suitable for your application. You may also wanted to check the ADI website and do a parametric search and put in parameters on the ADC that you wanted to search. Please refer to the link below.