ADS8353: ADS8353

Hello Jake, 

Welcome to TI's E2E forum! Thank you for posting your question. 

This e-book, Fundamentals of Precision ADC Noise Analysis, covers a lot of useful information about ADC noise along with the full series of ADC noise that the video you are referencing to (Calculating the total noise for ADC systems) in the picture you shared. I invite you to go through the document and watch the full series of ADC noise in the Precision Labs Videos.

Both of those resources should help understand the difference between AC and DC noise measurements as well as how determining the total noise of the ADC is dependent on multiple variables. They should be able to to answer your question as well as help understand the subject more clearly

In the specific video you are referencing, it is going through an example case of calculating noise when more than the ADC is present, this was part of a Hands-on experiment to showcase the ADC noise. This was not only to show the ADC noise calculation in a system with an OpAmp and an external reference but to show the effects of thermal noise.  For this experiment since the thermal noise provided by the OpAmp w/gain was larger than the noise of the ADC, using the SNR to calculate the noise was enough for simulation purposes. 

But you are correct, in a system where there is a DC input, the DC noise of the ADC would be the ideal value to use, and in systems with AC inputs AC noise should be considered.  How to make these calculations and measurements as well as how to determine which methods/values are more relevant depending on the use case, resolution, and other variables are covered in more detail in the links provided. 

Best regards, 

Yolanda

Hello, 

My question is that why do they use RMS value from SNR of ADC even though input is DC input.