# How to find the right (external) ADC for an Arduino project?

there is a specific project I am trying to tackle using an Arduino, but I'm fairly new to this topic, which is why I would appreciate your help on choosing the right components and overall circuit.

I want to digitalize an analog signal with the following constraints:

-> voltage range of the signal: 0 - 4 V
-> desired precision/resolution: 0.1 mV


From those two parameters, I conclude for the ENOB (x being the minimal ENOB I need):

- 2^x = max. voltage range  /  voltage resolution
- 2^x = 4V / 0.1 mV
----> x = ENOB = 15.288    (please correct me, if there is something wrong with that)


The signals coming in have a length of around 50 microsecs, given that I want to reconstruct them as well as possible, I am aiming for:

sampling rate: 40 megasamples / sec (--> every 25 ns if I am not completely wrong :D) (I am aware that this is much of a constraint, if you say it is too high of a goal, what do you consider a doable sampling rate?)

Therefore, summing up what I am looking for, I would need an ADC with:

---> ENOB >= 15.288 Byte
---> sampling rate 40 MSPS


Now I am pretty sure the internal ADC of an Arduino can't do that which is why I am trying to find an external ADC to connect to it, so I can use the Arduino mainly to run some other code with the data without being limited by its ADC's capabilities. On that topic the following question arises:

• Are there chips meeting all those constraints? (Of course, I am also searching but I thought I'll just pop the question, maybe some of you know something right away :))

Otherwise, here are my questions / insecurities:

• Is the stuff (calculations, thoughts, ...) I showed by now right / reasonable?
• Is there anything else (other characteristics etc.) I should pay more attention to when choosing the ADC?
• Can you recommend a specific tutorial (I saw a few that I could post the links for, but maybe the specialists among you consider a specific one especially nice) on how to make the ADC - Arduino connection work properly?