ADC Design Help [closed]

Question

I am planning to design a new ADC but I have not designed an ADC before. I will read at 10uV level. I am thinking of using a high resolution ADC, and also MCU I am open to suggestions on this subject. If you share the appropriate document, I will review it.

Answer 1

Reading at 10 µV will be challenging. Just having a lot of bits will not help. It is very imporntant that front end before the ADC is done in a way that the noise in your region of measurement is bellow what you are trying to measure. For the values that you are mentioning it would be useful to use differential input into ADC. Also you need to make sure that power supply and voltage reference for ADC are very clean (don't have a lot of noise). Futher more, for precision measurement you also need to make sure that digital parts of your circuit which typically have sharp rise/fall times don't create EMI, meaning you need to make sure that your ADC won't sample some disturbances caused by your digital part.

When designing any type of digital acquisition the following points need to be considered first:

1. Voltage range that you are trying to measure
2. Required precision (I think you defined that with 10 µV)
3. Required accuracy (not the same as precision, a lot of times not needed, but sometimes very important, depends on the application). This will be important when picking voltage reference. Also, long term stability can also be important
4. What kind of signal are you trying to measure, the impendance, etc.
5. Bandwidth required
6. Limitations on digital interfaces (you can't use very fast interfaces with microcontrollers, you might need an FPGA)
7. Limits on power consumption
8. Is it required that ADC reads continuously or can it read only on request

From this points you can conclude what DNL and INL you need, how many bits are required, and how low does the noise of the front end need to be and how does it need to be implemented. ADS1220 and related family could be useful, but are not the only components available.