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Relationship between ADC Resolution and VREF

Question asked by bellkev on Aug 30, 2013
Latest reply on Aug 30, 2013 by jcolao

Hello,

 

I have a general question about how Sigma-Delta ADCs operate, or for that matter if any ADC architecture operates how i describe below:

 

If i have a 16bit ADC for example and it has an external reference voltage applied to it, does the full 16bit resolution fit within the reference voltage or is it 16 bits over the supply voltage? Or in other words, a 16 bit ADC should have 65536 steps in voltage that it can measure. If i use a 2.5V reference does that means each step is then 38uV? and if i were to change Vref to something lower would that then decrease the step size?

 

I have an application where i'd like to measure voltage drop across a resistor in a range between tens of microVolts and hundreds of millivolts. Wondering if i can adjust the accuracy of the ADC by changing the reference voltage, or if Analog has something that will already support that.

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