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About ENOB and sample rate.

Alan Liu15
Intellectual 270 points

Hi, It's my first time to design ADC converter. I have a few questions. 

1.If the signal that I want to capture is sourced from DC/DC converters, how much the sample rate should be  chosen ?

2.About the ENOB, if I choose a ADC that is 12 bits, and the ENOB is 11.1bits. What does the ENOB means ?  

  • 0
    TI__Guru**** 168605 points
    Hi Alan,

    Welcome to our e2e forum! If you are just trying to measure a static DC voltage, you probably don't need a high sample rate. Generally speaking, whatever the end system or application is determines what the minimum sample rate needs to be. ENOB means Effective Number Of Bits, basically its a measure of the performance of the ADC .
  • 0 in reply to Tom Hendrick
    Intellectual 270 points

    Hi Tom : 

    Thanks for answering. 

    For question 1 :

    If the signal comes from a DC/DC switching converter, the switching frequency is 300KHz, so the output ripple voltage may also has a frequency 300KHz, therefore, the sample rate of my design should be over 300KHz. Is this ideas correct ?

  • 0 in reply to Alan Liu15
    TI__Guru**** 168605 points
    Hi Alan,

    If your objective is to capture and analyze the ripple frequency content of the DC/DC, then you will have to sample at much higher than 300KHz (at least 600KHz). If all you want to do is capture the average DC value on the output, you could probably use a lower sampling rate. If you can provide any detail on what the end goal of your application is, we may be able to recommend a couple different parts to look at.