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Original question:

ADS1256: Please check my 2.5V VREF and 5.0V circuit, Thanks.

ADS1256: What's the relationship between AVDD and VREF?

YC Hsu
Prodigy 60 points
Part Number: ADS1256

There's 3 type of voltage in ADS1256 : DVDD, AVDD, VREF, 

As Topic,

After read the datasheet of ADS1256, I still can't realize the relationship between AVDD and VREF.

Can someone explain to me how this ADC works?

  • 0
    TI__Guru 52226 points

    Hi YC Hsu,

    The ADS1256 datasheet does a very good job of explaining how the ADS1256 works. Please review that document in detail and then ask specific questions.

    What do you mean by "relationship between AVDD and VREF"? What information exactly are you looking for?

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 60 points

    I just can't realize how does these voltage work,

    Generally speaking, VREF is the voltage used as a reference,
    So what is the role of AVDD?
    In other words, why does the value of AVDD affect the ADC conversion result?

  • 0 in reply to YC Hsu
    TI__Guru 52226 points

    Hi YC Hsu,

    You are correct that the VREF voltage is used as the reference voltage, so it is very important that this you use a high-accuracy, low noise reference voltage to get the best performance out of the ADC

    AVDD powers the ADC core and other components e.g. the buffer, PGA, etc. This should still be low noise, but it is less critical than the reference voltage. Both the LDO you use to power the ADC, and the ADC itself, have some specified PSRR that will reject noise/ripple at the LDO input from reaching the internal ADC circuitry.

    -Bryan