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  • TI Thinks Resolved

ADS122U04EVM: Too mach noise ADS122U04

Prodigy 20 points

Replies: 2

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Part Number: ADS122U04EVM

Hello!

I bought ADS122U04 Evalution Mode. Installed Delta-Sigma ADC EvaluaTIon Software on my PC.

Set the register values as shown in the attached pictures.

AINP and AINN shorted to (AVDD + AVSS) / 2; Gain 8; 600SPS; Normal mode; Internal 2.048 reference

I get the noise value (uVpp) = 699*0.122 = 85.278 uV

But in the Datasheet this value is 22.30 uV

Why is this happening?     

  • Hi Ivan,

    Welcome to the E2E forum! I think part of the problem is in your calculation. The LSB value is related to full-scale range. Formula 8 on page shows:
    LSB = +/- Vref/Gain/(2^24 - 1) = +/- 2.048/8/(16777215) = 31nV

    31nV * 699 codes p2p equal 21.3uV which matches very close to the datasheet values. This is also verified by the ENOB and NFB values that also match the values in Table 2.

    Best regards,
    Bob B
  • In reply to Bob Benjamin:

    Yes indeed! 
    Thank you very much!

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