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ADS131E08: Measurement range and performance relative to VREF

Matt Calvo
Genius 13975 points
Part Number: ADS131E08

Tool/software:

Hey Precision ADC Team,

I have a customer evaluating the ADS131E08 for a project and we were hoping you could help to provide guidance on a couple questions related the reference input voltage and overall measurement range. Please see the testing conditions and questions below!

AVDD = DVDD = 3.3V

VREFP = 2.4V, configured as an output

VREFN = AVSS = 0V

VINxP = ranges from 0V to 2.4V

VINxN = 1.2V

PGA gain = 1

Based on the differential input voltage specs in the Recommended Operating Conditions of the datasheet, are we using the full measurement range of the ADC? If we were able to supply 5V to AVDD, would we be able to increase VINxN to 2.4V and VINxP up to a range of 0V - 4.8V? If so, is there any benefit to doing this, instead of just increasing gain to 2?

Best regards,

Matt Calvo

  • 0
    TI__Mastermind 37955 points

    Hi Matt,

    The customer's configuration does not utilize the full scale range of the ADC. The ADS131E08 ADC always measures the differential voltage between VINxP and VINxN which is -1.2V to 1.2V when VINxP is sweeping from 0V to 2.4V and VINxN is 1.2V, but the full scale range is -2.4V to 2.4V when Vref=2.4V.

    Yes, using a 5V AVDD can utilize the full scale range of the ADC when VINxP is sweeping from 0V to 4.8V and VINxN is 2.4V. This requirement depends on the input signal:

    • If the input signal is 0V - 4.8V, you have to use 5V AVDD without signal conditioning circuit to scale it down.
    • If the input signal is 0V - 2.4V and wan to use 3.3V AVDD,  Gain=2 is usually configured and used. The input-referred noise under different Gain configurations will be slightly different at the same output data rate and OSR configuration.

    BR,

    Dale

  • 0 in reply to Dale Li
    TI__Genius 13975 points

    Thanks for the feedback and advice Dale!

    I'll pass this info along to the customer and will have them comment back on here directly with any follow-up questions they may have!

    -Matt

  • 0 in reply to Dale Li
    Prodigy 20 points

    Thank you for the clear and informative answer Dale! We're going to try a 5V AVDD rail for this particular project and see how much of an improvement we can eek out. Many thanks to both of you.