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ADS114S08B: About measurement range when 2.5V internal reference is used

Junya Kato
Expert 1635 points
Part Number: ADS114S08B


Hello Team,

Can I use a 2.5V internal reference when measuring single ended signal that can swing between 0V and 3.3V?
Do I need to use external reference of 3.3V or more?
By the way, AVDD uses 3.3V.

Best regards,
Kato

  • 0
    TI__Guru** 113765 points
    Hi Kato,

    You could use the internal reference along with a level shift to set AINN as mid-AVDD (1.65V) to make a pseudo differential measurement. You would then need to make a calculation relative to this voltage. The full-scale range in this case is +/-2.5V and an input range of +/-1.65V requiring the addition of 1.65V to every measurement to get the correct result. The issue with this type of measurement is in the stability of the 1.65V connected to AINN and the additional calculation required.

    I think it would be much easier to use AVDD as the reference. With 3.3V as the reference you only use the positive half of the full-scale range (+/-3.3V) so no additional calculations are necessary. The benefit of this measurement is in the simplicity. The issue with this measurement is the reduced measurement range relative to full-scale range (1/2 of the FSR).

    Best regards,
    Bob B