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ADS131M08: Vref

wei yufeng
Prodigy 110 points
Part Number: ADS131M08

Tool/software:

hello TI experts，

Question 1:  if configuring bit 6 of CLOCK Register to 1 will physically disconnect the 1.2V internal reference within the ADS131M08 chip (through a switch like mechanism)?

Question 2:  According to the data manual, when using an external reference of 1.25V, the actual ADC full-scale range is 1.2V/gain PGA; But the reference voltage of 1.3V is 1.248V/gain PGA. May I ask how 1.25V corresponds to 1.2V/gain and 1.3V corresponds to 1.248V/gain, which are not described in the manual.

      

  • +1
    TI__Mastermind 39985 points

    Hi wei yufeng,

    Please see the answers below.

    1. Yes, it will disconnect the internal voltage reference if bit 6 in CLOCK Register is set to 1.

    2. For ADS131M08, the full-scale ADC code is with respect to 1.2V using the internal VREF and with respect to 0.96*VREF using external reference. 

        For example, if you are using

    • a 1.25 V external reference, then a differential input voltage of 1.2V on the ADC input will give you a positive full-scale code when the gain is 1.
    • a 1.3 V external reference, then a differential input voltage of 1.248V on the ADC input will give you a positive full-scale code when the gain is 1.

    Regards,

    Dale

  • +1 in reply to Dale Li
    Prodigy 110 points

    Thank you for your reply.