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ADS7142-Q1: how to choose reference voltage?

Sherry Liang
Genius 10255 points
Part Number: ADS7142-Q1
Other Parts Discussed in Thread: REF5050

Dear team,

I noticed AVDD also acts as reference voltage. If we use DCDC to power AVDD, the output accuracy is not good. Do I need to connect this pin to a shunt regulator directly instead of a DCDC?

Thanks & Best Regards,

Sherry

  • +1
    TI__Guru 62765 points

    Hi Sherry,

    You're correct that the ADS7142-Q1 uses the AVDD input voltage as the reference voltage for the ADC.  Therefore, there is effectively no PSSR between the AVDD input and the resulting output codes.  If it's challenging to keep the supply noise to <1/2 LSB for the selected supply range then it's recommended to add an additional LDO or shunt reference to clean up the DC/DC output before feeding to the ADC.

  • 0
    TI__Genius 10255 points

    Hi Collin,

    Got it! Thanks for your reply! 

    I notice our devices have two types, one type uses AVDD as the reference, and the other type has REF pin(internal or external) which is independent of AVDD power.

    In my understanding, with additional REF pin will be more flexible. You can choose a different reference voltage from AVDD. Is there any benefits using the type one, AVDD acts as reference?

    Thanks & Best Regards,

    Sherry

  • 0 in reply to Sherry Liang
    TI__Guru 62765 points

    Hi Sherry,

    Higher performance devices (16-bits and up) typically have dedicated reference pins and are anticipating the use of a dedicated reference, e.g. REF5050, to supply a precision reference voltage outside of the AVDD power-supply voltage.