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ADS131E04: Externa Reference, buffer resistors R2/R3

Ue
Genius 17165 points
Part Number: ADS131E04

Hi all

My customer is using the ADS131E04 with an external reference and he has this question (referring to Figure 28 in the Datasheet):

When the internal reference-buffer is in shutdown, what happens to  R2/R3?

Is there 50kOhm between VREFP and VREFN  ?

Best regards

Ueli

  • 0
    TI__Guru* 97585 points

    Ueli,



    I'm not entirely sure, but I believe that R2 and R3 are disconnected from the reference inputs when the external reference is enabled. It would be difficult to disable the internal reference buffer without disconnecting the gain setting resistors.

    However, I wanted to check if that was important. When the external reference is enabled, the input impedance looking into the VREFP and VREFN pins is 6kΩ. That is listed in the Electrical Characteristics table under the External Reference. That 6kΩ will be a much larger draw of current from an external reference than the internal reference buffer resistors.



    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Genius 17165 points

    Joseph

    Thank you for the quick reply and understood, makes sense.

    I assume this reply will be ok and sufficient for my customer.

    Best regards

    Ueli