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ADS7861: capacitance on reference output pin

Andreas Breu
Prodigy 20 points
Part Number: ADS7861
Other Parts Discussed in Thread: TLV9152

Tool/software:

Good Day!

What is the correct capacitance to ad on REFout pin for the ADS7861?

In the datasheet (SBAS110D) page 8: "(the internal reference can typically source 2mA of current load—capacitance should not exceed 100pF)"

But in the EMC User's Guide (SLAU094A) on page 7 in the schematic a 470nF is connected to the REFout pin.

That's why I'm asking this question. Also, we are using the ADS7861 in an older design (in single-ended configuration -> REFout, REFin and the negative channels are connected) with a 100nF, which works fine.

Kind regards

  • 0
    TI__Intellectual 1660 points

    Hello Andreas! 

    Thank you for posting on our forum! 

    Like your previous application and the EVM, 100nF is recommended and even a larger capacitance should work (this can be found in the Layout section of the datasheet), when either there is an external reference connected to REFin or when REFout and REFin are shorted together.  

    The section you are referring to where the load should not surpass the 100pF is when the internal reference is being used to drive an external load . In this case the REFout has the capability to drive 2mA as long as the load capacitance does not exceed 100pF. 

    In your design, do you plan to use the ADS7861's internal reference to drive anything external to the ADC? 

    Please let me know if I could help with anything else! 

    Best regards, 

    Yolanda

  • 0 in reply to Yolanda Gonzalez
    Prodigy 20 points

    Hello Yolanda

    I would like to connect the reference output with a voltage divider (10k and 4.7k) to a buffer (TLV9152) to generate a reference voltage of approx. 0.8V.
    With these values, the current load of the REFout is not overloaded. (0.17mA)
    Which bypass capacitance would you recommend in this case?

    Best regards,

    Andreas