AD7701 self-calibration

Are there any known issues with the AD7701 self-calibration (SC1 & SC2 low) going to the AIN instead of the AGND?

  • 0
    •  Analog Employees 
    on Dec 5, 2016 5:24 PM

    None I am aware of.

    what are you seeing? Did you tie SC1 and SC2 low and performed a self-cal, but the resulting offset value is not correct?

    Ren

  • 0
    •  Analog Employees 
    on Dec 5, 2016 5:58 PM

    Maybe that switch is there for system cal?

    I doubt the part will work at all without the clock...

    I don't know if the part will recover and finish the cal once the clock is back, but I'd try having the clock present at all times.

    Ren

  • 0
    •  Analog Employees 
    on Dec 5, 2016 6:35 PM

    We do try to keep the datasheet revision history on the datasheet. But that practice may have started since early 2000. As you can see they have only captured the last change in page 18 of the datasheet.

    Most datasheet revisions are in fact not caused by errors of the part itself. And for this type of parts, any known errors will either be mentioned on the datasheet or fixed in design, and in the latter case a PCN will be issued.

    the only PCN of this part i can see is related to material change.

    So it's unlikely there's an issue with the self-cal function of the part, but that doesn't mean there isn't some other good reason why that switch is there on your old design.

    Ren

  • In our current design there are provisions with an analog switch tied to AGND external to the ADC until after the self-calibration is complete.  This implies to me that there was an issue at one time that created an issue with the calibration using the AIN instead of AGND internally.

    What are the results if the CAL is attributed and there is no clock present?

    Matt

  • Thanks.  There have never been any provisions/revisions to use anything other than the self-calibrate from the initial design. The clock timing is due to power up issues.  Sometimes the CAL is attributed prior to the clock being there.

    Are there any revisions notes or errata for the AD7701?  The specsheet is on rev e so that would imply some changes, correct?