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ADC12DJ3200: foreground calibration downtime duration

Vincent GLEYZES
Prodigy 50 points
Part Number: ADC12DJ3200

Dear Madam, Sir,

We are using ADC12DJ3200 and would like to know the downtime duration of a foreground calibration (+ offset calibration) of the ADC. The datasheet says:

Foreground calibration always runs on power-up and the user must wait a sufficient time before programming the
device to ensure that the calibration is finished.

Do we have an estimation of this sufficient time to wait ? Is it seconds, hundreds of miliseconds ? For the moment we are waiting for 1 sec and it seems to be enough but we would like to know if this can be shorten for a more userfriendly experience?

Thanks in advance for your answer,

Best regards,

Vincent

  • 0
    TI__Intellectual 1950 points

    HI Vincent,

    The calibration time is strongly dependent on whether any of the default calibration options have changed.

     With default setting on FG and with 3.2Ghz device clock and with the exception of offset calibration being enabled, your wait time is ~200ms. If your clock is running at a lower speed then wait time will be proportionally longer.

     I'd recommend to observe FG_DONE(register 0x6a) signal after triggering the calibration to see how long it actually takes to go high (as measured by your timing reference).  It would be really easy to have some ADC register in a non-default state that causes calibration time to change dramatically.

  • 0 in reply to Miguel Lomeli
    Prodigy 50 points

    Hi Miguel,

    Thank you for your answer.

    I don't look continuously at FG_DONE because I thought that issuing SPI command during calibration could interfere with the calibration. I thought that's why the datasheet indicates that the user must wait a sufficient time before programming.

    If you confirm that I can do a while loop on FG_DONE register then I will be sure to have calibrated in the shortest time possible. If it's not possible I wcan still sleep my program for around 400ms in order to have faster response time and have some margin on the ~200ms you indicated me.

    Regards,

    Vincent

  • 0 in reply to Vincent GLEYZES
    TI__Intellectual 1950 points

    HI Vincent,

    FG_DONE is a status register bit for when foreground calibration is done, a while loop on FG_DONE is ok.