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BQ32000: RTC Calibration question

Russ Chen
Prodigy 165 points
Part Number: BQ32000

Hi, there,

'Cause we're requested to have +/1ppm accuracy of RTC by customer.

And the minimum tolerance of 32.768KHz crystal is +/-5ppm. 

We'd like to confirm the 'Calibration' function on BQ32000.

There're options to select in the register.

If we select -4ppm, does that mean original +/-5ppm will be calibrated to +1ppm, -9ppm? Or both calibrated to 1ppm?

Please help to clarify our confusions.

Thanks in advance.

Regards.

Russ

  • 0
    TI__Genius 16845 points

    Hi Russ,

    Q:If we select -4ppm, does that mean original +/-5ppm will be calibrated to +1ppm, -9ppm? Or both calibrated to 1ppm?

    A: The +/- 5ppm accuracy specified in the XTAL datasheet means that the accuracy of the XTAL will be 32.768kHz XTAL will be guaranteed between 32.768kHz - 5ppm and 32.768kHz +5ppm. Therefore, if you select -4ppm for an XTAL with +/-5ppm range, the range is now +1ppm to -9ppm. Note that the calibration effect is only observed every eight to sixteen minutes

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    Prodigy 165 points

    Hi, Lane,

    Good day.

    Thank you for your reply.

    Regards.

    Russ