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BQ32000 Using a different crystal

Victhor Foster
Prodigy 60 points
Other Parts Discussed in Thread: BQ32000

I am having difficulties sourcing a crystal with 12 pF load capacitance, including the reference KDS DMX-26S crystal. I would like to use either a 6 pF or a 12.5 pF crystal, are there any means to correct this difference in load capacitance with extra passive components on the crystal circuit? I suppose it is possible to use the calibration feature of the BQ32000 RTC to compensate for the clock slow down or speed up, but I'd like to know if it can be done in hardware as well.

  • 0
    TI__Prodigy 435 points

    I assigned the thread and you should get an answer soon.

    Best regards,

    Alex

     

  • 0
    TI__Guru 55605 points

    Regarding bq32000, 12.5pf crystal is OK.

     

    6pf crystal is not acceptable.  The internal clock correction can be used to attempt to correct for the mismatch, but the results will not be within the datasheet specs.  The mismatch will cause the oscillator to operate very far away from the high Q point meaning that it will be unstable with temp and voltage.  The oscillator may not reliably start with all 6pf crystals.

     

    Finally, there is no change that can be made outside the part to run a 6pf crystal with an RTC designed for 12.5pf crystals.  Therefore, please select the 12.5pF option.