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TMS320F28033: Oscillator Compensation

xiaolin lu
Prodigy 20 points
Part Number: TMS320F28033

hello:

     There is a register INTOSCnTRIM for internal clock calibration. The range of FINETRIM is -31 to 31. Is the value from -31 to 31 directly added to 10M? 

 

  • 0
    Prodigy 20 points

    We want to know how this coarse and fine adjustment value is applied to the 10M crystal oscillator?

  • 0 in reply to xiaolin lu
    TI__Guru 71785 points

    Xiaolin,

    This is correct, any change in the fine trim will move the internal 0 pin oscillator according to the DS TYP which is ~14kHz for each step.

    Please keep in mind that this is signed magnitude format and not 2's complement so any register view in CCS will not show the negative value correctly.

    FINETRIM register is used by the oscillator temperature compensation function to re-center the frequency based on measurement by the temp sensor.

    Note that each device is trimmed from the factory to be ideally 10MHz at 30degC, so the value after device_cal function of both coarse and fine trim will be non-zero.  It should be possible to realize ~10MHz across the temp range of the device by only modulating FINETRIM only.

    Best,

    Matthew