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TMS320F2800137: Internal oscillator accuracy

Nicolas UHL
Prodigy 100 points
Part Number: TMS320F2800137


Tool/software:

Hello,

I'm developping an application for a power electronics product on a TMS320F2800137.

I'm using the internal oscillator to run at 120MHz.

So my PWMs timers and sampling frequency are based on this internal oscillator.

I observed (on several samples) that the frequency is higher than the theoretical value by more than +1.5%

The datasheet specifies -1.8% / +1% 

So it seems it is out of spec.

Is there a way to calibrate the oscillator ?

What is the frequency drift with temperature ?

I developped application on the TMS320F2802x and F2803x and there was an oscillator calibration / compensation mechanism.

Is is available on the new TMS320F280013x ?

Thanks in advance.

Best regards

Nicolas Uhl

  • 0
    TI__Mastermind 39170 points

    Hi Uhl,

    The internal oscillator circuits for the F2800137 and the F2802x/3x are very different.  The F2802x/3x have linear frequency response with temperature so it more straightforward to calibrate.  The F2800137 internal oscillator circuit has a 2nd order frequency vs temp relationship, making temperature calibration difficult.  PWM timings in power electronics is critical for syncing with grid or driving IGBTs so using the internal oscillator is not recommended.  An external clock/crystal is best suited for such applications to clock the F2800137 part.

    Regards,

    Joseph