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External device clocking using 28069F PWM output

Mojo
Expert 1570 points

Hi,

I'm using the 28069F.

I have an external device that needs a 4MHz clock, so I thought to use one of the 28069F PWM outputs.

The external device manufacturer states that the clock should be with a tolerance of maximum 200PPM.

I looked in the 28069F but couldn't find such a parameter. I'm using the internal oscillator for the 28069F.

Can I achieve 4MHz with 200PPM using the internal oscillator of the 28069F ?

Thanks a lot

  • 0
    TI__Guru 57255 points

    Hi Mojo,

    If you take a look at the F2806x device datasheet, you'll find the tolerance of the internal oscillator.  Once you do so, you'll see that the tolerance is around 1% when compensation is done.  1% equals 10000ppm.  From 10MHz to 4MHz, there's a factor of 2.5.  I'd estimate that you could get a PWM output of ~4000ppm with the internal oscillator, based on the electrical specs within the F2806x device datasheet.

    If an adequately precise external crystal was used to clock the F2806x instead, I think generating a PWM/clock that meets your external device's specification would be feasible.


    Thank you,
    Brett