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TMS320F28027F: Internal Zero-Pin INTOSC1/INTOSC2 Oscillator Accuracy and resulting PLL Accuracy..

Newman
Expert 5995 points
Part Number: TMS320F28027F

Hi Team C2000,

The only reference I can find for the accuracy of the TMS320F28027F internal Zero-Pin Oscillator INTOSC1/INTOSC2 and resulting PLL Clock Accuracy.. is in the datasheet fig 8-8 which is a chart of "Zero-Pin Oscillator Freq Movement w/ Temperature".. am I missing the spec of the overall INTOSC1/2 accuracy?

Thanks, Merril

Ref:

https://www.ti.com/lit/ug/sprui09/sprui09.pdf

https://www.ti.com/lit/er/sprz292s/sprz292s.pdf

https://www.ti.com/lit/ds/symlink/tms320f28027f.pdf

https://e2e.ti.com/support/microcontrollers/c2000/f/c2000-microcontrollers-forum/417790/for-tms320f28027-i-need-to-connect-external-crystal-oscillator

  • 0
    Guru 92251 points

    Since the datasheet defines the Step size (fine trim) as 14 kHz (typ), does it mean that if the software implements the Oscillator Compensation Guide, and VREG is enabled, that can get the INTOSC1/INTOSC2 frequency to 10.0 MHz ± 14 kHz?

    However, since the following datasheet parameters have only typical values difficult to quantify the absolute accuracy than can be achieved by adjusting the fine trim according to the temperature:

    • Internal zero-pin oscillator 1 (INTOSC1) frequency
    • Internal zero-pin oscillator 2 (INTOSC2) frequency
    • Step size (coarse trim)
    • Step size (fine trim)
  • 0 in reply to Chester Gillon
    TI__Guru* 80080 points

    I need to look into this a bit more.  There is some inference we intend to make from the graph, wrt the max plot, that is the variance should be 9.65MHz to 10.45MHz.  At any rate the device will work correctly even with PLL x6, even if the frequency is >60MHz.  We test the device using the internal oscillator at its max condition to verify operation.  The ideal of 10MHz is centered at ~37C and that temperature should serve as the center point for any temp movement.

    The calibration is a bit of a different matter.  While the resolution of the trim steps in neighborhood of 14kHz; the issue is the transfer function of the oscillator over temperature is not ideal/linear. 

    The calibration routines, for simplicity, assume this to when they read the temp sensor and re-trim the oscillator The re-calibration(vs the static factory value that gives the +/-4.5% above) will be better, probably on the order of a couple of % points depending on the temperature.

    Best,

    Matthew