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TMS320F28377S: Crystal parameters recommended in datasheet versus crystals used in Reference Board

Adam Showalter
Prodigy 20 points
Part Number: TMS320F28377S
Other Parts Discussed in Thread: CONTROLSUITE

I'm unable to make sense of this.

Page 64 of the DS says load capacitance (CL1, CL2) must be 12 to 24pF.

Reading this literally, the recommended crystal load capacitance would be somewhere between 6 to 12pF, ignoring parasitics.

The crystal Q1 used in the LaunchPad (LAUNCHXL-F28377S) is as follows:

Mfg PN: ATS100B-E

Description: 10Mhz, +/-30ppm, 18pF, 60 Ohm, -40 to 85C

And of course, the dual load capacitors (C3, C4) used here are both 36pF correctly matching the 18pF load Capacitance of the crystal.

Is this crystal a bad choice or am I missing something? Are there any other recommended crystals?

Thanks - Adam

  • 0
    TI__Expert 7885 points
    Hello Adam,

    The datasheet should be followed. Note that this was probably a xtal which was carried forward from an earlier design and there were no issues seen so the developer of the launchpad kept it. I will discuss the xtal selection with the owner of the launcpad and look at updating accordingly.

    We do not recommend any crystals explicitly as we do not manufacture xtals and cannot guarantee another manufacturers performance. We can only offer the specs of the required xtals.

    You can also have a look at the F28377D controlCARD (from controlSUITE) to see what was used there.

    Best Regards,
    Adam Dunhoft
  • 0 in reply to Adam Dunhoft
    Prodigy 20 points

    Hi Adam D,

    Thanks for the response. The crystal used in the controlCARD looks better so I found something similar. Thank you for pointing me in the right direction.

    Regards,

    Adam S