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TMS320F28023: How to evaluate the delay time while using external crystal(X1/X2) while doing XtalOscSel()

Benjamin Zhou
Expert 4000 points
Part Number: TMS320F28023

Hi Team,

   My customer used F28023, and now reported an issue that the device couldn't run while using external crystal(X1/X2 Pin),  while increased the delay time in XtalOscSel() prototype, the F28023 could run, decreased the delay in XtalOscSel() prototype, the F28023 couldn't run. 

   Could you kindly give comments on how to evaluate the delay time in XtalOscSel() prototype?  Expect for your kindly reply, thanks.

   More details could be found in attached file. F28023 Clock Failure Issue.pptx 

Best Regards
Benjamin

  • 0
    TI__Guru* 95315 points

    Benjamin,

    Crystal oscillator startup time is dependent on many parameters: The crystal itself, the load caps and other parasitics of the oscillator circuit. Have you measured the startup time with an oscilloscope. It is important to use an active FET probe with <2 pF capacitance. Otherwise, the very act of connecting a scope probe would alter the oscillator behavior.