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TMS320F28379S: tolerance on Ext Crystal stability?

AnBer
Mastermind 30615 points

Part Number: TMS320F28379S

Team,

The F28379S datasheet SPRS881J gives in section 7.9.3.2.1.1 page 63 the min/max crystal frequency that can be used.
Also X1 timing requirements in table 7.9.3.2.1.2 and 7.9.3.2.1.3 are all met.

What is the tolerance required on the crystal frequency? Can the frequency deviate by 1 or 5 percent over time?
Will the device still operate safely if the frequency deviates 5 percent overtime?

In this particular use case the crystal used is 20Mhz and the SYSCLK from PLL is 200MHz.
For this configuration do you foresee issues due to crystal tolerances?

Thanks in advance,

A.

  • 0
    TI__Guru* 95315 points

    An,

        The tolerance you quote is not realistic for a crystal . A review online for 10MHz to 20MHz crystals shows the max PPM to be 180 PPM, which is equivalent to 0.018%. Typical crystals are much less than 50ppm worst case. As long as the design uses these crystals, these negligible excursions over the max frequency limit is OK.