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TMS320F280023: Can the device work if the crystal oscillator (X1/X2) is chosen to 25MHz?

Will Gao
Intellectual 2285 points
Part Number: TMS320F280023

Hi experts, 

My customer makes a mistake: they chosen a crystal oscillator of 25MHz. But from our datasheet: 

The maximum frequency for external crystal oscillator is 20MHz. 

I want to know what will happen if crystal oscillator is 25MHz? Will PLL be fine? Although the SYSCLK and CPUCLK can be set to 100MHz by SW, I want to double confirm the hardware's influence. 

Best Regards, 

Will 

  • +1
    TI__Genius 15385 points

    Hi Will,

    PLL will be fine as long as you are meeting the Internal Clock Frequencies specification (mentioned in the Datasheet).

    You can run the Crystal at 25MHz but that will reduce the negative resistance of the oscillator if the load capacitor selection is not done properly, which will impact the stability and startup time of the crystal oscillator. Customers or their vendors can characterize their setup to see how much negative resistance they have in their system. If it ends up being > 3x ESR, then it’s fine.

    Best Regards,

    Nirav

  • 0 in reply to Nirav Ginwala
    TI__Intellectual 2285 points

    Hi Nirav, 

    Understood, thanks for your guidance. 

    Best Regards, 

    Will