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TMS320F28235: External 20MHz crystal doubt

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Replies: 2

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Part Number: TMS320F28235

Hi,

Customer is using F28235 Q100 for their application. 20MHz external crystal is used.

Here are some doubts:

1) Can 20MHz be used? It should be OK.

2) What's the recommendation for CL and other specifications?

Thanks a lot.

Br, Jordan

  • Jordan,

    The max PLL multipler is 10/2.  You will only be able to achieve 100 MHz operation with a 20 MHz crystal.  You can use 20 MHz with that restriction.

    Normally, people use 30 MHz crystal with F28235 to achieve 150 MHz operation.

    Regards,

    David

    -----------------------------
    David M. Alter
    Senior Member Technical Staff
    Texas Instruments Inc.

  • In reply to David M. Alter:

    The parameters for the passive components vary based on the crystal chosen. Hence we do not recommend any values. Our datasheet has the following note:

    TI recommends that customers have the resonator/crystal vendor characterize the operation of their device with the DSC chip. The resonator/crystal vendor has the equipment and expertise to tune the tank circuit. The vendor can also advise the customer regarding the proper tank component values that will produce proper start-up and stability over the entire operating range.

     

    Hareesh J, C2000 Microcontroller Applications, Texas Instruments.

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