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TMS320F28335: External reference quartz crystal

LE QUERRIOU STEPHANE
Intellectual 280 points
Part Number: TMS320F28335
Other Parts Discussed in Thread: C2000WARE

Dear,

We use TMS320F28335PTPS with external quartz oscillator.

We have  troubleshooting with PLL stability.

Quartz used is -40 to 125°C range, reference is 520-ECS-300-18-33QS (ECS INC), we add CL1 and CL2 (capacities load) as 18pF.

Could you tell us if these components are compatibles with DSP clocking?

Regards

  • 0
    TI__Expert 8105 points

    Stephanie,


    What kind of PLL stability issues are you seeing? What is the temperature at which these tests are done?


    Regards,
    PETer

  • 0 in reply to Peter Galicki
    Intellectual 280 points

    Dear Peter,

    Tests are done at 30°C ambiant temperature.

    We have some troubleshooting with initialization code:

    do

            {

                /* Check the PLL lock bit */

                if (((SysCtrlRegs.pllsts & PLLSTS_PLLLOCKS)== eINT_ZERO))

                {

                    bWaitPLLLockBitToBeSet = FALSE;

                }

                else

                {

                    bWaitPLLLockBitToBeSet = TRUE;

                }

                /* Is the PLL lock bit is set */

            }

            while (FALSE == bWaitPLLLockBitToBeSet);

    Then we add this line (from TI documents):

    HAL_BOOT_WaitLoopNonoSecond(500000.0);

    After that, program work better but we have hazardous behavior of others functions like SPI, EMIF,...

    These functions are clocked with the same clock, then we think about quartz loop phase stability.

    Could you tell us if added capacitors around quartz have correct values? (18pF)

    Regards

  • 0 in reply to LE QUERRIOU STEPHANE
    TI__Guru* 95315 points

    I regret I am unable to understand exactly what the problem is; "hazardous behavior of others functions like SPI, EMIF" does not say much. Exactly what is happening with those peripherals? Here are some suggestions questions:

     

    • Are you able to run a C2000ware example "as is"? For example, can you run the SPI example in the C:\ti\c2000\C2000Ware_1_00_05_00\device_support\f2833x\examples directory? The idea is to eliminate any issue with your software.
    • If you run the device at a lower speed, say 75 MHz, do you still see the issue?
    • Assuming it is possible with your current board layout, is it possible to feed a 30 MHz clock directly into the XCLKIN pin and see if it makes a difference?
    • Have you measured the actual clock frequency at the XCLKOUT pin to convince yourself that the device is indeed running at the clock speed you are expecting it to?
    • Have you ensured correct wait-states for flash?