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DRA821U: PCIe refclock sourced by processor?

Steve Turza
Intellectual 280 points
Part Number: DRA821U
Other Parts Discussed in Thread: DRA821, LMKDB1102

Tool/software:

We are designing a product using the DRA821U processor using PCIe.
I have seen conflicting information regarding the use of the PCIe refclock sourced by the processor.
I have read the Errata, and I would like some assurance that source mode is supported.

Thanks,
Steve

  • 0
    TI__Guru 53123 points

    Hi Steve,

    Currently, the SDK does not support outputting a PCIe refclk from processor specifically for DRA821 in the Jacinto family due to changes with ACSPCIe clock buffer. 

    If you have not designed the board yet, then I would recommend using an external clock generator to source the refclk. This will work around the erratas and lack of software support.

    Regards,

    Takuma

  • 0 in reply to Takuma Fujiwara
    Intellectual 280 points

    Thanks Takuma,

    I have re-designed my schematic to use the LMKDB1102.

    Can you please confirm that this part will provide an adequate PCIe refclock, my concern being that this part is "LP-HCSL" output strength.

    Thanks,

    Steve

  • 0 in reply to Steve Turza
    TI__Guru 53085 points

    LP-HCSL is OK as long as it meets the PCIe Refclk specifications. Also, unlike HCSL, LP-HCSL integrates the termination resistors into the buffer so that they are not required to be placed on the PCB.