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AM6442: PCIE REF CLOCK

AMARNATH G
Intellectual 255 points

Part Number: AM6442
Other Parts Discussed in Thread: LMK00334

Dear TI,

We are designing the PCIe based NIC card. In this design we are planning to use 2No's of AM6442 as the PCIe End Point. 

Now to provide the PCIe Ref Clock (HCSL Clock output type) we are planning to use LMK00334 as the PCIe Ref Clock buffer. Here in the LMK00334 TI datasheet, it is stated that the output supply voltage VCCOA & VCCOB ranges from 2.5V or 3.3V, while the AM6442 SerDes REFCLK I/O operating voltage is 1.8 V.

Considering the above point, can you please confirm us if we can go with LMK00334 as PCIe Ref Clock Buffer to provide HCSL Clock input to AM6442 PCIe Ref Clock?

Thank you.

  • 0
    Intellectual 255 points

    Dear TI,

    can we please get an update on the above query.

    Thank you.

  • 0 in reply to AMARNATH G
    Intellectual 255 points

    Dear TI,

    Can we please get an update for this ticket, its in a critical path for us now. Request you to provide us your thoughts on this ASAP.

    Thank you.

  • 0 in reply to AMARNATH G
    TI__Expert 6465 points

    Greetings Amarnath,

    It's hard to understand the basis of your question. The supply voltages are different, but I'm thinking you're asking about the reference clock output correct? These are two separate things.

    The output characteristics of the LMK00334 HCSL differential output are on page 6 and page 7, these would be what to consider for clock compatibility for feeding a clock into the SoC. On a quick inspection it appears to be PCIe compliant; makes sense, this clock buffer is also specifically targeted for PCIe® Gen 1 to Gen 7 applications. As long as the reference clock is PCIe compliant it will work for our SoC.

    Sincerely,

    Lucas

  • 0 in reply to Lucas Bowe
    Intellectual 255 points

    Hi Lucas,

    Thanks for your response.

    Yes, exactly that was what I was asking for.

    Since the output characteristic of LMK00334 HCSL differential output are on page no:7 of datasheet which mentions the voltage swing as 520mV (Min) to 920mV (Max).

    In this case, we can connect the outputs clocks directly to the 3 devices (The devices are 2x AM6442 and 1 x PCI12000), without any voltage divider or any discrete output terminations, correct?

    Since LMK00334 is specifically targeted for PCIe Gen 1 to Gen7 applications and AM6442 and PCI12000 are also PCIe compliant, LMK00334 should work for our AM6442 and PCI12000 devices without any voltage divider or any discrete output terminations, is my understanding correct?

    Thank you.

  • 0 in reply to AMARNATH G
    TI__Expert 6465 points

    Greetings Amarnath,

    If everything is PCIe compliant it should be fine. As always, be sure to fully read the clock buffer's documentation for any requirements that need to be incorporated into your design. For example section 8.2.2 Detailed Design Procedure details termination requirements for the output signal.

    Sincerely,

    Lucas