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LMK03318: propagation delay parameter

Amy Luo
Expert 6895 points
Part Number: LMK03318
Other Parts Discussed in Thread: CDCM6208, LMK04828, LMK04832

Hi team,

Customers need to know what the maximum and minimum t (prop) of lmk03318 is, and how to find this parameter of other similar clock chips.Because I've seen a lot of these clock chips and some of them have not marked the t (prop) parameter,such as lmk041xx series and CDCM6208.

In addition to lmk03318, can the parameters of lmk041xx series and CDCM6208 be provided?

Best Regards,

Amy

  • 0
    TI__Mastermind 18070 points

    Hi Amy,

    It will require additional validation/design effort to provide this information. I'd like to understand what their application is and why they need this spec. Because if they need deterministic delay they can use JESD204B in LMK04828/LMK04832 instead. 

    If the customers do not want to disclose their application in public forum, please submit a "helpme" ticket instead.

    Regards,
    Hao

  • 0 in reply to Hao Z
    TI__Expert 6895 points

    Hi Hao,

    Thank you very much for your reply.

    Customers need to synchronize between multiple PCB boards. Each PCB board will have such a clock chip. There is an external clock signal with a very small skew input to this clock chip on each PCB board. Customers are concerned that if the t(prop) parameters of clock chips vary too much between devices, additional skew will be introduced into the subsequent working clocks.

    Best Regards,
    Amy

  • 0 in reply to Amy Luo
    TI__Mastermind 18070 points

    I see. Unfortunately, the 1ns that you pointed out in the original post is NOT prop delay between input and output under normal operation, because the test condition says "PLL bypass". Meaning that this is the delay when the output is buffered input.

    Under normal operation, prop delay can vary when register settings are changed, that's why we didn't specify prop delay with PLL enabled.

    In general, I don't recommend relying on the prop delay of devices to get synchronization, because the delay can vary with temperature and process. Like I said in the previous post, this is commonly done using JESD204B. You can refer to LMK04828 or LMK04832 datasheet and appnotes for more details.

    Regards,

    Hao