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LMK00334-Q1: Recommended CLKin Termination for LP-HCSL PCIe Gen 5

Antonio Fadhel
Genius 9410 points
Part Number: LMK00334-Q1

Hi Team,

Can you please share the recommended LMK00334-Q1 CLKin termination components for a LP-HCSL PCIe Gen5 input clock?

Thanks,

Antonio

  • +1
    TI__Mastermind 28530 points

    Hello Antonio,

    LP-HCSL is a source terminated driver.  So typically the driver will need series resistance at the source in both the inverting and non-inverting output to absorb the reflection from the load.  The resistance at the source will depend if you are doing an 85-ohm or 100-ohm system but will generally result in a sum of 85 ohms / 2 or 100-ohms / 2.  The actual resistance may vary based on the specs of the LP-HCSL driver.  For instance, some drivers may have the source termination integrated.

    73,
    Timothy

  • 0 in reply to Timothy T
    TI__Genius 9410 points

    Thanks, Timothy! For the LMK00334-Q1 HCSL outputs, if the differential trace impedance is 85ohm on the receiver side, should the termination resistors still be 50-ohm? I would assume so since it is a current-based topology but just want to confirm if it would be an issue with reflection from the load.

    Regards,
    Antonio

  • +1 in reply to Antonio Fadhel
    TI__Genius 10125 points

    Hi Antonio,

    In the case of 85 ohm differential impedance, the 50 ohms to ground termination is still required and the Rs would be 27 ohms. 

    Regards,

    Jennifer