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LMK00308: Termination circuit when inputting LVDS CLK

Ryotaro Fukui
Intellectual 2345 points
Part Number: LMK00308


Hello team,

My customer has a question about termination and coupling of LMK00308.

When inputting 100MHz CLK from the LVDS oscillator to the LMK00308, please tell me how to configure the circuit such as termination and coupling between them.

They would like to confirm the following data sheet because it seems that there is only an  example of inputting a single-ended signal and a crystal to the LMK in the application example.

https://www.tij.co.jp/jp/lit/ds/symlink/lmk00308.pdf

Best Regards,

Ryotaro Fukui

  • 0
    TI__Expert 8605 points

    Hello Ryotaro,

    The termination for a DC-coupled LVDS input requires a 100 ohm resistor across CLKinX and CLKinX*.

    The termination is the same for both an LVDS input and LVDS output, so the image below (image of an LVDS output termination) is a good representation of the LVDS input termination. CLKoutX/CLKoutX* would be changed to CLKinX/CLKinX* and the LVDS reciever would be the LMK00308, but everything else would be the same for an LVDS input.

    For an AC-coupled LVDS input, a 100 ohm resistor must be placed across CLKinX and CLKinX* and a 0.1 uF capacitor must be placed before CLKinX and CLKinX* as shown in the image below.

    The data sheet you have is the correct data sheet. Since the terminations for an LVDS input and output are the same, we only have the LVDS output terminations shown in the data sheet.

    Regards,

    Kia Rahbar