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LMK00334-Q1: AC-coupled HCSL Input

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Replies: 3

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Part Number: LMK00334-Q1

Hi,

In  my design ,LMK00334-Q1 differential HCSL clock inputs are from one clock generator , I want to use AC-coupled between generator and LMK00034-Q1. In LMK00034-Q1 datasheet, I found that "The CLKin input has an internal bias voltage of about 1.4 V"(on Page16), but I didn't find that whether there was also internal bias volatage on CLKin * pin?

If CLKINX*pin(CLKIN0* and CLKIN1*) has no internal bias volatge, I think I need to use DC-coupled. In LMK00334-Q1 datasheet, VCMD(differential input common mode volatge) mimum value is 0.25V ,but the generator output common mode voltage minmum value is also 0.25V ,there is no margin, in this case, whether DC-coupled is OK?

Thank you.

Regards.

Gavin

  • Hi Gavin,

    Yes, DC-coupling is OK. I recommend to DC-couple the input.

    Kind regards,
    Lane

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  • In reply to Lane Boyd:

    Hi,Lane

    1. whether there are  internal bias volatage on both CLKIn pin and CLKin * pin?

    2.If the input pins:OSCIN,CLKin1,CLKin1* are not used, can these pins be left floating?

    Regards

    Thank you

    Gavin

  • In reply to user3746678:

    Hi Gavin,

    A1. I just measured it on LMK00338EVM. CLKinX bias = 1.08V, CLKinX* bias = 1.35V . For this measurement, there is no input/output using the default EVM assembly.

    A2. Yes, these unused pins can be left floating

    Kind regards,
    Lane

    ____________________________________________________________________________________

    To design your own Clock Tree solution, visit WEBENCH Clock Architect ​​​​

    More information Clock and Timing System products: http://www.ti.com/clock-and-timing/overview.html