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LMK04828B - Loss of signal indicator

Hiroshi Katsunaga
Mastermind 6480 points

Hello,

My customer has a question about LMK04828B.

[Q]

My customer want to use the indicator of loss of signal for CLKin0/CLKin1 by the CLKin_SEL0/1.

Please tell me the setting method about it.

I tried it, but the result was unexpected.

I summarized the details in an attached document.

Please refer to it.

5670.LMK04828B-LOS_Indicator.pdf

Best Regards,

Hiroshi Katsunaga

  • 0
    TI__Mastermind 28550 points

    Hello,

    I think I know your issue, let me know if this resolves the issue.


    Do you have CLKin1_TYPE = 1 (MOS mode)?  We do say that MOS mode is needed for valid LOS, that is because of the steady state differential voltage, see next image.

    Note the voltage offset for Bipolar is 0 mV, as such there can be noise which tricks the LOS in the bipolar mode.  Note, it would technically be possible to add some pull-up/pull-down resistor to add a bias in bipolar mode to allow LOS to work as in MOS mode.

    73,

    Timothy

  • 0 in reply to Timothy T
    Mastermind 6480 points

    Hi Timothy-san,

    Thank you for your fast response.

    I understood your comment.

    I tried it and I was able to obtain an expected result !

    Thank you for your help.

    I have an additional question.

    [Q]

    There are the following description in the datasheet.

    "Bipolar is recommended for differential inputs like LVDS or LVPECL." (datasheet P.70 CLKinX_TYPE)

    If they input the differential signals like LVDS or LVPECL into it, is there the problem with setting CLKinX_TYPE with MOS ?

    Best Regards,

    Hiroshi Katsunaga