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dp83620 FX_SD connect

Jeff Wang100039
Intellectual 2810 points


Hi,

FX_SD is a I/O pin, form datasheet p34, this pin need provide offset 1.25V. customer fiber module output high form 2.2 to 2.6V, output low form 1.3 to 1.7V. how to do the connect?

  • 0
    TI__Mastermind 31600 points

    Jeff,

    The FX_SD pin is designed for LVPECL signal levels.  With the recommended termination, the DC level will be below the LVPECL threshold in the absence of any signaling and will therefore indicate that no signal has been detected. 

    In addition to reviewing the fiber module levels, we should also confirm the polarity.  Many fiber modules implement an LOS (Loss of Signal) output instead of an SD (Signal Detect) output.  What fiber module is the customer using?

    Patrick

  • 0 in reply to Patrick OFarrell
    TI__Intellectual 2810 points

    Hi Patrick,

    you are correct. customer fiber module use ATR-01103CT-ST,  output LOS,LVPECL level.  so FX_SD need inverse and level shift.  could you suggest a circuit for the connect?

    Thank you.

    Jeff

  • 0 in reply to Jeff Wang100039
    TI__Mastermind 31600 points

    Jeff,

    I just wanted to note the context of our communication via email.  When notified about the need to invert the LOS signal and provide an LVPECL compatible signal to the FX_SD input, the customer was able to resolve their issue. 

    Patrick