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LMK04832: IBIS AC Coupling using LVPECL

Cody Myers
Prodigy 60 points
Part Number: LMK04832
Other Parts Discussed in Thread: LMX1204,

When I add ac coupling capacitors for lvpecl driver to schematic I don't get any signal swing. What biasing is needed at receiver end? Trying to interface between the LMK04832 CLKOUT and LMX1204 CLKIN. 

  • 0
    TI__Mastermind 18950 points

    Hi Cody,

    Normally, AC-coupled LVPECL requires receiver end termination to an AC reference. Some of our products have an onboard AC reference pin that can be easily used, but the LMX1204 CLKIN pins have internal 50 Ohm termination (to what is not specified). The LMX1204 is a RF product and it seems to expect an input from a RF source, so I'll page one of our experts for the LMX1204 to help determine how to interface the two products.

    Thanks,

    Evan Su

  • 0 in reply to Evan Su
    TI__Guru** 108480 points

    Hi Cody,

    Looks to me this is an IBIS model issue. I do not familiar with modeling stuffs, I compared LMX1204 IBIS model with other devices with differential input, I guess Vinl and Vinh below are not correct.

    I modified these parameters to 1.2 and 1.35, please try if this fix your problem.

    lmx1204-m.ibs