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CDCLVP1102: LVPECL to LVDS

Vincent Chen64988
Expert 4480 points
Part Number: CDCLVP1102

Hi Team,

My customer would like to use CDCLVP1102 and the interface of receiver side is LVDS. we referred to app. note of SCAA059C for LVPECL to LVDS connection(Figure 5) and found two question. Please could team comment it.

http://www.ti.com/lit/an/scaa059c/scaa059c.pdf

1. Only negative pin of receiver has bias resistors, doesn't positive pin neet it?

2. LVDS common mode voltage is 1.2V, right? Why bias resistors shift it to 1.65V?

Thanks very much.

Vincent Chen

  • 0
    TI__Genius 16845 points

    Hi Vincent,

    A1. The inverting input pin does not require external bias. The 100-ohm termination resistor applies a DC bias to the inverting input as well.

    A2, Use bias resistors of Rtop = 8.7K and Rbottom = 5K to achieve 1.2V bias from a 3.3V rail. If you need to attenuate the swing from 600mV to ~350mV, you can add 70ohm series resistors at the LVPECL driver after the 150-ohm biasing resistor before the transmission line.

    Kind regards,
    Lane