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CDCLVD1212: what will happen is no termination 100 ohm resistor on input of cdclvd1212

Jason Dai
Expert 3720 points
Part Number: CDCLVD1212

Dear E2E,

what will happen is no termination 100 ohm resistor on input of cdclvd1212?

BR,

Jason

  • 0
    TI__Genius 12705 points

    Hello Jason,

    Without the 100 ohm differential termination the swing at the input to the CDCLVD1212 will be higher than expected ~ 2x.

    There also may be some waveform distortion present from reflections due to mismatch

    Regards, 

  • 0 in reply to Liam Keese
    TI__Expert 3720 points

    Liam,

    thanks for your reply.

    May I learn why input swing will be higher than expected ~2x without 100 ohm termination resistor?

    BR,

    Jason

  • 0 in reply to Jason Dai
    TI__Genius 16845 points

    Hi Jason,

    Typical LVDS drivers switch a 3.5mA current source across the driver outputs. The standard LVDS termination is a 100-ohm differential LVDS load, which provides 350mV of swing.

    Assuming an LVDS receiver has an internal 100-ohm termination, placing an external 100-ohm will provide a double termination (only one 100 ohms is required / recommended). In this case, the parallel combination of both resistors will halve the swing.

    Kind regards,
    Lane