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How best to monitor output signal of LMH0307 Cable Driver using LMH0376 ReClocker.

Jay Hardesty
Prodigy 100 points
Other Parts Discussed in Thread: LMH0376, LMH0307

Hi, hopefully this is a simple and quick question.  I'm wanting to use the eye monitoring capabilities of the LMH0376 SDI ReClocker to monitor the eye waveform output of your LMH0307 Cable Driver.  If my understanding is correct, it seems reasonable that I could take the differential signal generated by the LMH0307 Cable Driver (post biasing network and Capacitive coupling) and feed this directly into the LMH0376 ReClocker.  Basically, keeping everything the same as it would be in a typical configuration (minus the equalizer), with the exception that the coax cable would be replaced by foil traces on a the PCB.  

This seems reasonable, though I'd prefer not to toast a batch of PCBs, or overpower a bunch of ReClockers, simply because I misunderstood something.

If this is a reasonable method - I was also considering placing a small resistor (20ohm) in series with each differential (+/-) input signal to the ReClocker, so as to minimize any ringing.     

Thank you for your time and insight.

  • 0
    TI__Expert 3175 points

    Hi Jay,

    The eye monitor of the LMH0376 will indicate the internal receive signal based on the signals applied to its differential input pins. Feeding an output signal from LMH0307 cable driver to LMH0376 is not the intended application, but if you want it as an experiement, I expect the LMH0376 internal eye monitor will report the signals it sees.

    Please note the the LMH0376 input termination is 100 ohm differential, while the LMH0307 as a cable driver, is 75-ohm single end termination, or 2x75 if you used both the P and N outputs. I expect you need to have a 75-ohm to 50-ohm adaptor from LMH0307 to LMH0376. A simple approach is to place a 25-ohm R in series on both the P and N. This R along with the input C of the LMH0376 will form a low pass RC filter, and could cause degradation in the signal quality.

    regards,

    TK Chin

     

  • 0 in reply to T.K. Chin
    Prodigy 100 points

    Hi TK Chin,

      Great!  Thank you for your insight and suggestions.  I fully realize this is not a traditional application, though it seems like my best option currently.  As for the 75 single ended outputs of the Cable Driver, I actually intend to adapt the biasing network components to generate a 100ohm differential signal so as to meet the input needs of the LMH0376 ReClocker. 

    Please advice if anything else comes to mind, and thank you again for the prompt reply!