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SN65LV1023A: SN65LV1023A differential output levels issue

Clement Macquet
Prodigy 10 points

Part Number: SN65LV1023A
Other Parts Discussed in Thread: DS10BR150

Hello,

I met a problem on component SN65LV1023ARHBR what generates abnormal differential outputs levels.

There are too high regarding the datasheet: 1.5V instead of 800mV for a 100 ohms load.

My measurement setup : SDS3054X-HD + SAP5000D

I tried with another 1GHz scope/probe and another board: same result. 

I bring you serializer and transmitter stages, scope screenshots and Figure 2 of datasheet.

Thank you in advance for your help.

 

sch_serializer_stage.png

sch_deserializer_stage.png

VOD_vs_RL.png

 

tx1_diff_eye_diagram.png

tx1_diff_signal.png

 

  • 0
    TI__Genius 16346 points

    Hi Clement,

    Can you specify where in the schematic/board you are measuring this voltage? I see you have a buffer between the serializer and the deserializer. 

    Regards,

    Matt

  • 0 in reply to Matt Smith
    Prodigy 10 points

    I measured these signals before LVDS redriver (DS10BR150) : ME_RX1P/ME_TX1P

  • 0 in reply to Clement Macquet
    TI__Genius 16346 points

    Hi Clement,

    I don't see this 1.5V VOD in the o-scope shots you attached. I'm assuming the voltage being shown is the voltage between the positive and negative LVDS lines (ME_RX1P and ME_RX1N). As the typical curve suggests for a 100Ohm load, the VOD will swing between +/-800mV, which is what your o-scope shots are showing. You might be misinterpreting the VOD spec to be in terms of peak-to-peak voltage, which is not the case. VOD is usually spec'd in terms of absolute value (sometimes denoted as |VOD|). 

    Regards,

    Matt 

  • 0 in reply to Matt Smith
    Prodigy 10 points

    Hi Matt,

    Yes it's around 1.6V/1.7V instead of 1.5V, mistake of me.

    For VOD, I just apply the formula shows below :

    But if you say that it's |VOD|, I understand and that solve our questions.

    Thank you.