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ISO7742: Step in the middle of edge problem

Reagan Li
Prodigy 545 points
Part Number: ISO7742

Hi,

Please see the attached waveform of Isolator ISO7742.

In MCR it is used for isolation of 100Mbps RS422.

ISO_ESU is single-ended signal from transceiver to isolator measured on isolator input pin.

RXD_ESU is single-ended signal from isolator to Zynq measured on isolator output pin.

Now it is suspected the abnormal edge will lead to bit error.

Could you please give some suggestions on how to remove the step in the middle of edge?

Thanks!

  • 0
    TI__Genius 17100 points

    Hi Reagan,

    Thank you for posting, and welcome to E2E!

    Please confirm which ISO7742 output pin "RXD_ESU" is observed in. This abnormal edge is not expected from our digital isolator outputs and may be a result of extra loads connected to the pin or misconnections.

    Please confirm the data rate is ~50Mbps and please share a schematic of the transceiver, isolator, and Zynq showing signal connections and additional components. If this schematic is proprietary, you may send me a Personal Message.


    Thank you,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    TI__Genius 17100 points

    Hi Reagan, all,

    The test setup below, as shown in Figure 15 of the ISO7742 datasheet, was used to obtain the Eye Diagrams in the ISO7742 datasheet:



    Discussions regarding the customer schematic and additional questions are continuing via email. Please feel free to reply to this thread or use the red and yellow buttons in the upper right corner to continue the conversation.


    Thank you,
    Manuel Chavez