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ISOUSB211: ISOUSB211 can't pass Eye-Diagram Test

Jon WANG
Intellectual 620 points
Part Number: ISOUSB211

Tool/software:

Customer using ISOUSB211 as a USB isolator, it can't pass Eye-Diagram Test. It can pass the Eye Diagram  test without using ISOUSB211. Further testing revealed that there was a difference in the comparison between the end signal (EOP) and the Eye Diagram chart. How to solve this issue? Thanks.

  • 0
    TI__Guru 55815 points

    Hi Jon,

    Thank you for reaching out.
    Please allow me to review your post and come back to you with feedback by end of tomorrow. Thanks.


    Regards,
    Koteshwar Rao

  • 0
    TI__Guru 55815 points

    Hi Jon,

    Thank you for your patience.

    The line that is crossing the eye in eye-diagram is from EOP. This is part of the additional random bits that are introduced in EOP by ISOUSB211. Such random bits are allowed for a hub and ISOUSB211 is a hub with two ports, therefore it is to be considered with two-hub timing budget. Please see below screenshot from USB standard stating that additional random bits are allowed in EOP for a repeater.

    Therefore, the eye-diagram should be considered as a pass. I hope this answers your question, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Intellectual 620 points

    Koteshwar,

        Customer do the USB1.1 Eye-diagram, could you pls help suggest whether does this Eye-diagram pass? Thanks.

  • 0 in reply to Jon WANG
    TI__Guru 55815 points

    Hi Jon,

    For full-speed transmissions, the SE0 for EOP width from the transmitter must be between 160ns and 175ns and the waveform that you have shared seem to meet these requirements. Therefore, this eye-diagram is considered a pass for a repeater. Thanks.


    Regards,
    Koteshwar Rao