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ISOW7842: How to use the isow7842 for isolating the USB and SWD?

joongwan kim
Prodigy 20 points
Part Number: ISOW7842

Hello, TI

I am Korean, so My English may be hard for you to understand.

I try to use the ISOW 7842 for isolating PC and MY Hardware(PCB)

so, I have a question

I have known the usb and swd are two-way communication.
if i use the isow7842 for isolating, Do i have to short the IN A and OUT B, IN B and OUT A in ISOW7842 for connecting DM and DP in USB?
and the same way, do i use ISOW7842 for connecting SWDIO and SWCLK ?
and if I use two ISOW7842, can I short each VISO?
please explain it as the figure if you can.
  • 0
    TI__Guru 55815 points

    Hi Kim,

    Welcome to TI E2E Forum!

    Like you have mentioned earlier, USB is a bidirectional interface while ISOW7842 supports only unidirectional channels. When you connect two opposite direction channels back-to-back, the device gets locked when one of the output goes to LOW.

    For example, let's assume you are connecting CHB and CHC back-to-back. When OUTB is LOW, it will hold INC also LOW. Since INC is LOW, OUTC will also be LOW. Now these two channels will hold each other permanently at LOW irrespective of the external input. Hence, you cannot achieve bidirectional channels by directly connecting two unidirectional channels.

    Sorry, I am not familiar with SWD interface. If this is a bidirectional interface then ISOW7842 cannot be used.

    No, you cannot connect VISO of two ISOW7842 devices together. This is not supported.

    Let me know if you have any other questions, thank you.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 20 points

    So, can you recomand the other ic for bidrectional?

  • 0 in reply to joongwan kim
    TI__Guru 55815 points

    Hi Joongwan,

    Sorry, we currently do not have an isolator that can be used for USB isolation. If there was a device then I would have definitely suggested you the part. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Guru 55815 points

    Hi Joongwan,

    I will go ahead and mark this post closed, if you have any further questions please respond this post anytime. Thanks.

    Regards,
    Koteshwar Rao