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Original question:

ISO1540: about hot swap of ISO1540

ISO1540: How many ISO1540 could be connect in a I2C bus?

Will Wang47
Expert 6190 points
Part Number: ISO1540
Other Parts Discussed in Thread: ISO1541, SN6501

Hi team,

Customer wants to use ISO1540 in their project. And they need to parallel several ISO1540 in the I2C bus, so they need to know how many parts could be connected in the bus?

Could you give some comments to this question?

Thanks and Best Regards,

Will

  • 0
    TI__Intellectual 1210 points

    Hello Will,

    Thanks for reaching out to us.

    The iso1540 supports a bus capacity of 400pF on the secondary side.

    In general multiple isolated devices can be used on a bus. Could you maybe share some more system details? What mode is used? Is it a single master system? How many nodes are we talking about?

    Thank you for using the E2E forum.

    Best Regards,

    Matthias

  • 0 in reply to Mat1980
    TI__Expert 6190 points
    Hi Matthias,

    Thanks for you quick response.

    I think they are using multi-master system, and for now they want to achieve 3 devices in parallel.

    Should we let the connect the bus to the secondary side and connect the primary side to MCU? For I see the primary side has 40pF capacity, the secondary side has 400pF capacity.

    Hope you could give some comments to this.

    Thanks and Best Regards,
    Will
  • 0 in reply to Will Wang47
    TI__Intellectual 1210 points
    Hello Will,

    thanks for providing more details!

    Yes, the MCU is supposed to connect to the side 1 and the bus is supposed to connect to side 2.

    By 3 devices in parallel you mean to connect 3 devices on the bus side 2?

    Thanks and Best Regards,
    Matthias
  • 0 in reply to Mat1980
    TI__Intellectual 1210 points
    Sorry Will,

    please continue this conversation. I accidentially hit "TI thinks resolved"..

    Best Regards,
    Matthias
  • 0 in reply to Mat1980
    TI__Expert 6190 points

    Hi Matthias,

    Thanks for your feedback.

    I draw a pic of what I think customer want to do. For, side 2 has larger cap drive ability, so connect the bus on the second side. Could you give some comments to this?

    Let me know if there is anything unclear.

    Thanks,

    Will

  • 0 in reply to Will Wang47
    TI__Intellectual 1210 points
    Hello Will,

    thank you for providing the picture!

    We discussed this internally and this configuration works. I just noticed that you added the ISO1541, is that the device that you are acutal planning to use?
    Please make sure the connection is as in the scetch, so just having a single device connected on side 1 and the bus on side 2.

    Please let me know if you have any additional questions or system care abouts you want to discuss?

    A good way to add the power to this solution would be the SN6501 or SN6505. This app note discusses this briefly:

    www.ti.com/.../slla417.pdf

    Best Regards,
    Matthias
  • 0 in reply to Mat1980
    TI__Expert 6190 points
    Thanks, Matthias. Appreciate your help.

    Best Regards,
    Will