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TCA9548A: How should I protect an IC? when I do not use the slave side including an IC?

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Replies: 10

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Part Number: TCA9548A

Hi all

I have some questions.
1, If I don't use many slave side.(maybe one or two ch or many TCA9548A)
no I2C pull up resistors and slave any divice.
If I may let an TCA9548A damage, how should I cope?
2, Whether when I decide the supply voltage on TCA9548A, I can be careful?
(e.g., you obey the minimum voltage of the slave side or I obey the master side?)
Thank you
  • Hello,

    Yes, you do need to be careful when selecting the VCC voltage if the device will be used to translate voltage levels among different slaves. You would need to check the Vpass voltage and make sure it is no larger than the lowest slave supply voltage. You may want to reference section 9.2.1 of the datasheet for further details on this.

    Regarding your first question, with what kind of damage are you concerned? I think maybe I'm not fully understanding your question. Damage should not occur as long as the device is operated within the specified absolute maximum conditions, though. If damage does occur, the exact failure mode can be difficult to predict. If the failure is isolated to one channel, though, you may be able to cope to some extent by resetting the device and then leaving that channel disabled (so that the other channels can still communicate).

    Regards,
    Max
  • In reply to Max Robertson:

    Hello,
    Thank you for a reply.

    As for the question, I attach some TCA9548A to a board.
    but what should the TCA9548A not to use do?

    And I want to ship it if possible without adding pulling up resistance to a slave bus of unused I2C. (I want to empty it to let a client choose the resistance)

    May I destroy an IC by this setting?

    Thank you.
  • In reply to user5914582:

    No, this will not damage the device. It is OK to not connect a pull-up resistor to one of the output ports if the port is not enabled. You should be careful not to enable that port until a pull-up resistance is present, though, or else it may interfere with the I2C communication on SDA/SCL and the other active channels.

    Regards,
    Max
  • In reply to Max Robertson:

    I understood slave ports of the I2C bus how to use.
    And I understood that you did not need to pull up resistor.
    Because I evade damage to IC, can I use RESET pin?
    Do I need to turn of power of IC?
    Thank you
  • In reply to user5914582:

    You do not need to cycle power in order to reset the device; asserting the /RESET line low will trigger a reset. It should not result in damage.

    Max
  • In reply to Max Robertson:

    I want to protect unused TCA9548A on the board, is it all right even if I joint electricity?

  • In reply to user5914582:

    Sorry, I'm not sure what you mean by "joint electricity." Could you please clarify on this or describe it in a different way?

    Max
  • In reply to Max Robertson:

    I think that the IC which a customer does not use does not supply a power supply.
    (e.g., all right even if I tie I2C bus of the master side though I do not tie a power supply to this IC?)
  • In reply to user5914582:

    Thanks, I understand your question now. When the device is unpowered, its SDA/SCL lines will be high impedance. So, it is OK for an unpowered device to be connected to an active I2C bus. It will not disturb the communication, and the device should not become damaged.

    Max
  • In reply to Max Robertson:

    I understood it.

    Thank you

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