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TCA9548A: TCA9548AMRGER Queries

Dilip Namdeo Mohol
Intellectual 1965 points
Part Number: TCA9548A

Tool/software:

Hi  Team,

One of my customer is using TCA9548A in their design  and have few  technical queries about its behavior in specific scenarios, as detailed below:

  1. Power Sequencing:
    • If the pull-up resistors on the output lines of the TCA9548A are tied to a 3.3VA supply, which powers on before the device's Vcc (3.3V), will this cause back-powering through the I²C lines into the TCA9548A?
    • Would this sequence lead to any undefined behavior or reliability issues for the multiplexer?
  2. Back-Powering Tolerance:
    • Does the TCA9548A have internal protection mechanisms to handle such cases? If so, are there specific guidelines or limitations we should follow to ensure safe operation?
  3. Pull-Up Voltage vs. Vcc:
    • Is it mandatory for the pull-up voltage on the I²C lines to match the Vcc of the TCA9548A, or can it differ (e.g., 3.3VA for pull-ups and 3.3V for Vcc)?
  4. Leakage Current:
    • If the pull-up resistors are active while the TCA9548A Vcc is off, what is the expected leakage current through the I²C lines?

We would appreciate it if you could provide clarification or relevant documentation addressing these points. Your guidance will help ensure that our implementation aligns with the device's specifications and operates reliably.

We have a few technical queries about its behavior in specific scenarios, as detailed below:

  1. Power Sequencing:
    • If the pull-up resistors on the output lines of the TCA9548A are tied to a 3.3VA supply, which powers on before the device's Vcc (3.3V), will this cause back-powering through the I²C lines into the TCA9548A?
    • Would this sequence lead to any undefined behavior or reliability issues for the multiplexer?
  2. Back-Powering Tolerance:
    • Does the TCA9548A have internal protection mechanisms to handle such cases? If so, are there specific guidelines or limitations we should follow to ensure safe operation?
  3. Pull-Up Voltage vs. Vcc:
    • Is it mandatory for the pull-up voltage on the I²C lines to match the Vcc of the TCA9548A, or can it differ (e.g., 3.3VA for pull-ups and 3.3V for Vcc)?
  4. Leakage Current:
    • If the pull-up resistors are active while the TCA9548A Vcc is off, what is the expected leakage current through the I²C lines ?

 Reagrds

DIlip

  • 0
    TI__Genius 17745 points

    Hello Dilip,

    1. This sequence is exceeding device operation and may cause undefined behavior and reliability issues. The TCA9548A doesn't have any protection when the device is off.

    2. There is no internal protection circuitry for this implementation. I suggest to follow the recommended operation conditions to avoid issues. 

    3. No, it is not mandatory, it can be lower. Vcc can be 3.3V and VDPUx = 1.8V.

    4. I cannot predict device behavior under conditions exceeding its recommended operation limits. Its behavior is unpredictable. 

    Thanks,

    Nir