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TMUX1574: I2C Muxing between SoC and MCU

Saminah C
Genius 9132 points
Part Number: TMUX1574
Other Parts Discussed in Thread: TS5A21366

Hi,

I am looking for a solution for  I2C Muxing between SoC and MCU.

When the SoC is on, it is master to both MCU’s I2Cs. But when SoC is powered off, switch would flip and have the MCUs be able to communicate; like MCU1 becoming master to MCU2 - The SOC will likely pull the lines low when it’s off - See block diagram below:

  1. Can I  use the TMUX1574 since one of their main careabouts is size?
  2. Will the TMUX1574 work with open drain signals?
  3. Do you know how this could be implemented more robustly?

Thanks

  • 0
    Guru 268780 points

    This will work fine; analog switches work with any signals that are inside their valid voltage range.

    Is it necessary for the two slave MCUs to be on different I²C buses? If not, an SPST switch like the TS5A21366 would suffice to disconnect the SOC.

    What exactly do you mean with "more robust"? Do you anticipate any problem with this circuit?

  • 0 in reply to Clemens Ladisch
    TI__Expert 3910 points

    Hi Saminah,

    For your configuration the TMUX1574 is currently our smallest device. 
    The advantage of having only one I²C BUS would be reduced board space, as you'll need less passive components, less board traces and a smaller switch (2 mm² vs 5  mm²). 

    The advantages of having two different busses is to communicate with both MCUs at the same time with the full bandwidth.

    Let us know if you have more questions.

    Best regards,

    Ambroise