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TMUX136: used as I2C switch

Hailiang Zhang
Expert 6085 points
Part Number: TMUX136

Hi Team,

Could you pls check is TMUX136MRSER ok for I2C switch? Or pls recommend alternative for PCA9641PWJ?

Regards，
Hailiang

  • 0
    TI__Mastermind 26868 points

    Hey Hailiang,

    The TMUX136 is a passive device which will only pass a signal from input to output. The PCA9641 is a bus arbiter. It will redrive signals. So the TMUX136 wouldn't be the best part to replace the PCA9641.
    I'm going to forward this to our TRX team who would have a better solution. 

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    TI__Guru 56640 points

    Hi Hailiang,

    We don't have any devices from the TRX portfolio that can act as an I2C arbiter. 

    Are you able to email: Sanchez, Rosemary r-sanchez1@ti.com

    We would like to know the customer and opportunity size for this PCA9641 socket.

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 6085 points

    Hi Bobby,

    The real requirement is: two BMCs alternately access the fan board. Hence a 2ch switch is needed. A device in a small footprint package is required. Please help comment if TMUX136MRSER is an option?

    Thanks

    Regard
    Hailiang

  • 0 in reply to Hailiang Zhang
    Guru 271300 points

    The PCA9641 automatically detects which master is currently active.

    If you can change the board so that the switch is manually controlled with a GPIO signal, then you can use any general-purpose analog switch like the TMUX136. 6 GHz is overkill for I²C; this is a search for other 2-channel 2:1 switches in QFN/SON (I don't know what voltage you need): ti.com/switches-multiplexers/analog/products.html#480=2&1143=2:1 SPDT&2954=USON;VSON;WSON;UQFN;WQFN

  • 0 in reply to Hailiang Zhang
    TI__Guru 56640 points

    If the two BMC's both try to access the switch, then how does it know which one gets access or priority? What if there is active communication between a BMC and fan board while the other BMC takes control of the switch during that moment? The arbiter handles this situation through its hardware. Using a switch by itself means you need to create a system where this can be checked/monitored. Maybe using an open drain circuit on the select lines of a switch could work to avoid contention but then the BMC's need to monitor the activity on that select line at all times and it wouldn't be able to tell if there was a race condition where both BMCs try to control the switch at the same time by actively driving low. If you have a method to do this, then yes a 2 channel switch can work otherwise no you need an arbiter.