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TCA4307: I2C Remote sensor stuck bus protection

Phillip Karls
Prodigy 50 points
Part Number: TCA4307

Tool/software:

Are there any concerns when using the the TCA4307 in the following fashion:

Basically I have an I2C bus controlled by some controller, with some local I2C devices, and some remote I2C sensors. I need to make sure the remote sensors cannot cause the I2C bus to get stuck. 

Section 8.2.4 suggests that this should be fine, but Section 8.2.1.2 has me concerned.

The remote sensors are hardwired, so I don't care about hot swap protection.  

  • 0
    Guru 317060 points

    The TCA4307 uses a dynamic voltage offset, i.e., for low-level signals, the output voltage is always higher than the input voltage. So with two TCA4307 in series, you get the sum of two offsets.

    Your 10 kΩ pull-ups are relatively weak, so I'd estimate that your VOL does not become dangerously high. (And two sensors do not actually need to see each other.)

  • 0
    TI__Mastermind 47888 points

    Hi Phillip,

    The parallel design looks to be fine. I believe it should work. 

    Vos = 60mV (typ). This means if the controller pulls LOW with a VOL = 0V, the VOL seen at any of the remote sensors will be 60mV. This estimate does not include the pull-up resistor current however, so I expect VOL to be slightly higher but not by too much since 10k pull-up are in use. 

    Regards,

    Tyler