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TCA9543A: Working as two independant level shifters

Francisco Pastorini
Prodigy 100 points
Part Number: TCA9543A

Hello,

I am reaching out for guidance regarding the TCA9543A integrated circuit. I am currently facing a challenge with a microcontroller that operates at an I2C logic level of 1.8V, and I need to communicate with two different slaves. One of these slaves operates at 3.3V, and the other at 2.5V.

Upon reviewing the datasheet of the TCA9543A, I noticed that the minimum VIH is specified as 0.7*VCC. Consequently, it seems I should power the IC with no more than 2.5V. However, I am unclear about the relationship between the maximum output voltage of the switch and the supply voltage.

Is there any restriction in this context, or would it be sufficient to set the pull-up resistors to 3.3V for one channel and 2.5V for the other? Any insights or recommendations you could provide on this matter would be greatly appreciated.

Thank you for your time and assistance.

  • 0
    Guru 295500 points

    The switches are simple N-channel MOSFETs in common-gate configuration. When a signal line is pulled low, the switch is closed, and the signals on both sides are connected (i.e., the active I²C device sinks the current through all pull-up resistors). When the signal lines are high, the switch is open, and the voltages on both sides are determined by the respective pull-up resistors.

    Simply run the switch at the lowest signal voltage, 1.8 V. The pull-ups should use whatever voltage is appropriate for the devices on their bus segment. See the example in figure 16.

  • 0
    TI__Mastermind 18850 points

    Hello Francisco,

    I agree with Clemens on this.

    Here is the figure from the datasheet Clemens is referring to.

    Please let us know if you have any additional questions!

    Regards,

    Kameron