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PCA9306: If I2C I/O pins are 5V tolerant, can I use a 5V I2C master at side 1 with Vref1 = Vref2 = 3.3V?

John Peck66
Prodigy 100 points
Part Number: PCA9306

I'm a bit confused about the datasheet's "5-V Tolerant I2C I/O Ports to Support Mixed-Mode Signal Operation" claim.  I have a board with the PCA9306 on it -- with Vref2 = 3.3V.  Vref1 will normally be 2.5V, but I need to bring this board up with an Arduino -- 5V I2C.  What if I connect Vrev1 = Vref2 = 3.3V and then drive side 1 with my 5V I2C?

  • 0
    TI__Mastermind 21005 points

    Hello John,

    Do you have a schematic or complete diagram?  We normally recommend the connecting Vref2 to EN and then attaching that to the Vdpu (IO voltage you are translating from)

    Vdpu can be 5.0V and Vref1 can be 2.5V.  Give me a diagram of what you want to  do and I can tell you the best way to accomplish it.  Do you need any buffering of the SDA/SCL bus capacitance. If so then you might want to look at buffers.  If the traces are small and you have a limited number of slaves on the bus then a simple translator like the PCA9306 is all you need.

    -Francis Houde