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PCA9548- Can we pull up the upstream I2C to 3.3V and down stream to 2.5V

Prasad Ajay
Prodigy 40 points
Other Parts Discussed in Thread: PCA9548A

Hello ,

I am using PCA9548 as I2C mux in my design, to connect Upstream I2C from a 3.3V device to a 2.5V down stream device.

Is it possible to provide a pull up of 3.3V on upstream I2C ,and connect the down stream I2C to a 2.5V device with a pull up of 2.5V?

Need to make sure that the voltage level on the 2.5V device I2C depends just on the pull up provided in the downstream I2c signal and does not depend on the upstream pull up.

Will PCA9548 act as a voltage translator? so that the 3.3V pullup on Upstream I2C will not damage  the 2.5V device on the down stream.

Snapshot of connection is given below.

  • 0
    TI__Genius 16430 points

    Hello,

    Yes, you can translate voltages between the sides of the switches. If you look at the PCA9548A datasheet at the Typical Application section on page 17. You'll see a graphic highlighting exactly this functionality.

    As a note, you should tie your device VCC to your LOWEST voltage pull up (IE, tie VCC to 2.5V for the device, and you can pull up the SDA line on the upside part to 3.3V and it should work)

  • 0
    TI__Genius 16430 points

    Whoops. I read your graphic and for some reason saw 2.7V instead of 2.5V. While the graphic I attached shows 2.7V, we are capable of down to 1.8V translation.

    See below snippet from datasheet.