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TCA9535 communications with I2C master device

Philip
Expert 1510 points

Other Parts Discussed in Thread: TCA9535, TXS0102, PCA9306, TCA6416A

Hi there,

If I want to use TCA9535 in a 5V supply voltage (Vcc) environment, and have it communicating with a 3.3V I2C master device (MCU), do I need voltage level translators

or level shifters for the I2C signals to allow proper communication?

If yes, do you have any application notes for this?

Please kindly advise, thanks.

 

  • 0
    TI__Genius 9085 points

    If your MCU can handle 5V signals, you could use 5V pull-ups on the SDA/SCL lines.

    However, you cannot use 3.3V signals to communicate with the TCA9535, since the VIH for the TCA is 3.7V [Vcc*0.7] for a 5V VCC.

    If you MCU IOs are not 5V tolerant, I would recommend using the TXS0102 or the PCA9306 for voltage translation.

     

    I do not know of any application notes, but if there are further questions, please post them here!

  • 0 in reply to Hattie
    Expert 1510 points

    Hi Hattie.

    I understand this device TCA9535 has Vcc supply voltage of 1.65 to 5.5V.

    If MCU SDA/SCL line is at 3.3V, can I fix TCA9535 at 3.3V as well?

    In such case, I would not need an external voltage translator or TCA6416A already.

    Would fixing 3.3V for TCA9535 Vcc operation has any issue on the I/O ports and the SDA/SCL line?

    Please kindly advise.

  • 0 in reply to Philip
    TI__Genius 9085 points

    Yes, you can set the VCC of the TCA9535 to 3.3V so that it communicates at 3.3V levels on the SDA and SCL lines.

    The IO ports will have a VOH of around 3.3V (VCC). But they will also be 5V tolerant.

  • 0 in reply to Hattie
    Prodigy 10 points

    If I have Vref1 connected to 3.3V and Vref2 connected to 5V, can I connect EN to 3.3V? The datasheet only shows application circuits where 5V is connected to EN (via a 200k series resistor), but my MCU outputs 3.3V. Thanks.