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Properly isolating I2C for powered off MCU

Discussion in 'Programming/Internet' started by kr4sh, Sep 16, 2020.

  1. kr4sh

    kr4sh Guest

    What is the proper way to isolate the I2C lines of two devices where one is powered on and the other can be powered down? I'm not 100% sure if isolation is even necessary, but I suspect it is.

    Here is a simplified explanation of what I am doing: I have a MCU and an RTC connected to each other via I2C. The MCU can be powered down while the RTC continues to be powered (the same 5v supply). The MCU and the RTC remain connected via I2C. Here is a rough diagram:


    The first thought that came to mind was that I could use a MOSFET on each I2C line so that when the power is cut to the MCU, it severs the connection on SCL/SDA. Then I googled a bit and discovered TCA4311 which looks like it is basically built for this purpose. TCA4311 looks pretty interesting. I think pulling the EN pin to ground on the TCA4311 is all that is needed to sever the I2C lines.

    I was hoping to get some feedback since I am a newbie. Does the TCA4311 sound like a good strategy? Or am I way off? Thanks in advance!

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