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TCA4311A: Can I connect Backplane to SDAOUT / SCLOUT?

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Replies: 3

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Part Number: TCA4311A


My customer has a question about TCA4311A.


My customer is trying to connect as follows:

- SDAOUT/SCLOUT: backplane

Because they use the card as a master for I2C communication, they think it is necessary to connect as such.
Is such a connection possible?

I think that the connection should be as described in D / S.
That's because that connection is necessary to support hot-swap.
And I think that the card side can be used as a master for I2C communication even if it is a D / S connection.
Is my understanding correct?

Best Regards,

Kaede Kudo

  • Hey Kaede-San,

    This device is meant to have SDA/SCL in connecting to the backplane from the card. If you flip this, the device will not properly support the hot swap function.

    Typically, the master would side on the backplane of the device. It is possible to have a master on the card of the device but I would still recommend you keep the SDA/SCL in side of the device to connect to the backplane if you want to use the hotswap feature.

  • In reply to TRX Bobby:

    Hello Bobby-san,

    Thank you for your answer.

    Does it mean that TCA4311A should be connected as follows?

    - Backplane: SCLIN/SDAIN
    - card: SCLOUT/SDAOUT

    Even if the master of I2C communication is either the card side or the Back plane side.

    Best Regards,

    Kaede Kudo

  • In reply to KAEDE KUDO:

    Hey Kaede-san,

    "Does it mean that TCA4311A should be connected as follows?"

    - Backplane: SCLIN/SDAIN
    - card: SCLOUT/SDAOUT

    Yes, this was how the device was designed. In section 8.4.1, the third paragraph discusses SDA/SCL IN being plugged into the backplane.

    The reason why I say SDA/SCL IN should plug into the back plane is because that side monitors for a stop condition/idle condition. SDA/SCL OUT does not.

    Typically we see SDA/SCL OUT feed into memory in server type applications. This ensures when the device is connected, the slave does not glitch upon insertion and communication on the I2C bus shouldn't be affected.

    "Even if the master of I2C communication is either the card side or the Back plane side."

    There isn't any issue if the master is on the SDA/SCL OUT side of the device. Once the device detects an idle/stop condition, the master should be able to communicate to the backplane from the SDA/SCL OUT side anyways.