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PCA9543A: Same I2C slave address to the PCA9543ADR

Shibin Varghese
Intellectual 835 points
Part Number: PCA9543A

Hi Team,
I want to use two fuel gauges (BQ27411DRZT-G1A) in one of our products.
The two batteries are charged and discharged independently. 
Both the BQ27411DRZT-G1A are connected to the same I2C bus. 
The problem with BQ27411DRZT-G1A is that, it's no variant is available with a different I2C address. So we want to use a switch like PCA9543ADR.
Based on a brief reading of its datasheet of PCA9543ADR, I've some doubts regarding its design. Hope you can help me with
1). How is the PCA9543ADR distinguishes data between the salves (having the same I2C address) connected to its output ports?.
2). SInce BQ27411DRZT-G1A doesn't have an interrupt, I hope I can leave the ~INTx pin and `INT pin floating.
3). How can the master select slave1 and slave2?.
4). 

  • 0
    Guru 316690 points

    1. The PCA9543A uses simple electrical switches; all configued channels are connected together. When there are slaves with identical addresses on the downstream channels, then you must ensure that only one of them is enabled.

    2. See table 5-1; all /INT pins must have a pull-up resistor.

    3. Write a value of 1 or 2 to the control register; see section 8.6.2.

    See section 9.2 for an example.

  • 0 in reply to Clemens Ladisch
    Intellectual 835 points

    Hi Clemens,
    Thank you for your quick reply.
    I hope you are referring to this
    .

    and this 

    Since my slave devices don't have an interrupt pin,
    Providing a pull-up resistance to each ~INT pin is the maximum we can do.
    What is the significance of the ~INT pin?.
    Is that just for giving an interrupt to the host MCU?.

  • +1 in reply to Shibin Varghese
    Guru 316690 points

    Some I²C devices have interrupts. The PCA9543A allows to level shift these interrupt signals. You do not need them.