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BQ27426: I2C address conflict with bq27742

Kay Chen53
Expert 2225 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQ27743, TCA9543A, SN74AUP1G04, SN74AUP1G32, SN74LVC1G3157

Hi there:

I'd like to check those 2 gauge whether have the same I2C address:

BQ27426： 8.3.1.1 I2C interface address: 1010101 


BQ27742 : 7.6.2 I2C interface address: 1010101

If they did, whether could change that or MCU need to do other buffer to addressing those two?

Thanks again! 

  • 0
    TI__Mastermind 43031 points

      Yes, these 2 gauge parts have exact same I2C address. If your design has to use 2 gauge parts on the same I2C bus, then we have a new gauge part bq27743 for your design. Please let's know if you need datasheet and EVM for the new part. 

    Thanks!

    Phil

  • 0 in reply to Phil Yi40
    Expert 2225 points
    Hi Phil:

    OK~I'll suggest customer whether could change the design for bq27743.

    But if the design is fixed, is there any way to prevent the conflict issue for this same I2C address?
  • 0 in reply to Kay Chen53
    TI__Guru* 76230 points
    maybe you could try using an i2c multiplexer
  • 0 in reply to Phil Yi40
    Expert 2225 points

    Hi Phil:

    thanks! Could you provide me the datasheet for reference firstly? (since like this P/N isn't released yet)

  • 0 in reply to Onyx Ahiakwo
    Expert 2225 points
    Hi Onyx:

    Thanks, I just find even bq27520, bq27531, bq27426, bq27421 have the same I2C address;
    Does that mean we can't use 2 gauge solution in a same project?
  • 0 in reply to Kay Chen53
    TI__Guru* 76230 points
    Hi Kay,
    No you can't. you have to use an i2c multiplexer if you absolutely have to.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    TI__Genius 14985 points

    Here are a few options to get around the duplicate I2C device address issue:

    a)     If your processor has a second I2C interface, it can be used to control the second gauge on a separate bus.

     

    b)    If you don’t have an extra GPIO and only have one I2C interface, you could use one of our I2C port expanders.  The TCA9543A is a great two channel device for such a project.

    TCA9543A: 2-Channel I2C Bus Switch With Interrupt Logic and Reset

    Product Folder: http://www.ti.com/product/TCA9543A

    Datasheet (PDF): http://www.ti.com/litv/pdf/scps206a

     

    c)     You can use a GPIO to effectively route SCL to only one of the devices at a time. 

    One way to implement this is with an inverter for the control signal and a dual OR gate to route SCL. 

    1.     Connect SCL from your processor to one of the inputs of each OR gate, A pull up resistor must be located on this node (2kOhm is ok).

    2.     Connect the non-inverted control signal to the other input of the first OR gate. 

    3.     Connect the inverted control signal to the other input of the second OR gate. 

    4.     Connect the first OR gate's output to SCL on the first gauge(A) and the second OR gate's output to SCL on the second gauge(B).

    5.     When the GPIO is high, you will communicate with gauge(A) and when it is low, you will communicate with gauge(B).

     

    SN74AUP1G04: Low-Power Single Inverter Gate

    Product Folder: http://www.ti.com/product/SN74AUP1G04

    Datasheet (PDF): http://www.ti.com/litv/pdf/sces571k

     

    SN74AUP1G32: Low-Power Single 2-Input Positive-OR Gate

    Product Folder: http://www.ti.com/product/SN74AUP1G32

    Datasheet (PDF): http://www.ti.com/litv/pdf/sces580i

     

    d) You can also use an SPDT switch to route the SCL signal to each of the devices.  The LVC1G3157 is a great fit for this.

     

    SN74LVC1G3157: Single-Pole, Double-Throw Analog Switch

    Product Folder: http://www.ti.com/product/SN74LVC1G3157

    Datasheet (PDF): http://www.ti.com/lit/gpn/sn74lvc1g3157