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Is I2C bus on BQ76930 daisy-chainable ?

S O
Prodigy 20 points
Other Parts Discussed in Thread: BQ76930

Hi,

I'm currently trying to conceive a system of BMSs to monitor 6 cells on series, that forms a pack. And I want to parallelize this pack x times (at least 6 times). It means that I use 1 BMS by pack so globally the system includes a maximum of 6 BMS (BQ76930).

Then, all BMSs need to communicate their information to a single micro-controller to give data to the user and manage the BMSs (add some functionnalities for example) . The problem is that most of micro-controller can manage a maximum of 2 I2C buses. So I need a device that has all the I2C buses of BMS in input and one I2C on output that manages the communication inside.

This component is called daisy-chaining device, but apparently the bus need to be compliant with this device (or type of structure). So Is I2C bus on BQ76930 daisy-chainable ?

Thanks for your advice,

Sami.

  • 0
    TI__Guru 54715 points

    The bq76930 devices do not chain one to the next. You could get a bq7693002 and a bq7693006 for example and put them on the same bus since they have different addresses, but this is only 2 devices. If you are building identical modules, the devices would have the same address, so if you need to talk to more than one on the same bus, you will need a multiplexer or other switch.  If the parts are at a different reference potential (VSS at different voltages) you will need an isolator to reach the different voltage levels.

    Check the interface voltage levels on each side of the interface part and connect appropriately.

  • 0 in reply to WM5295
    Prodigy 20 points
    Thanks very much for your quick answer.

    If I understand correctly, it means that I need at least 2 different references of bq76930. Basically I need 4 BMSs that can communicate with the micro-controller (in write and read). So I need 4 devices with different references that can be put on the same bus. Is it possible to do that ?

    Thanks by advance.

    Sami
  • 0 in reply to S O
    TI__Guru 54715 points

    There are only 2 addresses available, see the table in the datasheet.  For more devices on the same bus I expect you will need an I2C bus multiplexer or other switch.  If the VSS pins of the bq76930 are at different voltages, you will likely need isolators or level shifters.

  • 0
    TI__Expert 6085 points

    Ideal I2C full compliant devices, can drive the SCL bus low, when SLAVE configured device ready to talk to the host. Thus making it desirable to be implemented  in  daisy-chain  configurations.  the bq769xx devices do not have driver to pull the SCL low. if there is communication interface that can act between the slave and the host SCL bus, may be there is solution. but its unproven and sorry cannot share a working design.