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BQ78350-R1A: BQ78350 Software Development

Niklas Baumgartner
Prodigy 50 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ76920, BQ78350, EV2400

Tool/software:

Hello,

I am in the middle of a BMS Design using the BQ76920 AFE. Now I would like to test the option to add a Fuel Gauge IC. The BQ78350 looks like the best choice, since it is designed to be used with the BQ76920 directly.

I have a few questions, regarding the implementation of the BQ78350:

1) How can the Software Development be done for this IC? Cost related, I do not have an EVM module or the required EV2400 Interface adapter. It looks like some configuration can (or must?) be done using the bqStdio-Software? If I would bring both ICs onto my own PCB, would it be possible to setup the BQ78350 with bqStdio by just connecting the SMBus (I2C) to the Computer? Maybe you could elaborate more, on how the BQ78350 is intended to be used during a "normal" design procedure.

Also, I could not find any TI-archive or GitHub-page where someone presented some C-Code for the BQ78350, so I am not sure, how I could even write Code on my own. I did that for the BQ76920 and it worked perfectly, but the BQ78350 looks much more complex.

2) If I understood correctly, the BQ78350 is not solely a Fuel Gauge, it is at the same time a "System Controller", also for the BQ76920? I intend to use the BQ76920 and BQ78350 on one I2C-Bus and interface them with an MCU (where I plan to write my own C-Code for both ICs on).

I would like to control the Front-End-Features of the BQ76920 and more or less only use the Fuel-Gauge-Feature of the BQ78350.

So, is it possible to control both ICs separately? Because in the datasheet schematics, the BQ76920-I2C-Bus is directly tied to the BQ78350-Bus. Or can I only write Code for the BQ78350, that then automatically controls all the BQ76920 features, like Balancing, Voltage Measurements, etc.?

Thanks a lot!

  • 0
    TI__Mastermind 37981 points

    Hey Niklas,

    1. Ideally it will be best to buy an EVM or design a custom board and use the EV2400 to complete the learning cycle and make all necessary data memory changes for your application. Then you can export the golden image file and use this for production. 

    2. You should be able to communicate to the BQ76920 independently of the BQ78350

    Regards,

    Nick Richards

  • 0
    Prodigy 50 points

    Thanks a lot for the quick answer!

    Ok,

    I have an I2C Setup where we communicate with an MCU but are separated galvanically through a Digital Isolator. So, I would connect the BQ78350s SMBus-Lines to this connection. As in the Dat.sheet, the BQs are connected via their respective I2C-Lines. If I now want to also control the BQ76920 separately, how can I wire this?

    Can I connect SMBus, and both I2C lines (BQ76920+BQ78350) all to the same I2C-Bus that is galvanically isolated from the MCU?

  • 0 in reply to Niklas Baumgartner
    TI__Mastermind 37981 points

    Hello Niklas,

    Yes, as long as the address for the BQ78350 and BQ76920 are different, you can connect both to the same lines.

    Regards,

    Nick Richards

  • 0 in reply to Adrian
    Prodigy 50 points

    Ok, thank you!

    Does not this not create a problem that the BQ78350 thereby sends "itself" a command, if it wants to address the BQ76920, since they are all on one bus together?

    I only have a few questions for the schematics of the BQ78350: (coming from the Dat.sheet)

    1) the resistor R57 at !DISP-Pin has somewhat of a strange value and what is its purpose? Also in the pin description it was stated it should be tied to VSS if the LEDs were not used?

    2) Is there a certain reason you use the CSD17381F4T Power Mosfet for this low expected drain current? I plan on using a BSS816NW here instead.

    3) Last but not least, what is the purpose of C23 exactly and does its value matter?

    Thank you again for your help!

  • 0 in reply to Niklas Baumgartner
    TI__Mastermind 37981 points

    Hello Niklas,

    Niklas Baumgartner said:
    Does not this not create a problem that the BQ78350 thereby sends "itself" a command, if it wants to address the BQ76920, since they are all on one bus together?

    No it would not, since the addresses is different it would not send the communication to itself.

    For the rest of your questions, I will need to talk with my design team and get back to you on that.

    Regards,

    Nick Richards