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BQ78350: comunication issue with bq76940

Part Number: BQ78350
Other Parts Discussed in Thread: BQ76940,

Hello,

  I have a question about this error that I’m seeing…Seems like the i2c comms between the bq78350 and the bq76940 isn’t happening.

I’m not sure what’s causing this. Any idea what’s happening? I’ve tried reflashing fw and it’s not helping. 

It’s like the 78350 is sending and data to the correct address but it’s just sending empty data?

Any ideas?

Thanks,

Adam

  • Hi Adam,

    What hardware are you using? Is it an EVM or a different board? What specific part number are you using for the BQ76940? (there are different versions of the device and not all are compatible with the BQ78350). 

    Regards,

    Matt

  • Hi Matt,

    This is on our own design which has been working. This is a new issue that I just observed.
    We’re using BQ78350DBT-R1 (installing R2 fw) and BQ7694000DBT

  • Hi Adam,

    This is strange. Is the I2C bus capture behaving like this right from the beginning (right after boot)? If the BQ78350 is reading low cell voltages, it will initiate a voltage based Shutdown. This involves sending the command to the AFE to go into SHIP mode, but if it is not able to communicate with the BQ76940, I'm not sure what will happen. Are all of the voltages on the BQ76940 pins looking normal?

    Matt

  • Hi Matt,

    Actually, I was able to verify that the AFE was likely damaged due to TS2 and TS3 pins were shorted together causing a ~20kOhm path between VC5X and VC10X.

    Thank you for the support