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BQ20Z95: IIC BUS data issue

Cherry Zhou
Mastermind 22235 points
Part Number: BQ20Z95
Other Parts Discussed in Thread: TCA9617A, BQSTUDIO

Hi team,

Here's an issue from the customer may need your help:

BQ20Z95 is used as battery gas gauge IC. IIC BUS as data interface.

Between MCU and battery, the customer use TAC9617A as IIC repeater.

They monitor the temperature data of battery by MCU with IIC bus, it's found there are some extremely low(-273.05, -272.55) and high(317, 5380.85, 5329.45) temperature data during monitor process, although the rate  less one in a thousand.

Whatever they change pullup resistor value, the extremely temperature always exist.

Could you help analyze why this issue happen and give a hardware solution? Thanks.

Best Regards,

Cherry

  • 0
    TI__Guru 57697 points

    Hello Cherry,

    I would recommend that customer check communication by removing the TCA9617A. This will allow customer to verify gauge operation. If they still see intermittent high/low temperature, then i would check the solder quality of the thermistors.

    I strongly recommend that customer refer to TCA9617A datasheet and follow all the design guidelines in it. Also make sure that the MCU communication code handles clock stretching and handles errors gracefully.

  • 0 in reply to Shirish
    TI__Mastermind 22235 points

    Hi,

    Thanks for your support.

    The customer jumped TCA9617 to connect MCU and battery, the issue still happened. so TCA9617 itself didn't lead to the issue.

    Changing the two other batteries, the issue still happened again. that mean battery solder may not the issue reason.

    It's found the issue temperature keep are -273.05 and -272.55, no other issue temperature after reduced the pullup resistor value.

    They suspect the issue may cause by battery itself or MCU IIC PEC (packet error checking) function. How to verify these two possibility?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru 57697 points

    Did customer check solder on thermistor leads?

    As you mentioned, it is most likely MCU code issue. The easy way to verify is to use bqStudio to log the data and see if the error can be reproduced. If it cannot be reproduced, then the MCU code will need to be checked.

  • 0 in reply to Shirish
    TI__Mastermind 22235 points

    Hi,

    How to use bqStudio to log the data? They have EV2300 to monitor the battery.

    But only found normal temperature as follow picture, no issue temperature record. is there others way to log temperature?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru 57697 points

    Hello Cherry,

    On the Registers tab, there is a "Start logging" button. Choose a file and let it run for a few hours. Then you can check the log file temperature column data.

  • 0 in reply to Shirish
    TI__Mastermind 22235 points

    Hello Shirish,

    They used EV2300 to monitor the battery discharging and record the log file. Here it's found follow issue in the log file:

    1) about he "Possible Error-See error log" information. where can be seen the detailed error information or error reason?

    2) you can see a time interval in the below picture, it's found several place data discontinuity in the log file. what's happen? is it a issue or normal situation?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru 57697 points

    Hello Cherry,

    bqStudio has a scan interval of 4 seconds for registers by default. Looks like this was changed.

    Hammering the gauge with communication can leave the gauge with not having enough time to perform simulations. We will need more data to know if the gauge entered an unresponsive state where there is discontinuity in the log. Can you provide more details on what bqStudio settings/selections were changed while taking the log?

    Infrequent communication errors are normal. These must be retried in the real system. You can get details of communication in another file that is in the same location as the log file. It should have "err" in the file name.