• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 589 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ78350-R1A: BQ7694001 AFE and BQ78350-R1A no I2C Communication and no SMBus communication with STM32 MCU

rohsik_j
Prodigy 165 points
Part Number: BQ78350-R1A

I wanted to bring to your attention an issue we've encountered with the communication between the AFE, Companion, and the Microcontroller Unit (MCU) in our vehicle battery pack system.

Upon observation, we have identified an I2C communication failure between the AFE and Companion, as well as an SMBus communication failure between the Companion and MCU. The initial symptom was the absence of cell voltage information from the AFE. Despite conducting a Root Cause Analysis (RCA) for the board, no short or low-impedance at IC pins or REGOUT was observed at 2.5 volts. However, we did notice high temperatures at the IC, indicating a potential issue.

Further investigation revealed that there is no clock signal on the I2C clock line, and it is constantly pulled to REGOUT.

In light of this, we are actively troubleshooting the issue and exploring potential solutions to restore communication between the AFE, Companion, and MCU.

Our priority is to resolve this communication failure promptly to ensure the proper functioning of the vehicle battery pack system.

We observed this kind of failure in 3 boards out of 100 boards.

After replacing both the New AFE and companion then working and if with AFE old And new companion or Vice versa also not working.

We kindly request your expertise and support in identifying the root cause of this failure. If you have any insights or suggestions regarding this matter

  • 0
    TI__Guru 62326 points

    The concerning observation is the high temperature at the "IC" (which one?). Neither the gauge not the AFE will heat up noticeably unless something is very wrong.

    Do you have information what happened in your system that preceded this observation?

    From a debug perspective: Given the description of the problem (and that a fix requires replacing both AFE and gauge), your system should be analyzed if there's a chance that any of the abs.max. limits may get violated.

  • 0 in reply to Dominik Hartl11
    Prodigy 165 points

    Hi,

    please correct my statement about temperature,  Actually we did not notice high temperatures at both ICs,

    at what abs.max. limits may get violated, which can cause both AFEs I2C and Companion Smbus failure.

  • 0 in reply to Dominik Hartl11
    Prodigy 165 points

    "Do you have information what happened in your system that preceded this observation? "

    In BMS Architecture AFE(BQ7694001) then companion(BQ78350-R1A) and MCU(STM32L5) connecting, at pack level for outside world communication MCU CAN will be the one.

    So at the pack level we did not receive cell's voltage at CAN Message this is our first observation.

  • 0 in reply to Dominik Hartl11
    Prodigy 165 points

    thank you Dominik for your supportive reply

  • 0 in reply to rohsik_j
    TI__Guru 62326 points

    In general, violating any abs.max. can cause permanent damage. It's basically a specification that says that if you exceed it, there's nothing that TI can guarantee afterwards. It's not necessarily going to damage the part (it may, though) but it's outside the safe parameters for the process that was used to make the chip.

  • 0 in reply to rohsik_j
    TI__Guru 62326 points

    If the part constantly pulls SCL low, then there's a fundamental problem. It's not something that can be fixed with a configuration or anything that is within normal operating parameters. Something must have happened in your system that caused the part to fail (it doesn't just fail by itself - unless it had a borderline defect from TI, which is extremely unusual).

    * did this pack ever work or was is defective from the beginning?

    * if it worked before, what happened in the system for this to change?

  • 0 in reply to Dominik Hartl11
    Prodigy 165 points

    In our case, the SCL line consistently remains in a high state.

    * did this pack ever work or was is defective from the beginning?

    The BMS board underwent manufacturing and testing at the vendor's facility. Additionally, the BMS was subjected to testing at both the battery pack and vehicle levels, including an End-of-Line (EOL) test. All test results indicated that the BMS met the acceptance criteria and was functioning correctly.

    However, after some time, communication between the AFE, Companion, and MCU ceased.

    Further issues were observed with the Different BMS hardware, such as TS2 and TS3 experiencing shorts due to problems with the NTC mounting. This included instances of the NTC sensor's electrical insulation tearing out and making contact with one of the cell voltages, resulting in shorting TS2 pins. Additionally, a permanent AFE hardware malfunction led to incorrect temperature readings. Remarkably, despite these hardware issues, the AFE continued to communicate with the Companion. This we did RCA.

    What could be the cause of this communication failure between both ICs? If you've encountered similar scenarios before, please share the potential causes so that I can conduct a Root Cause Analysis in a timely and accurate manner.

  • 0 in reply to rohsik_j
    TI__Guru 62326 points

    We haven't seen a permanently stuck SCL = high between AFE and gauge. TI would have to do failure analysis on a customer returned part. I'll inform the FAE who works with your company for further instructions how to get this process started.