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BQ78350 manual and automatic control of FETs

Michal Solecki
Intellectual 295 points
Other Parts Discussed in Thread: BQ76940, BQ78350

Hi,

We are currently trying to test the protections on the BQ78350 used with BQ76940.

We are trying to enable and disable the CHG and DSG FETs but we can’t get them to open or close.

We are using our own board, but we previously tested and developed our interface with the BQ76940 EVM board.

We wanted to test the protections prior to installing the batteries, therefore we have an external power supply plugged on the PACK terminals to provide the power necessary for the board.

We have provided screenshots of the registers using BQ studio.

We have even tried to use the FET override mode (FET_EN = 0), to override control of the FETs. When we write to manufacturer address 0x001F or 0X0020, we see CHG_TEST and DSG_TEST bits set in ManufacturingStatus(), however, CHG and DSG bits are never set in OperationStatus().

The only odd thing that we see is that the INIT bit is set in BatteryStatus()  and it never changes state. The BQ78350 TRM never mentions what conditions must occur to leave the INIT state.

Please advise.

Thank you

  • 0
    TI__Mastermind 23156 points

    Can you send me your gg files?  I would like to look at a log file as you are trying to do this.  Do you have any PF flags?  Check your PF status bits, further down in your screen.  Let me know.

    -Francis Houde

  • 0 in reply to fhoude
    Intellectual 295 points

    There are no PF flags set either. I couldn't fit them in the screenshot, but I did check the PF status to make sure.

    Attached is the gg file that you requested

    5556.BQ78350.gg.zip

    Thank you

  • 0 in reply to Michal Solecki
    TI__Mastermind 23156 points
    I am not able to download the file. Can you retry?
  • 0 in reply to fhoude
    Intellectual 295 points
    I can't upload files since the forum changed to the new appearance.
    I have sent the .zip file by email.
    Thank you
  • 0 in reply to Michal Solecki
    TI__Guru 54715 points

     Hi Michal,

    I see above you are working with Francis on your issue.

    I was able to load your gg file to an EVM and the FETs work OK.  The KEY polarity is apparently different from the EVM default as I must remove the shunt to enable DSG.  The manufacturing test commands for the FETs (MAC 0x001F and 0x0020) only work  when FET_EN is 0 in the ManufacturingStatus register as you likely noticed.  Sending FET_EN with the test active will clear the tests.

    INIT is an indication that initialization is complete and the data should be good to use, the bit should normally be set.

    Since you have had experience with the EVM, you might do a comparison between the EVM setup and your new board to look for differences. Also I don't get the same SOC as your register view, so you must have updated the chemistry and possibly some made other adjustments. It may be useful to save a SREC and try this between boards, or set up again from a firmware installation.  The SREC will contain more data than the gg file and it could be helpful to send to Francis for anaysis if it is not resolved.

  • 0 in reply to WM5295
    Expert 2225 points

    We found that the pull-down was not properly size on the ALERT signal, preventing it from going down to 0.

    But it turns out that actual value needed is much lower than what is installed on the EVM.

    I am starting a new thread about this:

    http://e2e.ti.com/support/power_management/battery_management/f/180/t/389790

    Frédéric