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BQ40Z50-R2: Exit shutdown goes in ROM Mode when temperature is 7-9°C

Emilien Chappatte
Intellectual 355 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50, BQSTUDIO

Hello,

I find a strange behavior during testing.

From BQ Studio, I send the command Shutdown. After some time, the device goes in shutdown and I have no comm.
If I put the charger voltage to wake up the BQ40Z50, it wakes up and I can resume communication with BQ Sutdio.

However, if I do the exact same thing, same device, but the temperature is in the range of 7 to 9° Celsius to BMON goes in ROM mode at wake-up !!
If i send command 0x08 (exit ROM mode), after all is working fine. Configuration is there and all is working as it should.

To be more precise, I use BQ40Z50R2, FW 2.11. I was able to have the issues with the only changes made to config :
1. 3 cells to 4 cells confg / 2. Rsense from 1mR to 3mR / 3. Charger present voltage from 3000mV to 12000mV
Except this, this is the stock/default config.

Can someone help me to understand what is going on ? Thanks !

Below some temperatures, commands (including to one that answer 9002 - ROM Mode) and the config

bq40z50_R2.11_4cells.gg.csv

  • 0
    Intellectual 845 points

     Hi Emilien!

    Could you show OpStatus flags from bqStudio registers window just after exit from Boot loader?

    Is it just single issue or you are observing the same on different bq40z50r2 gauges?

    Thanks

  • 0 in reply to Igor Elremont
    Intellectual 355 points

    Hi Igor,

    Thanks for your fast reply !

    No it's not a single board issue, we can reproduce this issue on any device. I already tested five, and other tests were done on more than 10 total.

    Yes here is the capture of the registers, a refresh just after exiting the ROM mode :

    What do you think ?

  • 0 in reply to Emilien Chappatte
    Intellectual 845 points

     Me have some assumptions but need more information to confirm them.

    If you change your gg-profile back to stock settings are you still observing the issue?

    Could you upload your full SREC to check some locations there. Hope it would not disclose anything private as it's almost stock image as you mentioned.

    Thanks

  • 0 in reply to Igor Elremont
    Intellectual 355 points

    Oki. I can try to change to a more stock profile, just setting the number of cells en FET enable should be the very minimum.

    Yes you can have the .srec files of course, as discussed this is not our production one and no disclosure issues with this one.

    Thanks for your quick support !

    (I add to append .txt to the srec to be able to post ? )

    bq40z50_R2.11_4cells.srec.txt

  • 0 in reply to Emilien Chappatte
    TI__Guru 52115 points

    Hi Emilien,

    I don't think I have seen this issue before.   Can you upgrade the bq40z50 firmware to the latest R3 firmware and see if the same issue occurs? Thanks.

    Andy

  • 0 in reply to Emilien Chappatte
    Intellectual 845 points

     SREC image and bqStudio OpStatus register have confirmed my assumptions, your particular device has never been sealed.

     Never-sealed device has some special undoc features in respect to BootROM entry methods so you probably observing the edge case of it.

     It's only my assumption, try to Seal device and check if issue still happens.

     Thanks.

  • 0 in reply to Igor Elremont
    Intellectual 355 points

    Hello Andy, I already tried but forget to mention, the R3 does exactly the same thing.
    I did another test, if I do a reset the problem is not present.


    Igor, for sure this device was never sealed, you should have ask  ;)

    But... what you say is perfectly working ! How this can have such a behavior ???
    I have no problem at all if the device is sealed !!

    Many thanks for your great help !!


    But this blows my mind... this is out of my understanding to have such behaviors. Can someone explain me a technical reason to this ? What I missed in the documentation ?

  • 0 in reply to Emilien Chappatte
    TI__Guru 52115 points

    Hi Emilien,

    I don't have an answer for now.  I would need to reproduce it in our lab so that we can take a close look at this issue.  Unfortunately,  we all work from home now due to the coronavirus.  I will check with our firmware team and see if they have any idea. Will share their feedback if they have some ideas. 

    Andy

  • 0 in reply to Emilien Chappatte
    Intellectual 845 points

     Hi Emilien,

     Good to know you have resolved the issue!

     Me think you did not miss anything in the documentation just because the feature which edge case you discovered is not documented in the TRM.

     You could wait untill TI experts will revert with their conclusion on the subject issue, but right now me have explanation (my version) of why so happens.

     For certain reasons the technical background of it could not be discussed on the public forum so if you still interested me could give you my interpretation of things over the private channel

    Thanks and regards