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BQ27520-G4: RM value could be calculated accurately in sleep mode?

user6229777
Intellectual 690 points
Part Number: BQ27520-G4

If several hundred μA of current consumption occurs during sleep mode, will the RM value be updated to reflect this effect?

I feel it would be difficult to do from the followings.

Could you tell me your thought?

 V_SR = -0.125 ~ 0.125 V

Resolution = 14 bits

R_SENSE = 10 mohm

Minimum detect current = 0.125 V * 10 mohm / (2^14 / 2) = 1.5 mA/ LSB

I have the issue that after being left for a long time in sleep mode, the battery voltage is low but the RM value is very high.

  • 0
    TI__Genius 12686 points

    Hello, 

    Could you provide me with the log file and gg file for this? Even though the gauge is in sleep mode, the RM should still be updated every 20s. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 690 points

    Thank you for your reply.

    I attached the log and gg file.BQ_No1_.logF5S-0002_bq27520G4.gg.csv

  • 0 in reply to user6229777
    TI__Genius 12686 points

    Hello, 

    After looking at your log file, it looks like the unfiltered remaining capacity is getting updated. Can you please set the RCJUMPOK bit in the OpConfigD register? This should allow remaining capacity to update while in relax. See the image below taken from the Technical Reference Manual. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 690 points

    Hello,

    Thank you for your reply.
    I would try that with the RCJUMPOK bit set. I'll get back to you once I've done.

    Could you tell me the difference between "RemCap", "UnfilteredRM" and "FilteredRM"?

  • 0 in reply to user6229777
    TI__Genius 12686 points

    Hello, 

    The RemCap or "RemainingCapacity()" just reports the UnfilteredRM or the FilteredRM depending on whether the OpConfig D [SMTHEN] bit is set or not. Please refer to the below images taken from the BQ27520-G4 TRM.  

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Intellectual 690 points

    Hello,


    Thank you for your reply.
    I could understand the rerationship between "RemainingCapacity" and "Unfiltered/ Filtered RM" though, I'd like to know the more detail about the difference between "UnfilteredRM" and "FilteredRM".
    I'm not sure which is better for us to use as "RemainingCapacity".


    And I've tried the test with Opconfig D 0xDE.
    The attached is that log.
    Then there looks be no change from the previous log.
    Could you give me any advice?

    Thanks
    Best Regards,BQ_No1_03.log

  • +1 in reply to user6229777
    TI__Genius 12686 points

    Hello, 

    In the gauges, the filtered values are typically used to help minimize jumps in SoC reported by the gauge. I recommend referring to this FAQ for more on the difference between filtered and unfiltered gauging parameters. 

    In regards to your second question, you have the OpConfig D [SMTHEN] bit set which will result in the gauge reporting the filteredRM for the RemainingCapacity(). You should have OpConfig D [SMTHEN] = 0 for the gauge to report the unfiltered value for RemainingCapacity(). If you have the SMTHEN bit = 0, then you should observe changes in the RemainingCapacity reported by the gauge. 

    Regards, 

    Jonny.