• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 2 answers
  • Subscribers 62 subscribers
  • Views 592 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.

BQ35100: bq35100: Different current values when in ACC and EOS mode

Hendrik van Essen
Prodigy 50 points
Part Number: BQ35100


Hello,

I'm failing to understand why I get different current values for different operating modes, while voltage and temperature are totally fine.

Please consider the following process:

0. Calibrate in ACC mode
1. Stay in ACC mode
2. Read current: -10 mA without load (correct)
3. Read current: -144 mA on load (correct)
4. Change mode to EOS
5. Read current: -1044 mA on load (incorrect)
6. Read current: -910 mA without load (incorrect)
7. Switch back to ACC
8. Current values are as in 2. and 3.

I couldn't find a reason for this behavior in the documents so far, but it's weird and I wanted to clearify this before we start our long term EOS draining test.

Best,
Hendrik

  • 0
    TI__Guru** 106050 points

    Hello Hendrik,

    If you send the GAUGE_START command in EOS is the current still wrong? In the different modes the ADC may not be operating until the gauge start command is sent.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Hello Wyatt,

    yes, I tried sending GAUGE_START before and after changing from ACC to EOS mode. Unfortunately, neither way changed the behavior I observed.
    When I compared the incorrect values in EOS mode with the correct values from ACC I noticed that the absolute difference between load and no load is exactly the same for both modes (134 mA), but in EOS there is an offset of exactly 900 mA for some reason?

    Best,
    Hendrik

  • 0 in reply to Hendrik van Essen
    TI__Guru** 106050 points

    Hello Hendrik,

    The GNDSEL may have some impact on the current accuracy, since it is related to the GND used for ADC conversion and right next the GMSEL bits. Generally the modes shouldn't be transitioned in the field, so the gauge would stay in one mode for the lifetime of the gauge, if you calibrate in EOS mode is the issue still present?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Hello Wyatt,

    the GNDSEL bit is not set. We transition from ACC to EOS, because the TRM states that "the bq35100 device must be [...] in ACC mode [...] AND the GAUGE_START() command should have been sent" before entering the calibration mode. So, is calibrating in EOS really an option here?

    Best
    Hendrik

  • 0 in reply to Hendrik van Essen
    TI__Guru** 106050 points

    Hello Hendrik,

    You are correct, I reviewed further and it seems the calibration in ACC should accommodate for all modes.

    Have you tested with other devices or tried to upload the SREC again? I have not seen this behavior before so it seems this might be device specific.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Hello Wyatt,

    I have tried it with our custom board and a devkit board before. I have now also tested it with the second devkit board as well, but it is the same on all of them. Perhaps it is worth noting that they are all based on the same SREC file which I created from one of the (supposedly unused) devkit boards.

    I will try to add the SREC file here, maybe there is something wrong with it? (If the file is not attached when posting my reply, may I send you the SREC file via email?)
    What I was already wondering is where I can download an "original" SREC file if I want to? I was looking a few minutes for one, but could not find one.

    Best,
    Hendrik

  • +1 in reply to Hendrik van Essen
    TI__Guru** 106050 points

    Hello Hendrik,

    The default SREC is on the product page in the software development section: https://www.ti.com/tool/download/SLUC623

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    Thank you very much Wyatt,

    with the help of the default SREC I was able to identify the issue. I don't know why or when this was set, but AD I Offset was a really big number (19456 instead of 76). After setting it back to the default value I now have the same current measurements in all modes.

    Best,
    Hendrik