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BQ27421 Resetting

Jake Wegman1
Prodigy 70 points
Other Parts Discussed in Thread: BQ24072

Hello,

I am using the BQ27421 on a product I'm working on.  When capacity hits '0%', the RAM seems to lose the values that I had configured, which is a pretty serious issue.  The design relies on the BATLOWEN function of the gauge to inform the system when not to attempt a startup, which is not the default value, so if that functionality is wiped away by the gauge losing its configuration values, I've got a problem.  The battery voltage is still quite a ways above the minimum stated by the data sheet required to keep the 1.8V LDO alive, which is what I thought was being used to keep those values valid.  Is there another mechanism on the IC that would cause the IC to reset once the capacity hits 0%?

Thanks,

Jake

  • 0
    TI__Mastermind 24870 points

    Hello Jake,

    What voltage is the battery at when the device hits 0% SOC?

    Could you post the schematic to the internal forums?

    Thanks,

    Kang Kang

  • 0 in reply to Kang Kang
    TI__Genius 14985 points

    Hi Jake,

    As Kang mentioned, schematics would be helpful, and also your configuration settings.

    Specifically, what is your Terminate Voltage set to?  Is it possible that the protector in the battery pack is tripping and briefly removing power from the gauge, causing it to lose the RAM values?

  • 0 in reply to dMax
    Prodigy 70 points

    Hello Kang and dMax,

    Thank you very much for your prompt replies.  I'm still looking at some things, but I will start by including the schematic for the fuel gauge here.  I obviously can't send the whole schematic (proprietary), but the output of the gauge interfaces with a BQ24072; BIN ties to the thermistor on the battery pack6406.20140502_BQ27421.tiff.  I found last night that I had overlooked adjusting the Energy Capacity and the Terminate Voltage, so I'm working on that.  I've thought about the battery's protection circuit possibly coming on, and I will be looking at that as well.

    dMax,

    Saw your other response (posting here for others):

    http://e2e.ti.com/support/power_management/battery_management/f/180/p/338294/1182826.aspx#1182826

    I will take a look at the driver and see what I can incorporate; I was already using an older version of that driver for my development, and I'm guessing your team's version is a bit more bulletproof :-)

    Thanks for the quick responses,

    Jake