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BQ27510-G3: How long does the Gas Gauge take to start?

Atlant Schmidt
Expert 1530 points
Part Number: BQ27510-G3

We're using a BQ27510-G3 Gas Gauge in our design.

We've noticed that when the gas gauge is first powered-on (i.e., when we insert a battery into our portable device or first apply Vcc to our test breadboards), it will take about 2300 ms before the Gas Gauge seems to really be going. For example, here's a typical trace with our startup code reading the "Voltage", "Flags", and "Nominal Available Capacity" values from the Gas Gauge:

Is this to be expected?

Is the startup time officially documented anywhere (such as the BQ27510-G3 Data Sheet or in some Application Note)?

Our Battery Engineer thought he remembered seeing this time mentioned in older documentation (such as the -G1 Data Sheet) but it wasn't obvious to me when I read that (although there are hints that several startup activities sum to just about our observed 2300 ms).

I ask because we'd like to set an upper bound on how long we should delay before commencing our battery monitoring activities and expecting accurate results. Right now, based on our experiments, we've set our real code to just blindly wait 3000 ms before commencing battery monitoring but a reference for that timing choice would be appreciated.

  • 0
    TI__Guru* 76230 points
    Hi Atlant,
    The gauge initializes upon start up. We typically inform our customers to wait 2.5s before any reasonable data can be accessed from the gauge. To avoid waiting a specific time, you can poll the initcomp (initialization complete) flag and after it sets you can then read meaningful data from the gauge.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Expert 1530 points
    Onyx:

    > The gauge initializes upon start up. We typically inform our customers to wait 2.5s before any reasonable data can be accessed from the gauge. To avoid waiting a specific time, you can poll the initcomp (initialization complete) flag and after it sets you can then read meaningful data from the gauge.

    Thanks! Is that 2.5 seconds documented anywhere (just so we can make a reference to it in our code comments)?
  • 0 in reply to Atlant Schmidt
    TI__Guru* 76230 points
    Hi Atlant,
    I haven't seen it anywhere either, this is just information gleaned from interaction with our firmware engineers from over the years. I agree we have to put it somewhere, but then again we do have the initcomp flag that addresses this.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Expert 1530 points

    Onyx:

    > I haven't seen it anywhere either, this is just information gleaned from interaction with our firmware engineers from over the years.

    Thanks. For now, we'll just put a URL in our code that leads to this discussion. ;-)

    > I agree we have to put it somewhere, but then again we do have the initcomp flag that addresses this.

    Anything you can do to improve the documentation is always a good thing and always appreciated out here in the field!

    Thanks again for your prompt help on both of my issues!