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BQ20Z95: IT gas gauge algorithm disabled in sleep mode ?

Antoine Gardiol
Prodigy 140 points

Part Number: BQ20Z95

Hi All,

We noticed that our gas gauge does not adapt the DOD vs bat voltage correctly when the chip is used with sleep mode enabled. Voltage and current are measured correctly but Remaining Capacity stay stable (it should not).

So can anyone confirm that the IT gg algorithm is disabled when the sleep mode is enabled ?

Thanks by advance.

Antoine

  • 0
    TI__Mastermind 27145 points

    Hi Antoine,

    Is the gauge entering sleep mode while the battery is being discharged? The device should only enter sleep mode when the measured current is less than the Sleep Current setting. If you have log files showing this issue, I can take a look.

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Prodigy 140 points

    Hi Ben,

    Thank you for your answer.

    I’ve made some measurements to show you what we observe.

    We’ve put our board in a very low power mode, where the bq20z95 SMB clock + data lines are down.

    The configuration bit [SLEEP] of Operation Cfg A (in flash) is set so that it enters sleep once we remove the cable to communicate with the chip.

    We suppose it enters the sleep mode correctly, because it does a CC Offset calibration (we can see that it’s the only flash parameter changing).

    As explained in the datasheet, CC Offset calibration is only done when entering sleep mode.

    We observe then the following :

    • The [R_DIS] bit of SBS.OperationStatus is set. It should not do that, unless it regularly goes out of relaxation mode, enters discharge mode and goes back to relaxation mode. [R_DIS] bit is normally set just after entering relaxation mode and cleared once DOD measurement could be done (after 30min). We have verified that the current never goes beyond the limit in that low-power mode (in our case, it is less than 0.2mA).
    • The Remaining Capacity is never updated. We normally observe an update every 5 hours when we are in that low-power mode and not doing sleep mode.

    You can see in attached fileBug_sleepmode.zip the printscreens and the GG config taken at various time. You can see the [R_DIS] bit is set in the second printscreen.

    Thank you for your help, and best regards.

    Antoine