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[FAQ] BQ24040 and BQ2404X family Charge Complete Pin Behavior, /CHG

Bill Johns
Guru* 79526 points

Other Parts Discussed in Thread: BQ24090, BQ25100, BQ21040, BQ24050, BQ24040

The BQ2404X family of charger has a charge complete pin, /CHG to indicate charge in progress or complete.  But under some conditions the battery charge has stopped (no current to battery) but /CHG indicates charge.  In other case the battery is charging (current to battery) but /CHG does not indicate charge in progress.

  • 0
    TI__Guru* 79526 points

    This also applies to BQ21040, BQ24050, BQ24090 and BQ25100 family of devices.

    The /CHRG pin in an open drain output used to indicate that a battery charge cycle is in progress. The pin will go low when the device detects a valid power supply and starts charging the battery. The pin will go high impedance when the device detects that the battery is fully charged (Change Complete/ Termination).

    In order to optimize end user experience the charger behavior under the particular cases below is as follows:

    1.)      If TS (NTC) pin indicates an over temp condition charge is suspended, but the /CHG pin will remain low since termination or charge complete has not been detected.  Charge will resume when temp is reduced and the /CHG pin will remain low.

    2.)     The BQ2404X will automatically restart charge if after termination/charge complete the battery voltage drops to Recharge (V-RCH). This is done to maintain the battery fully charged. In this case the /CHG pin will remain high-Z after termination even if the recharge has started.

    3.)     During OVP shutdown or Charge Timer Fault /CHG is high –Z

    Note on First Charge Cycle-- will start when power is applied, disable / enable using TS pin or detect battery insertion, /CHG is low. Start charge cycle but not First charge cycle exiting TTDM mode or battery voltage below V-RCH.

    Additional info see BQ24040 Data Sheet Charge Complete Data Sheet section 8.3.7 also see Table in section 8.4.1.

    Note -- Updated section 2 May 20, 2019 -- To remain high-Z