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Original question:

BQ21040: #CHG pin never goes inactive when charge current goes below termination current

BQ21040: #CHG pin never goes inactive

Shreenidhi Patil
Expert 3936 points
Part Number: BQ21040
Other Parts Discussed in Thread: BQ24072

Hello Team , in the IC bq21040 , if my system load connected draws more current than the termination current  ( more than 10% of my Iset) does this  mean that the charging LED will never turn off ?

In this case the battery will eventually start drawing very low series current as the Vout will be regulated to 4.2V max .However as the system is drawing more current that Iterm the BQ21040 IC will never see a less than Iterm current ?

Is our understanding correct ?

  • 0
    TI__Guru* 75656 points
    Hello
    Yes - If they system load is greater than termination current the battery charge will not terminate. This could trip the 10 hour safety timer for charge time. If this trip power would need to turned off to reset.

    The timer can be turned off by floating or pulling TS pin high, see data sheet TTDM mode. But this will disable the battery temp monitor function. Unit will go thru battery charge but not turn off 4.2V. Would need to verify the battery can operate in this mode.

    The termination current is fixed on this unit, do not have the option to increase it. Another device to look at is the power path devices such as BQ24072 and other in the family. Battery charge and system load have separate paths.