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BQ21040: slow charging application - alternative device without safety timer?

Bart
Expert 6360 points
Part Number: BQ21040
Other Parts Discussed in Thread: BQ24041, BQ24086

Team,

we would need a standalone charger like BQ21040, but without the safety timer - we have a limited power source and need to limit charging current down to 20-30mA, so it will take more than a day to recharge battery (while the safety timer is fixed for 10h).

Also, we checked BQ24041 (no timer), but it has an Enable pin instead of TS pin, while we need to have both of these pins (just without safety timer). 

What can you propose?

Thank you.

  • 0
    TI__Guru 69116 points

    Hello

    Do you require TS function also, battery temp safety feature?

    The BQ21040 has the option to disable timer function also but the TS pin needs to be pulled high (TTDM).  The battery temp safety feature is disabled.

    The BQ24086 / 88 has both Timer Disable and TS.

  • 0 in reply to Bill Johns
    Prodigy 10 points

    But is there any option, that microcontroller could cancel or stop Charging cycle on BQ24086 / 88? 

    If we connect Rset to microcontroller pin, can we disable charging with that? If put to low, charging is set with Rset, if pin is set to high, charging is disabled? Would that work? 

  • 0 in reply to Simon Krulec
    TI__Guru 69116 points

    Hello

    I think the BQ21040 will reset 10 hour timer if the TS pin is pulled low then released.  If you have a microcontroller it could pull the TS pin low at some rate, every hour.  This would keep the safety timer from resetting.  The battery temp monitor function of TS could still be used.