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BQ24070 charge time issue

Jamaal_Charles
Genius 3245 points
Other Parts Discussed in Thread: BQ24070

Hello,

I am using the TI BQ24070 charger in a product, and appear to be seeing the charge time out of spec. I have the charge timer set using a 100kohm 1% resistor, which when calculated with the minimum KTIMER spec, yields 99000*.313/3600 =  8.6hrs.  I am charging at 5C and see the charge stop at 8.1-8.2hours. Any idea why I am seeing this reduced time? I am not sure, as the data sheet calls out the indicated 8.6Hr value at 0C+.

Thanks,

JC

  • 0
    TI__Guru**** 166996 points

    Has the battery completed charging, i.e., VBAT = VBATREG and ICHRG<ITERM?

     

  • 0 in reply to Jeff F
    Genius 3245 points

    Hi Jeff,

    The charge has not completed. Charge state is indicated by STAT1,2 = off,off.  It does not appear to be temperature suspend related, nor sleep mode.

    Thanks

  • 0 in reply to Jamaal_Charles
    Genius 3245 points

    Hi,

    We have another question.  Anything I should be concerned about if I change the state of MODE (low to high) during charging, besides no longer limiting BQ current to 500mA?

    Thanks

  • 0 in reply to Jamaal_Charles
    Prodigy 5 points

    It would help to see the battery voltage and current with a scope.
    What tells you that charging has stopped, are you measuring current and see the current stop?
    What is the battery voltage when it stops charging?

    This part has DPPM dynamic power path management.
    If the system load is taking enough current it will subtract from the battery charge current.
    The TIMER is automatically adjusted when the battery current is reduced.

    See page 13 of the data sheet.
    Do you see V(TMR) being reduced, indicating its in DPPM mode?

    Changing the MODE pin while operating should not cause any problems.

  • 0 in reply to Ed Walker
    Genius 3245 points

    Hi Ed,

    I don’t have plots at the moment, but I do log event information in device EEPROM I can post now. I detect the various states of the STAT pins and battery voltage with HH:MM:SS.  Therefore I can tell battery charger state. The following is an excerpt of the timing, noting that RTMR=100kohm

    0000000012: 05:00:00 TS_BV              4.062V

    0000000013: 06:00:00 TS_BV              4.166V

    0000000014: 06:24:00 TS_BV              4.196V

    0000000016: 07:00:00 TS_BV              4.195V

    0000000017: 07:48:49 STATUS 040D2C01:

                                00040000:3  Charge Status – OFF    ….here STATS are both detected OFF

    0000000019: 08:00:00 TS_BV              4.157V

    0000000020: 08:30:00 STATUS 040C2801:

                                00010000:0  Battery charger disabled   ...I have a timer to at 8.5 hrs to cycle EN to reset charge and timer

    0000000021: 08:31:00 STATUS 040D2801:

                                00010000:1  Battery charger enabled

    0000000022: 08:31:01 STATUS 04092801:

                                00040000:2  Charge Status - Fast charging      ..detect charger FAST CHARGE mode via STATs

    0000000023: 09:00:00 TS_BV              4.195V

    0000000024: 09:07:00 TS_BV              4.195V

    0000000026: 09:07:01 STATUS 04052C01:

                                000C0000:1  Charge Status - Done charging         ..detect charge complete mode via STATs

     I thought DPPM only extends the charge timer?

    Thanks