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BQ2416x - Charge LED lit without battery attached

Matthew Yenn
Prodigy 60 points
Other Parts Discussed in Thread: BQ24167

I have two designs that are using the BQ24167 device.   When I connect the DC source to the IN line the PG and CHG LEDs light up.  If there is a battery the CHG LED will go off some time later, presumably after a initial charge cycle has been completed.   But if there is no battery connected the CHG LED will stay lit.  If I connect and then disconnect the battery the CHG LED will possibly go out... but not always.   

Table 4 on page 24 of the datasheet states with 'No Battery Present' the CHG behavior should be High Impedence(OFF).


In all other modes e.g. USB input, battery only, supplement battery, charging etc. everything seems to be working.   

Is the CHG LED supposed to be on when there is no battery connected?  If not any suggestions on places to look?

Thanks

Matt

  • 0
    TI__Intellectual 1830 points

    Hi, Matt,

    For your question about BQ24167 : "Is the CHG LED supposed to be on when there is no battery connected?". The answer should be No.

    When there is no battery, the /CHG should be high impedance so the LED should be off, which is matched with the TABLE 4. But there will be exception when in the two below conditions:

    1. During the new first cycle, before the battery is fully charged, if TS fault happens, as the BQ24167 is stand alone charger, it doesn’t generate any interrupt pulse to the host, the /CHG will remain low. When the temperature decreases, it will charge again, with the LED lit, till it’s fully charged (without the 6 hour safety timer expires).
    2. If some load (any kind, power source, resistor, etc) is put to the BAT, it needs to check how many current it’s allowed to sink even with the power off. If it’s higher than about 50mA, even when the load is turned off, but with wire connecting, the /CHG will be low. The charger will take the sinking current as the Ibatshort current, and take the battery as deep discharged or short battery, and enters the first linear charge period. Figure 20.

    But I don’t quite understand some of your description ” If there is a battery the CHG LED will go off some time later, presumably after a initial charge cycle has been completed. ” Could you help to explain this? And what kind of battery do you use?

    Thanks. 

  • 0 in reply to Rocson He
    Prodigy 60 points

    Thanks for responding...

    The battery is a 3.7V, 7.8Ah battery with a 8.0A PCB and 10k thermistor. 

    When I have a battery connected to the bq24167, and then connect 9V the chg led lights up.  If the battery is already charged the led will turn off shortly after the 9v is applied.  If the battery is not charged then it will stay lit for awhile.   This is expected.   But if the battery is disconnected and I want to run from just the 9V the CHG led lights up when the 9V is applied and doesn't turn off.   That part doesn't make sense if the Bq24167 has a battery connected sense circuit.  

    The only thing connected to the battery pins 11,12 is a MOSFET that is driven from bgate.   On one design the MOSFET is populated and the other design it is not populated.  Since both designs behave the same i'm not convinced its associated with the FET.

    All testing has been done in the lab at ~20C.

    This is the battery:

    http://www.batteryspace.com/Customize-Li-ion-18650-Battery-3.7-V-7800mah-28.86wh-battery-module.aspx

    Thanks

    matt

  • 0 in reply to Matthew Yenn
    Prodigy 10 points

    i have the same behavior as matt mentioned in his first post.

    "When I connect the DC source to the IN line the PG and CHG LEDs light up"

    If a valid power supply is connected to DC input and there is no battery connected, both status indicators(CHG# and PG#) are LOW?!

    I found no indication for this behavior in the datasheet.

    any suggestions after all?

    thx in advance

    thomas