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BQ24104 Stuck in Temp Fault Mode

Jason Struble
Prodigy 50 points
Other Parts Discussed in Thread: BQ24104, BQ2054, BQ2004, BQ2000

I currently have a design using the BQ24104 IC.

The problem is that if the battery back goes to an over temp during the charge (or pre-charge phase) it indicates by flashing the STAT1. But if the user removes the battery from the charger (as most would because it has faulted out), the charger continues to indicate the fault because the Vts is still outside of the temperature range (although now at the other extreme).

This fault is also identified in the flow chart in the datasheet with a continuous loop waiting for temp to fall back into range. Either the charger has to be reset or a new battery placed on the charge to clear the fault. Anyone have an easy fix for this or does TI plan on fixing this obvious and serious flaw?

Thanks,

Jason

  • 0
    Prodigy 130 points

    i'm interested too because i'm actually working on a multicharger system with this chip.

    perhaps a bias system to keep Vts in good range (when no pack is inserted or removed) can solve the problem?

  • 0 in reply to franck morisseau
    TI__Mastermind 36110 points

    Thank you for your interest in Texas Instruments battery chargers.  You are correct that if the bq24104 detects a temperature fault, the fault condition is continuously displayed until you cycle power, initiate a new charge cycle by pulling /CE high and then low, or insert a new battery.  Your idea to force the voltage on the TS pin to indicate a good temperature also works.  You can monitor the battery voltage and when it goes away, you can connect a resistor to the TS pin to replace the removed battery themistor.  This can be accomplished by using an open drain comparator to compare the battery voltage to a reference voltage created by the VTSB pin.  When battery is present, comparator output is high.  WHen battery is not present, comparator is low.  Then connect a 10k resistor in series with a diode between the comparator output and the TS pin.  When comparator output is high, diode is back biased and the 10k is basically open circuited.  WHen the comparator output goes low because the battery (and battery thermistor) is removed, the 10k resistor replaces the missing battery thermistor.  Be sure to account for the voltage drops across the diode and the comparator output.

  • 0 in reply to Matthew Day
    Prodigy 130 points

    thank's tfor this solution but perhaps that  can cause some problems due to the battery detection scheme.

    when the battery is removed the chip detect a new one by an alternate voltage at the output.

    in this case with your comparator system  toggle /CE each time the chip try to detect a cell at the output.  

     

     

  • 0 in reply to franck morisseau
    TI__Mastermind 36110 points

    You are correct that the battery detection scheme will pull the battery voltage high and basically disable the circuit I described above.  If you filter the battery voltage with a capacitor and a diode, you can ensure that the voltage to the input of the comparator drops imediately when the battery detection circuit circuit pulls low, but takes a long time to charge when the detection circuit goes high.  This keeps the comparator's non inverting input low when a battery is not present.

  • 0 in reply to Matthew Day
    Prodigy 50 points

    This seems like a lot of work around for something that should be intrinsic to the IC. I find it odd the legacy products from benchmarq (BQ2054, BQ2004, BQ2000) don't perform this way and clearly detect when a battery attached to the system at all times.

    Adding comparators and reference voltages seems like an additional cost for something that could have been solved very easily in the IC itself.

    Unfortunately I did not discover this issue until now and we have just been through EMC and other regulatory testing. A redesign will set us way back.

    Jason