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BQ51050B: QI charging with BQ51050B: No end of charge detection

Benjamin Eymard
Prodigy 30 points
Part Number: BQ51050B
Other Parts Discussed in Thread: BQ51052B

Hello,

I'm currently using BQ51050B to charge the battery of a device.
The charge seems effective, unfortunately, the end of charge is never reach, even with charging current way lower than the end of charge current.

Ibulk is set to 360 mA and I tried various values for Rterm, from 2400 Ω (10% of Ibulk so Ieoc = 36 mA) to 5 kΩ (20.8% of Ibulk so Ieoc = 75 mA) but the BQ never released the CHG pin even with charging current as low as 25mA (measured between the charger and the battery).

I read here that it might be because this BQ is designed for higher currents. Do you know what is the minimal current detectable by this part ?

Also, wanting to charge the battery at 4.4 V, I was considering changing the regulator for the bq51052B, should I expect the same behaviour with the reference ?

Thank you,
Best regards

  • +1
    TI__Guru 72441 points

    Hello

    The termination will trigger when voltage at ILIM pin is lower than voltage at TERM pin.  The current at ILIM a sample of output current.  The current at TERM pin is a fixed current source.  

    Check voltage between the two pins to determine if they are working as expected.

    Also the Termination will have a Deglitch time of about 25mS, the IILIM voltage will need to be below TERM to set charge complete.  If the system is pulling current it may keep the unit from terminating.

  • 0 in reply to Bill Johns
    Prodigy 30 points

    Hello,
    Thank you for your answer. Strangely, as I tried to perform the measurements, the end-of-charge was triggered around a charging current of 60 mA. I'm guessing that changing Rterm value I might have failed my soldering and maybe the pin was floating.

    Nevertheless, I'm still a bit surprised by the current triggering the EOC, I've set Rterm to 5 kΩ, Rilim to 665Ω and Rfod to 200Ω (all resistors are 1%), I was expecting a final current around 75 mA but I guess it has to do with the precision Kilim and Kterm.

    I'll try to get a lower final current by empirical testing.

    Thank you,
    Best regards