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BQ24072: BQ24072 charging at much higher current.

Francesco Poderico
Prodigy 30 points
Part Number: BQ24072

Tool/software:

Hello there,

I'm using the BQ24072RGTT to charge a 3.7V Lipo battery.

The Iset is approximately 0.75A, and instead I am charging the battery at maximum current the input power supply can handle.

for example if I use a lab power supply and I set to 5V 2A, then the charging current is 2A.

The Gas gauge confirm that the current goes to the Battery, indicating me a -2000 mA ish.

I have then noticed that the charging LED is not ON unless I reduce the power supply current limit below 1.5A 

.For example if I set the lab power supply to 0.7A, then the charging LED is ON, instead when I set the lab power supply current limit to 2A, then the Charging LED is OFF.

Can you help me please?

  • 0
    TI__Expert 8275 points

    Hello Francesco,

    Thanks for reaching out.

    The BQ24072 has an absolute maximum input current rating of 1.6A. If the charger drew the full 2A from the power supply, that would exceed the spec and could have caused damage.

    It's possible the charger was damaged before the 2A test, but running 2A also could've contributed.

    Just to clarify, is the charger's input current always equal to the input power supply's current limit? For example, if the supply is set to 1A, does the charger draw 1A?

    Also, how many boards are showing this behavior? If there's another root cause here, I'd definitely like to figure it out. But with the absolute max rating exceeded, damage is a real possibility now.

    Best regards,

    Alec

  • +1 in reply to Alec Lehman
    Prodigy 30 points

    Hi Alec,

    I have tested so far 4 boards and all display the same issue.

    Starting from scratch with a new board, With the power supply setting of 5V, 1A (max), I see the power supply go to current limit and the voltage drops to 4.4V (because of the current limit).

    The charging LED is ON!

    if I further increase the charging current, let say to 1.6A or higher the charging LED goes OFF.

    Since the current limit is 750 mA, I think the charging is not working.

    I prefer not to increase the current limit to avoid damagin the chip as you said.

    The above behaviour is all across the 4 PCBA.

    The marking is CKP 338

    AKFP (I think)

    Is it possible the part fitted is incorrect?

    Thank you,

    Francesco