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BQ25101: BQ25101 run with a lot of power in battery absent state!

Truong Giang
Prodigy 170 points
Part Number: BQ25101

Hello,

My name is Giang. I am working on battery charger project which is using BQ25101YFPR. It works very well.  But in battery absent sate it run with a lot of power (2mA), I think it is too much.

Datasheet shows that:

+ QUIESCENT CURRENT = 1mA in actice mode, =6uA in Iout(done). I try to pull up OUT pin to 4.2V via a resistor 10k to to make the IC go to full charge state when the battery absent but it does not work. How we can go to DONE mode or STDBY mode to save power in battery absent state?

+ BATTERY DETECT ROUTINE run with 2mA IBD-SINK. How we can disable that current in battery absent state?

In schematic, I pull  down TS pin to GND via resistor 10k, IN connect to 5V, VSS connect to GND, pull down ISET pin to GND via resistor 2.26k, CHG# pull up via resistor 10k., OUT connect to battery.

Thank you,

Giang

  • 0
    TI__Guru 65846 points
    Hello
    The battery detection routine cannot be turned off.
    If the NTC (10k resistor on TS) was removed at the same time as battery you may have some options. You could test with 237k ohm resistor in place of the NTC with battery removed. Verify that this gives you the performance you are looking for.
  • 0 in reply to Bill Johns
    Prodigy 170 points
    Dear Bill Jones,

    When I install 10k resistor between TS and GND, the OUT pin create square signal (Vmax=4.28, Vmin=3.6, Prd=54ms), the IC run with 2mA in battery absent state.
    When I install 237k as your recommendation, the OUT pin create constant 4.2V and the IC run with a small current in battery absent state.
    It works as I want but I have one questions: If I install 237k (fixed), does it affect to battery charging process?

    Thanks & Best Regards,

    Giang
  • 0 in reply to Truong Giang
    TI__Guru 65846 points
    Hi Giang
    The 237k will prevent battery detect but when battery is installed the 10k is required to start charge. Do you have some way connect the 10k when battery is installed?
  • 0 in reply to Bill Johns
    Prodigy 170 points
    Dear Bill,

    I dont have any way connect 10k when battery is installed. I tried to install 237k and the charger still detect and charge battery.
    I want to make production so I need to make sure all board will work with fixed 237k.
    Please give me your advice in this case.

    Thanks,
    Giang
  • 0 in reply to Truong Giang
    Prodigy 170 points

    Dear Bill,

    I made some mistake in the previous test because of poor connections.

    When I installed 237k the charger does not detect battery. The OUT pin show 0V at battery absent state.

    When I leave the TS pin floating, the charger detect and charge battery but the time for charging longer than the case I use 10k. The OUT pin show 4.2V at battery absent state. In this case, it saves power but the CHG# pin does not pull to GND when charging. CHG# is important in my firmware.

    If we can't solve this problem, I'm looking for alternative part which works with low power in battery absent state. The package of the part must be as small as possible. Do you have any recommendation?

    Thanks,
    Giang

  • 0 in reply to Truong Giang
    TI__Guru 65846 points

    Hi Giang

    With only the 237k resistor connected to TS pin, the battery voltage should go to 0V and input current should be low.  This is what you are seeing.

    But when the battery is connected unit should NOT start charge with the 237k resistor.  The TS pin would need the 10k resistor connected to start charge.  This sounds different from the test results you are seeing.

    The /CHG pin will indicate the first charge cycle, will not indicate recharge. /CHG will be low for the first charge cycle but remain off if the battery voltage drops and recharge is needed.  If power to the charge is cycled the /CHG will return to first cycle condition.

  • 0 in reply to Bill Johns
    TI__Guru 65846 points
    Hi Giang
    The challenge in locating a charger that does not have a battery detection routine is how to detect when the battery has been inserted and unit should not apply voltage to the battery. All of our converters have a detection routine.