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BQ24161: Unstable Charging Current State of BQ24161

user5891465
Prodigy 80 points
Part Number: BQ24161

When I use BQ24161 to set charging current above 1A, I will encounter unstable charging current, sometimes normal current, but most of the time is about 500 mA, using a single cell of 4.2V/2000 mA, using USB and external DC9V power supply, battery voltage has been charging at 500MA from 3.5 to 3.8V, charging from 0V to 3.3V is normal. How to deal with it?

In addition, can the output of SYS voltage be constant when charging? What's found now is that it changes with the voltage of the battery?

  • 0
    TI__Guru**** 150315 points
    Hi,

    TI charger's power path/NVDC topology ensures that the SYS output never drops below the minimum system voltage but follows the battery as it charges, once the battery voltage exceeds the system voltage.

    Regarding the charge current, can you send a schematic? Which input are you using? What is the input current limit for that input? If USB, the PSEL pin sets the input current at startup. If the input current is limit is not high enough to support the load on SYS and battery charge current, battery charge current reduces and could even reverse in order to supply the system with enough current. What is the VINDPM setting?
  • 0 in reply to Jeff F
    Prodigy 80 points
    hi,
    We require that both channels (USB/IN) can be input, 5V for USB, 9V for INPUT, 500mA for USB charging current, 1500mA for IN charging current, and 4.2V for VINDPM.
  • 0 in reply to Jeff F
    Prodigy 80 points

    Hello, thank you for your previous reply, BQ24161B this chip has been tested by the R&D department for many times. It is found that this chip does not work properly when the IN port is connected to the 9V voltage input. The charging current cannot be adjusted, and the charging and discharging are frequently repeated to 3.6. V automatic cut-off charging phenomenon, the chip will automatically reset and restore the default parameters during use, and I2C communication will be interrupted; instead, it can work normally when the IN port is connected to 5V-5.5V voltage input. The experimental result is described in the chip specification. Non-conformity, the specification stated that the IN port of the BQ24161B can support a maximum of 10.5V. I hope you can give us doubts, thank you.
    The following is our experimental phenomenon: BQ24161B after burning the software version with the power adapter (specification 9V 1A, 9V 2A) the first charge can be charged to full power, but unplug the power adapter, discharge without removing the battery To low battery (about 3.5V), when charging again, the power will only charge to about 3.6V to stop charging, and at this time, the I2C of BQ24161B will interrupt communication, and the chip will automatically reply to the default parameters. The charging current parameter is set to 1950mA, and the charging current is detected by the DC power generator. The charging current of the BQ24161B is about 300mA at 9V, which does not change with the setting of the charging current parameter. When the voltage is adjusted to 8V\7V, the change is still small. When the voltage is adjusted to 6.5V, the current changes to 400mA. When it is adjusted to 5V to 5.5V, the current suddenly becomes about 2A, and this voltage input, the set charging current parameter is consistent with the actual, and can be adjusted.

  • 0 in reply to user5891465
    TI__Guru**** 150315 points
    Hi,

    If the watchdog timer expires due to no I2C communication, the charger resets its registers to default, including VBATREG=3.6V.

    Can you send oscope shots of the voltage at IN, BAT, battery charge current and SW when IN =9V? Is the charger's input current limit set to match that of your 9V input source or is the charger collapsing the power source? What device is simulating the battery?
  • 0 in reply to Jeff F
    TI__Guru**** 150315 points
    Hi again,

    I have been testing on the bench and I am able to charge up to 10V on IN. There is an issue with softstart at IN=9V for about 10ms roughly 100ms after power up but no other anomalies. Are you able to read the I2C registers during or after the failure? If so, what faults does the charger report? Also note that if the safety timer expires, the registers reset to default.
  • 0 in reply to Jeff F
    Prodigy 80 points

    Hi,

    9V is provided by DC power supply. The specification of the battery is 3.7V/2000mAH, and the full charge is 4.2V. I will give you a picture of the battery charging current and the IN port voltage and SW voltage. The charging current parameter is 1450mA. The SW screenshot is the IN port 9V input. The external MCU reads and writes I2C every 500ms, and writes the setting parameters to the BQ24141B repeatedly. However, after the fault occurs, the I2C register cannot be read. When the battery is charged to 3.6V, the battery is turned off.Experimental picture.rarExperimental picture.rar

  • 0 in reply to user5891465
    TI__Guru**** 150315 points

    Hi,

    Below is a scope shot of the BQ24161B EVM operating at your conditions.  I have input current limit = 2.5A and VBATREG=4.2V.  The only non-ideal operation that I see is a brief oscillation in current during soft start.  Can you capture your fault in scope shot similar to this?

  • 0 in reply to Jeff F
    TI__Guru**** 150315 points

    The scope shot did not cut and paste properly so here it is attached.

  • 0 in reply to Jeff F
    TI__Guru**** 150315 points
    Hi,

    Were you able to take a scope shot of charger startup, similar to the one shown above?
  • 0 in reply to Jeff F
    TI__Genius 10240 points
    Hi there,

    We haven’t heard back from you. We are assuming you were able to resolve the issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.