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BQ25890: Vsys output issue related to Input Current Limit setting

Anthony Yoo68
Expert 1320 points
Part Number: BQ25890

Hi

My customer uses BQ25890 to supply Battey Charging and System voltage.

Customer's circuit configuration is shown below.


However, when 12V is input to the Vbus using the quick charger (Quick Charging 3.0), there is a problem that the Vsys voltage is not outputted at 4.2V.

When comparing the register values ​​before and after the problem, it is confirmed that the BATFET_DIS bit of REG09 changes from 0 to 1 when a problem occurs.

Repeating the problem can be reproduced easily by repeatedly plugging and unplugging the charger.

At this time, I also confirmed that Iinlim 2.4A (0x5c) of Reg00 is set automatically.

On the circuit, the setting resistance of the Ilimt pin (pin 10) is connected to Ground at 240 ohms.

We have done various tests to improve the problem and have confirmed that this problem does not occur when changing the ILIMT (10 pin) resistance to 240 -> 0 ohms.

And I confirmed that the problem is reproduced equally from the resistance value of 240 ohms to 50 ohms.

How does this problem relate to the setting of ILIMT (10 pin)?

If Ilim EN of REG0 is set to "1", is it the right setting for 10 pin setting to 0 ohm?

In addition, the register values before and after the trouble occur are attached as follows.


Please help me.

Thank you.

Best Regards.

 

From Anthony.

  • 0
    TI__Guru 57621 points
    Anthony,

    1.When ILIM pin is short, the input current limit is set by the register.
    2. What is ISYS profile? Please note that when the system is overloaded or shorted (IBAT > IBATFET_OCP), the device turns off BATFET immediately and set BATFET_DIS bit to indicate BATFET is disabled until the input source plugs in again or one of the methods describe in BATFET Enable (Exit Shipping Mode) is applied to re-enable BATFET.

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.
  • 0 in reply to Ning T
    Expert 1320 points

    Hi

    Thank you for your reply.


    As already mentioned, we do not have a problem with Vsys voltage off when HW input current limit (pin 10)pin is cut off with the ground and SW input current limit (REG00) is only enabled (6 bits).

    Here are some questions.

    1. When the HW pin is set to a resistance value (400 to 50 ohm) instead of cutting off the ground, there is a problem with the Vsys voltage dropping as it is now. Can you guess why?
    You asked me to check the Ibat current, but before that, when you set it to SW input current reset, there is no problem, and I do not understand that it is only a problem when you set the input current reset of the HW pin.

    Can you give me your opinion on this?

    2. Is it correct to set the SW input current limit automatically according to the input source type?
    If I try to set a random input current limit, is there any problem if I write the 5-0 bit value of the REG00 register at my disposal?

    3.Is it the correct setting for me to ground and shunt HW pin(pin 10) and set the Input current limit only for SW(REG00)? Is there anything wrong with this setting?

    4. In conclusion, if the problem is not caused by shorting the HW pin to ground and setting the input current limit to the SW register (REG00), we will choose that method. But I just want to see why setting the input current limit at the same time as the HW pin to eliminate its side effect.
    please check it.
    Thank you
    best regards
    From anthony

  • 0 in reply to Anthony Yoo68
    TI__Guru 57621 points
    Anthony,

    1. The recommended maximum input current limit is 3.25A. The ILIM resistor chosen should not beyond the range.
    2. Once the initial input current limit detection is complete, users may modify the input current limit by REG00[5:0]) via I2C.
    3. It is ok to short ILIM pin to ground, the input current limit is set by the register.
    4. We haven't observed the behavior described by you. Have you tested on the BQ25890 EVM?

    Thanks,

    Ning.