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BQ24171: Pre charging consultation

dxd1412
Prodigy 90 points
Part Number: BQ24171

Hi Jeff

        I have a few questions about pre charging that I would like to ask you, and I hope you can help me answer them

Q1：I set the pre charging voltage below 3V to start pre charging, but why does the charging current always switch over at around 2.8V. I tried "BQ24171EVM-706-15" and the same situation happened. Why is this? Is he normal?

Q2：I can switch from pre charging to fast charging in 3V, which is very smooth. But why does switching from fast charging to pre charging delay until around 2.8V before switching?

Q3：I hope you can provide me with a solution to the above problem or an explanation for this phenomenon. I need to explain it to my client

Above, looking forward to your reply

  • 0
    TI__Guru*** 146695 points

    Hi dxd,

    The pre to fast charge transition is at VBAT_LOWV.  The spec is shown below:

    The measurement is at FB pin with 100 mV hysteresis.  So if you have feedback resistors set for 4.2V, the multiplier is 2, VBATLOWV is 1.45V*2 = 2.9V typical with 100mV hysteresis down to 2.8V.

    Regards,

    Jeff