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BQ25890: bq25890 can not charge normal when use unknown 12V adapter

Zhihu Liang
Prodigy 20 points
Part Number: BQ25890

We use this chip for a product that has only 12V (adapter) input and 12V output.  Because the adapter is a common adapter 12V/2A, so the input current limit will set to 400mA automatically. And then the charger chip could charge the battery(1s2P, 7000mAh) well. We think it is too slow to charge the battery. So we use I2C set the input current limit to larger than 600mA like1A (REG00, 0x54 ). The charger chip can not charge the battery. And the waveform is like this.

If I use a DC power supply to adjust the input voltage to below 7.5V, then the charger works well.  Does anyone know how it happens? What should I do now?

  • 0
    TI__Guru**** 154276 points
    Hi Zhihu,

    If lowering the power supply voltage to 7.5V results in charge restarting, it appears that you are in VINDPM. At startup, the charger defaults to relative VINDPM mode. In relative mode, the charger automatically sets the VINDPM threshold to 600mV below the detected VBUS voltage at startup. Register 0D[0:6] reports this value. If the voltage at VBUS starts to drop below this threshold, the charger reduces input current limit (and therefore charge current) to prevent VBUS from drooping below the threshold. You force a VINDPM voltage by set REG0D[7] to 1 and then writing your own VINDPM threshold into REG0D[0:6].

    Is the 12-V adapter QC2.0 compliant? Do you have HVDCP enabled (REG02[3]?
  • 0 in reply to Jeff F
    Prodigy 20 points
    Thank you for your quick reply. I have try a lot on set the REG value.
    The 12-V adapter dose not support QC2.0. So I do not want for HVDCP handshake. And no matter what value I set for REG02[3], the result has no different.
    I have set the VINDPM to absolute value in REG0D to 0x8D, it has no different. I could start charge no mater what I set when the input voltage is 5V. And then, I try to adjust the voltage to 12V, it is normal when the voltage goes high, the pulse width gose narrow. Untill the voltage is close to 12V, it suddenly change to like in the post.