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BQ25890: BATFET out of control?

andres_dalmati
Expert 1110 points
Part Number: BQ25890

Hi,

I made my own device with a TM4C123G and bq258090 following the design recommended by the webench.

The equipment works well if the battery is the only power source connected. I can read the values of voltage, temperature, etc. When I connect the adapter the problems start.

1st - Once the adapter is connected to the USB of the PC, the first 4 interruptions occur (plug in, poor source qualification, source type detection, and VINDPM Threshold). I see them with the oscilloscope (apparently normal). It detects the adapter well (SDP), The STAT LED is ON, but..... Ibat reads are always 0mA. but after a certain time, around 40s, the Vsys drops to 0V.
I am a little lost with respect to the cause of this, because I understand that the only reason for this would be entering the shipping mode, which is certainly not the case.

2nd - Today to make this post, I wanted to repeat the experience following the same steps and something totally new came up. The CH2 is the output of a regulator that the input is Vsys, CH1 is the INT pin. I can't repeat the previous situation. Apparently there are 3 interrupt before the shut down, but I cannot read the registers because the connection is broken when the power is OFF.

The only different from yesterday is that I had changed the battery with an external device.

Thanks in advance

Andrés

  • 0
    TI__Guru**** 166776 points
    Andres,

    It appears that the SDP input source is collapsing. It cannot provide enough power to supply both the load on SYS and charge the battery. Can your power source provide 500mA? What is the voltage at the charger's VBUS pin when this happens? What is the load on SYS? How much charge current are you requesting (i.e. what is the resistor on ILIM, if enabled, or what is the value in the charger's charge current register?)
  • 0 in reply to Jeff F
    Expert 1110 points

    Hi Jeff,

    It is the usb of the PC, I think it does not collapse and can deliver at least 500mA. When I power it with a 5V regulated power source, after pulling 30mA (Ibadsrc) it powers down Vsys during aprox 100ms, as shown in the 2nd picture. It repeat this process every half a second and then it powers off Vsys definitely until the usb plugin off on again.

    the voltage at the charger's VBUS pin when this happens is 5V.

    The load on SYS is aprox 250mA. The battery is fully charge (4.2V). the resistor on ILIM is 221R. Always read 0mA

  • 0 in reply to andres_dalmati
    TI__Guru**** 166776 points
    Andres,

    A minimum of 8.2uF of capacitance is required on PMID, which is the input to the buck converter. Can you try adding that capacitance? If the same error, then can you send your register settings after the first power off?