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BQ24195L: Never detects a charger

Anthony Hefner0
Prodigy 120 points
Part Number: BQ24195L

Hello,

I'm using an Arduino MKR GSM 1400 board, which has a BQ24195L charger circuit. I installed the jumpers to connect the D+/D- lines to the charger chip. It reliably detects when I am connected to a USB host (REG08[7:6] = 01), sets the input current limit to 100mA, and then transitions to HIZ. I have an interrupt handler installed that takes it out of HIZ, so I can detect when it is disconnected and plugged in again. But no matter what charger I connect, it always reports power good and unknown (REG08[7:6] = 00). All of the chargers appear to have D+/D- shorted, one of them explicitly says it supports BC 1.2, and I even tried cobbling up a cable that directly shorted the D+/D- lines, but nothing ever reports adapter (REG08[7:6] = 10). Does it interfere with detection if the D+/D- lines are connected to the D+/D- of the microcontroller in addition to being connected to the charger chip? Or is there something else I'm missing?

Thanks,

Tony

  • 0
    TI__Guru**** 165886 points

    Anthony,

    The D+/D- lines are only active for about 1s following VBUS power up.  If they are connected to a USB BC1.2 power source, they detect the power source minimum output current (e.g. 100mA for SDP) for initial system power up and sets in the input current limit I2C register to that value.  At that point, per the BC1.2 spec, your host software is expected to perform USB enumeration, in order to identify the USB port's actual power level and then changes the charger's input current limit via I2C spec.  If the source is a wall adapter, the D+/D- lines are shorted inside the adapter and the charger sets the input current limit to the maximum, limited only by the ILIM pin resistor clamp.  The microcontroller cannot access the D+/D- lines during the first 1-2S after charge power up.

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Prodigy 120 points

    I understand that's how it should work from the datasheet, but I'm not seeing that behavior. I tried adapters with D+/D- shorted, and I even tried shorting D+/D- directly, but the chip never reports an adapter and it sets the input current limit to 100mA no matter what I plug in. I also tried re-running the DPDM detection by setting the DPDM_EN bit in REG07 and waiting for it to go back to 0. When I'm connected to an adapter, it always reports 'unknown'. When I'm plugged in to a USB port, it always (correctly) reports USB. I've double-checked my connections. Is there any other cause you can think of for the behavior I'm seeing? Does it matter that I've disabled the watchdog to stay in host mode? Any thoughts are appreciated.

    Tony

  • 0 in reply to Anthony Hefner0
    TI__Guru 57341 points

    Tony,

    Before the VBUS is powered, are there any SYS load and/or VBAT voltage present?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Guru 57341 points

    Tony,

    We haven’t heard back from you for a while, the thread is considered solved and closed.

    Thanks,

    Ning.