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BQ24075: Battery charger is active while connected to USB but not while connected to external power supply

PATRICK OHARA
Genius 3205 points
Part Number: BQ24075

Hello,

I'm using the BQ24075 battery charger as part of a USB-to-UART interface to a CC2640r2 BLE system. I've configured the BQ24075 to source a maximum of 100mA. I've configured the load to draw 25 mA and in another case 250mA for test purposes. While connected to a USB port on my computer the charger operates and provides current to the battery to charge and the load to a maximum of 100mA - all good. However, when I use my Keithley 2281 power supply/battery simulator to provide 5VDC up to 1.0A the BQ24075 no longer charges the battery. The CHG status is high indicated that charging is inactive. PGOOD is low indicating that the power is good. When I switch back to the USB port the BQ24075 charges the battery again with either load. Is there a reason why the device operates this way? Can someone suggest a way to make the BQ24075 charge the battery regardless of being USB or externally powered?

Thanks,

Patrick

  • 0
    Genius 3205 points

    It turns out that the problem is not with the TI BQ24075. Rather, the problem is with the SiLabs CP2102N USB-to-UART transceiver. Because I mis-wired the CP2102N, it did not correctly identify the difference in sources, USB port vs AC adapter. The result was that the the enable pin on the BQ24075 was hi (device disabled) while connected to the AC adapter, and the BQ24075 was enabled during USB operation. Mystery solved.

    Patrick