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BQ24650: What will happen if the input to the BQ24650 is accidentally the battery?

Derek
Mastermind 9792 points
Part Number: BQ24650

Hello,

   We have a device that has three possible power sources:

External AC-DC power supply

Solar Panel

LiPO4 battery

These are going through a power prioritizer in that order. The output of this is feeding the system as well as a BQ24650 battery charging circuit. I do have a large diode on the input to the battery charging circuit, but what would happen if the prioritizer switches to the battery, so the battery output is trying to charge the battery?

  • 0
    TI__Mastermind 24075 points

    Hi Derek,

    There is no issue if the battery voltage is fed back as VCC (input voltage) to the BQ24650 as the charger will be in a suspend mode. The diode on the input to the battery charging circuit, means that even if the battery voltage is selected as the input, the VCC (battery voltage - fdw V diode) of BQ24650 will be < than measured SRN (actual battery voltage). This condition satisfies SLEEP for which specific threshold is mentioned in the EC table.

    BQ24650 uses a SLEEP comparator to determine the source of power on the VCC pin, because VCC can be supplied either from a battery or an adapter. If SRN voltage is greater than VCC, indicating that a battery is the power source, the BQ24650 enters low quiescent current (< 15 µA) SLEEP mode to minimize current drain from the battery.

    Essentially if your prioritizer switches input of BQ26450 to battery, there is no harm but you also will not charge the battery in any way.