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BQ25181: Regulated System Output with 3.7V Battery

Dave Moore
Prodigy 20 points
Part Number: BQ25181

I am looking at the BQ25181 to act as a battery charger and system voltage regulator in my wearable device. The device will be powered from a 3.7V li-po battery - will the BQ25181 still be able to provide a 4.5V regulated output on the SYS pin both when a power supply (USB) is present and when running off battery? If not, is there a single device that can do this, or will I need a charger IC and a boost converter (eg. TPS61099x)?

  • 0
    TI__Mastermind 23220 points

    Hi Dave,

    Welcome to E2E!

    The BQ25181 will only be able to regulate the SYS voltage to 4.5V (or the configured regulation setting) when a valid VIN is present. When only the battery is present, the SYS voltage will not regulate and will be

    VSYS = VBAT - VDO where VDO is RON_BAT * (IBAT) 

    There are devices that can boost the battery voltage to the system output. Do you have information such as input voltage and charge current that you can share? It'll help us find you the best device for your application.

    Best Regards,

    Anthony Pham