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BQ24172 - Internal Voltage Regulator for battery and AC input

Hiram Hoffman
Prodigy 10 points
Other Parts Discussed in Thread: BQ24172
My design incorporates two (2) Li-ion,AA, 3.7V batteries. Each with a 2200mAh capacity serving as a power source when the device is not plugged in to the 12V main supply.
 
From my browsing of the datasheet it seems like I can set the bq24172 to regulate the battery voltage to the load.
 
So in my application, instead of blasting the system load with the entirety battery combined voltage of 7.4V I want to be able to dial it down to the system at 6V.
 
I also want to be able to supply the system with a regulated 6V from the 12V DC charging source when its plugged in and I believe I can achieve that with the internal regulator in the chip.
 
Essentially what I want, is to be able to provide the system with 6V power all the time irregardless of whether the battery is supplying the power or whether the 12V charging source is plugged in. I've search for an application circuit to do this but I can't find one. How would I go about this?
  • 0
    TI__Genius 13700 points

    Hello Hiram,

    There is no regulator internal to the device that can operate in the way that you laid out in your post. The regulators present on the device such as the output of Vref would be insufficient to run your system. The buck converter that is present is used explicitly to take the input voltage and regulate it to effectively charge the battery.

    The simplest solution would be to take a two stage approach and attach a buck converter on the line to the system seen in the datasheet schematics. This would then buck the voltage to the system down to the desired 6V regardless of whether it is 12V coming from your adapter or some other voltage coming from the battery.