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BQ76920: BQ76920 REGOUT current

hwswdesign
Intellectual 310 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ78350-R1

If I use  BQ76920 with its REGOUT powering a BQ78350-r1 and other circuitry, up to the REGOUT current limit of 20mA, is that factored into the state of charge? I would guess that it's not, and that 20 mA would create an error, wouldn't it?

  • 0
    TI__Guru 54715 points
    The gauge current typically returns to the low current ground inside the sense resistor and is not included in the coulomb counting. The bq78350-R1 has a parameter to compensate for a self discharge which is not gauged, this should be set to compensate for the electronics current (IDD, REGOUT and any other supplies), cell self discharge, and model for the dynamic useage such as LEDs. When setting a budget for the REGOUT current, remember to include the gauge's infrequent flash update current from its datasheet. When modeling the LED current pick an expected useage rate, certainly the real rate could vary between a user who never activates the LEDs and one who continuously presses a display button. See the bq78350-R1 Technical Reference Manual page 66 "Self-Discharge Rate" parameter. If you set the parameter too high the battery reports empty early, if you set it too low the battery will terminate while it still shows capacity.
    The experts at the gauge forum will be better able to assist if you have gauge questions.