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BQ24272 - missing info

1886332
Expert 1325 points
Other Parts Discussed in Thread: TPS3831

Hi,

Assuming having the below inputs:

VBAT is set to 4.0V

IBAT = 325mA

Isys = 1.25A

So Isw = IBAT+Isys=1.575A

 

  1. What is the voltage Vsys – Is it VBAT + 3% -> ~4.1V
  2. What is min VIN which can be used in this condition?
  3. I do not see any efficiency parameter -> What is Iin at these condition?
  • 0
    TI__Guru**** 154236 points

    Regarding 1, the battery FET during charging is on so VSYS = VBAT + IBAT*RDSON(BATFET).

    Regarding 2, the minimum VIN for full 1.575A will be determined by the efficiency of the charger as well as the series resistance of line.  Attached is a paper that might help explain. 

    Regarding 3, efficiency for condition will be close to 90-92%.

    VIN_DPM app note _ mod.docx
  • 0 in reply to Jeff F
    Expert 1325 points

    Hi Jeff,

    Thank you for your great answer.

    one more thing:

    We need to monitor the Battery voltage and alert when it reaches 3.1V

    Is there a way to monitor the Battery voltage (during Input fault while Battery is discharge)

    I didn't find a register which give the battery voltage

    thanks

  • 0 in reply to 1886332
    TI__Guru**** 154236 points

    The charger does not have a integrated ADC and so does not monitor battery voltage.  For battery voltage, current and health monitoring, you could use a battery gas gauge.  Or, if monitoring that one voltage is all you need, you could use a voltage supervisor like TPS3831.