The BQ24075 charger starts the charging sequence if the following conditions are met
- a. VIN > VUVLO (maximum 3.4V)
- b. VIN > VBAT + VIN(DT) ( VBAT + 0.13V max)
We have the following input operating conditions
I. Minimum input voltage is 4.3V when powered from adapter
II. Minimum input voltage is 4.75V when powered from USB
III. Input voltage is 3.4V to 4.2V when powered from another accessory
We have tested the BQ24075 and found the following observations
When the input voltage is 3.9V,
- VOUT=3.9V
- VBAT=3.3V
- /PGOOD status output is LOW
- /CHG status output is LOW
Charging is not happening actually when the input is 3.9V but the /CHG status is LOW indicating charging is happening. Please refer the below waveform for the above condition. The above condition exists up to the input voltage range 4.3V. When the input voltage reaches 4.3V, the charging current starts from few milliamps and reaches the programmed charging current 500mA at 4.45V. The output voltage VOUT is maintained at 4.3V over the input range 4.3V to 4.45V.
As per the Figure 40, the charger should charge the battery in fast charging mode after /CHG status goes low when the input voltage VIN > VBAT + VIN(DTmax) = 3.43V. Please let us know why the charging is not happening when the input voltage is below 4.3V.
