JAJSFS8 July 2018 BQ25601D
After the input current limit is set, the converter is enabled and the HSFET and LSFET start switching. If battery charging is disabled, BATFET turns off. Otherwise, BATFET stays on to charge the battery.
The device provides soft-start when system rail is ramped up. When the system rail is below 2.2 V, the input current is limited to is to the lower of 200 mA or IINDPM register setting. After the system rises above 2.2 V, the device limits input current to the value set by IINDPM register.
As a battery charger, the device deploys a highly efficient 1.5 MHz step-down switching regulator. The fixed frequency oscillator keeps tight control of the switching frequency under all conditions of input voltage, battery voltage, charge current and temperature, simplifying output filter design.
The device switches to PFM control at light load or when battery is below minimum system voltage setting or charging is disabled. The PFM_DIS bit can be used to prevent PFM operation in either buck or boost configuration.