JAJSHF0B February 2019 – November 2019 BQ25887
PRODUCTION DATA.
After the input current limit is set, the PG pin is pulled LOW, the PG_STAT and VBUS_STAT bits are changed, and the converter is enabled, allowing the QHS and QLS to start switching. Before charging begins, the battery discharge source (IBAT_DISCHG) is enabled automatically to detect the presence of battery. The host can enable IBAT_DISCHG via the EN_BAT_DISCHG bit at any point during operation, including in Battery Only or HIZ modes. The device provides soft-start when converter output voltage is ramped up.
As a battery charger, the device deploys a highly efficient 1.5-MHz boost 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.
In order to improve light-load efficiency, the device switches to PFM (Pulse Frequency Modulation) control at light load when battery is below 6.4V or charging is disabled. During the PFM operation, the switching duty cycle is set by the ratio of SNS and VBUS.