The BQ2416xx provides an integrated, fixed-frequency 1.5-MHz voltage-mode controller to power the system and supply the charge current. The voltage loop is internally compensated and provides enough phase margin for stable operation, allowing the use of small ceramic capacitors with low ESR. When starting up, the BQ2416xx uses a "soft-start" function to help limit inrush current. When coming out of High Impedance mode, the BQ2416xx starts up with the input current limit set to 40% of the value programmed in the I²C register. After 80 ms, the input current limit threshold steps up in 256-µs steps. The steps are 40% to 50%, then 50% to 60%, then 60% to 70%, then 70% to 80%, and finally 80% to 100%. After the final step, soft start is complete and will not be restarted until the BQ2416xx enters High Impedance mode.

The input scheme for the BQ2416xx prevents battery discharge when the supply voltages are lower than VBAT and also isolates the two inputs from each other. The high-side N-MOSFET (Q1/Q2) switches to control the power delivered to the output. The DRV LDO provides a supply for the gate drive for the low side MOSFET, while a bootstrap circuit (BST) with an external bootstrap capacitor is used to boost up the gate drive voltage for Q1 and Q2.

Both inputs are protected by a cycle-by-cycle current limit that is sensed through the high-side MOSFETs for Q1 and Q2. The threshold for the current limit is set to a nominal 5-A peak current. The inputs also utilize an input current limit that limits the current from the power source.