This document introduces a fast-charging controller IC3 that achieves efficient charging of the battery by controlling the PWM duty cycle of the switching regulator IC1, thereby improving charging efficiency.
The note explains a fast‑charge controller circuit where the external PNP transistor is replaced by a 5 A buck switching regulator (IC1). By controlling the PWM duty cycle of IC1, the controller IC3 regulates the charging current efficiently for battery packs.
Key design considerations include current sensing with R6, loop stability set by C4 at the CC terminal, and the effect of the battery filter capacitor C5 on the dominant pole. The document also references the MAX713 QuickView data sheet for further details.