A Unified Amplifier-Based CC-CV Linear Charger for Energy-Constrained Low-Power Applications

This brief presents a linear charger architecture based on a single amplifier for regulation and the charging phase transition from the constant-current (CC) phase to the constant-voltage (CV) phase. The proposed unified amplifier is based on stacked differential pairs that share the bias current. Its current-steering property removes multiple amplifiers for regulation and the CC-CV transition, and achieves high unity-gain loop bandwidth for fast regulation. The proposed charger with the maximum charging current of 25 mA is fabricated in 0.35μm CMOS process. While the unified amplifier is biased with 20 μA, the charger achieves a peak charger efficiency of 94% and average charger efficiency of 88% with an 80-mAh Li-ion polymer battery.