A 47-nA Quiescent Current Dual-Mode Buck Converter With Fast Load Transient Response From Ultra-Light Load Mode

This brief proposes a dual-mode ultra-low quiescent current buck converter that achieves high efficiency over a wide load range. The system employs adaptive on-time control (AOT) for heavy load and adaptive clock control (ACC) for light load. To enhance transient performance under light load, a fast clock frequency locking (FCFL) circuit is proposed to enable quick load tracking with simple digital logic. Additionally, a nA low-power load step transient enhancement (LSTE) circuit is presented, effectively reducing overshoot and undershoot during load transients. The converter is implemented in a 0.18 μm process and operates with an input voltage of 2.4 V to 3.3 V and an output of 1.6 V. The load current ranges from 500 nA to 300 mA. The total quiescent current is 47 nA contributed to ACC digital control and it achieves 87% efficiency at 1 μA load current, with a peak efficiency of 95.9% at 2.4V input. It achieves an undershoot voltage of 60 mV with recovery time of 6 μs when load current switching from 100 μA to 100 mA.