A 55nA Quiescent Current Power-Wise Buck Converter With 1μA–600mA Load Range and 0.5V–1.8V Flexible Output Voltage Options

This paper presents an ultra-low quiescent current power-wise buck converter for portable devices. To achieve high conversion efficiency across a wide range of load currents while minimizing the output ripple, the converter utilizes pulse-width modulation (PWM) and pulse-frequency modulation (PFM) control methods in heavy load and light load conditions, respectively. Time-division power supply technique is implemented to reduce the quiescent current. The converter incorporates an 8-bit built-in digital-to-analog converter (DAC), allowing selection of 256 different output voltages ranging from 0.5V to 1.8V in 5mV steps. Additionally, a transient enhancement circuit is included to expedite the transient response during mode switching. Fabricated in $0.18\boldsymbol {\mu }$ m CMOS process, the proposed converter is capable of handling load currents from $1\boldsymbol {\mu }$ A to 600mA with an input voltage of 2.5V to 5V. Featuring an ultra-low quiescent current of 55nA, the converter achieves a peak efficiency of 94.1% and maintains greater than 85% efficiency over a load range of $10\mu $ A to 500mA when input and output are 3.6V and 1.8V, respectively.