A Wide Load Current and Voltage Range Switched Capacitor DC–DC Converter with Load Dependent Configurability for Dynamic Voltage Implementation in Miniature Sensors

Abstract

Advancements in low power circuits and batteries have enabled the design of miniature sensors with tiny batteries. In such systems, implementing dynamic voltage scaling (DVS) is crucial for maximizing system lifetime. In this paper, a new switched capacitor (SC) converter that is capable of handling a wide range of load currents and output voltages is presented for on-chip DVS implementation. The proposed converter consists of multi-ratio multi-leaf SC stages and reconfigurable interconnect, enabling fine voltage resolution. The stage interconnect scheme enables cascaded or parallel connection of stages. The multi-leaf structure allows load-dependent switch size selection, offering a better trade-off between losses over a wide load range. A limited-voltage-swing switch-driving scheme allows efficient down-conversion from high battery voltage input. A prototype was fabricated in a 180 nm process, providing an output voltage with effective resolution of 16 mV over a load current range of 300 nA to 300 μA (1000×) from a 4 V battery. Efficiency greater than 62% and a peak efficiency of 77% are achieved under a light load (500 nA) over a voltage range of 400 mV to 1.6 V. Efficiency greater than 64% and a peak efficiency of 72% are achieved under a heavy load (200 μA) over a voltage range of 700 mV to 1.6 V.

Keywords

• switched capacitor circuits
• DC–DC converter
• dynamic voltage scaling
• internet of things
• wireless sensor network
• low power electronics