An Efficient and Small Area Multioutput Switched Capacitor Buck Converter for IoTs

Abstract

This paper presents an area and power efficient multioutput switched capacitor (MOSC) DC-DC buck converter targeting ultra-low power and IoT devices. The MOSC converter has a variable input voltage range between 1.05V to 1.4V and generates regulated simultaneous multiple output voltage levels of 1V and 0.55V. Adaptive digital time multiplexing controller is employed to enable multiple power domains. In addition, a pulse frequency modulation is utilized to regulate the output voltages over a wide range of load current. The proposed converter supports a load current of 10μA to 350μA and to 10μA at a load voltage of 1V and 0.55V, respectively. Adaptive time multiplexing and pulse width modulation are implemented through a finite state machine to eliminate the reverse current issue. This problem arises during the switching from a low load voltage of 0.55V to a high load voltage of 1V. The MOSC circuit is fabricated in 65nm CMOS technology and it occupies an active area of 0.27mm2. Moreover, both MIM and MOS capacitors are utilized to further reduce the area of MOSC converter. Measured results shows that the peak efficiency of 78% is achieved at a load power of 300μW.