Switched-Capacitor Voltage Buck Converter with Step-Down-Ratio and Clock-Frequency Controllers for Ultra-Low-Power IoT Devices

This paper presents an ultra-low-power switched-capacitor (SC) voltage buck converter (VBC) with step-down-ratio and clock-frequency controllers for ultra-low-power IoT devices. The proposed VBC consists of an n/8 SC VBC, step-down ratio controller, clock (CLK) generator, load current monitor, local VDD generator, and output voltage monitor. The step-down-ratio controller monitors an input voltage and then changes the step-down ratio n/8 of the SC VBC according to the input voltage ( n = 5,6,7,8). This enables the SC VBC wide input voltage operation. The CLK generator with the load current monitor changes an operating clock frequency in accordance with the load current to achieve highly efficient power conversion. Simulation results demonstrated that our proposed VBC converted 1.4-2.4 V input to 1.33-1.57 V output. The power dissipation at the steady state was 14.6 nW.