Sub-50-mV Charge Pump and Its Driver for Extremely Low-Voltage Thermal Energy Harvesting

Low-voltage charge pump (CP) and its dedicated multi-stage driver (DRV) for sub-50-mV energy harvesting are proposed. The proposed DRV utilizes the output voltages of each CP to efficiently boost the control clock signals. The boosted clock signals are used as switching signals for each CP and DRV to turn switch transistors on and off. Moreover, reset transistors are added to the DRV to ensure an adequate non-overlapping period between switching signals. Simulated results demonstrated that (i) the proposed DRV can generate boosted clock signals of 712.6 mV from input voltage of 100 mV and (ii) the multi-stage CP can generate output voltage of 702.5-mV. Peak efficiency of the CP is 42.9%. The proposed CP and DRV can operate at extremely low voltage of 41 mV.