A 60 mV Input Voltage, Process Tolerant Start-Up System for Thermoelectric Energy Harvesting

This paper presents a 60 mV input voltage start-up system for thermoelectric energy harvesting. A new process tolerant inverter cell is proposed, which is functional at supply voltages as low as 60 mV. Using the proposed unit cell, a ring oscillator has been implemented. The ring oscillator is followed by 40 charge-pump stages, an ultra-low-power level detector, and a boost converter. The energy harvesting system can generate an output voltage of 1 V and delivers a maximum power of 4.5 μW from a 60 mV supply. This system has been implemented in a standard 0.18 μm CMOS technology, uses neither zero-threshold voltage (normally-on) negative-channel metal-oxide semiconductor nor microelectromechanical systems switches and occupies 3.3 mm
²
.