LAUSR

An ultra-low-power oscillator with 0.24 pJ/cycle energy efficiency is presented, suitable for nanowatt-level energy harvesters. The sub-pJ/cycle energy efficiency is comparable with the lowest energy per cycle costs of prior arts and is achieved by minimising short-circuit current with a leakage-based delay cell and minimising dynamic power consumption with a capacitively coupled stacked structure. The proposed oscillator is fabricated in 180 nm CMOS process. Under 2.2 V supply voltage, the energy per cycle is 0.24 pJ/cycle over a frequency range of 18.2–226 kHz.