A Sub-nW 32-kHz Crystal Oscillator Architecture Based on a DC-Only Sustaining Amplifier

This article introduces a novel oscillator architecture that enables sub-nW power consumption in a 32-kHz crystal oscillator (XO) by amplifying the oscillation signal at dc, instead of the oscillation frequency. The impact of circuit nonidealities on the oscillator's performance is analyzed. Measurement results of 20 different 65-nm standard CMOS dies show an average power consumption of 0.55 nW drawn from a 0.5-V supply at room temperature for a 32-kHz XO. The measured long-term stability of the XO is 14 ppb. The proposed oscillator architecture does not require any calibration schemes or multiple supply domains.