A nW-Level Low-Power Digital-Controlled Frequency Source Circuit for IoTs Application

This paper presents a subthreshold nano-watt digitally controlled oscillator (DCO) targeting ultra-low-power applications in IoT wireless sensor networks such as ambient energy harvesting systems and wake-up radios. The key innovation lies in a subthreshold current-steering array integrated within the comparator, which dynamically adjusts the bias current across different oscillation frequencies to simultaneously optimize both power consumption and phase noise performance. The proposed oscillator achieves a wide frequency tuning range from 20 kHz to 660 kHz through eight discrete steps with 80 kHz resolution, while maintaining ultra-low power consumption of 51 nW to 274 nW at a 0.9 V supply voltage. The simulation results demonstrate excellent phase noise performance of better than -85 dBc/Hz across the entire operating frequency range.