A sub-100μW area-efficient digitally-controlled oscillator based on hysteresis delay cell topologies

This work addresses an all digitally-controlled oscillator (DCO) design with three newly proposed hysteresis delay cells (HDC). According to circuit topologies, the three HDCs are defined as on-off, cascaded, and nested HDCs that provide different propagation delay. These HDCs comprise architecture, a power-of-two delay stage DCO (P2DCO), that every delay stage provides half delay than the previous one in a descending order, resulting in low power and low cost features. A self-calibration method is accompanied to maintain the monotonicity of the P2DCO under PVT variations. The P2DCO is verified in a 90nm CMOS technology. The LSB control word provides a 2.04ps delay resolution. The post-layout simulations show that the dynamic power is 75.9μW and 5.2μW in the 239.2MHz and 3.89MHz, respectively. The area of the P2DCO is 60×20μm2.