“…Previously proposed highly accurate CMOS oscillators include RC relaxation oscillators [1,2], mobility-based oscillators [3], ring oscillators (RO) [4,5,6,7,8,9], LC oscillators [10] and RC harmonic oscillators [11]. Among these oscillators, the RO is one of the research hotspots because of its superior in low circuit-complexity and convenient frequency-tunability [12]. In deep submicron process, the temperature-drifting propagation delay of logic gates makes the RO a difficult solution for frequency reference design.…”