A Low-Power, Differential Relaxation Oscillator With the Self-Threshold-Tracking and Swing-Boosting Techniques in 0.18- $\mu$ m CMOS

This paper presents a fully integrated, 8.2-MHz relaxation oscillator with a self-threshold-tracking loop and swing-boosting technique for improving its long-term frequency stability and noise performance. The proposed latch-based relaxation oscillator increases the transition speed to reduce the static power consumption. To decrease the process–voltage–temperature dependence, we propose a self-threshold-tracking loop to ensure that the transition point of the inverter-based comparator is set to a fixed ratio of the supply voltage. In addition, the comparator delay can be compensated by the tracking loop, relaxing the requirements of comparator power consumption. The design is implemented in a 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process. The design achieves a period jitter of 7.66 ps_rms, the phase noise of −109 dBc/Hz at an offset frequency of 100 kHz, and an Allan deviation noise floor of 1.56 ppm. The resultant figure of merit is 160.8 dBc/Hz, while only consuming 46.3 <inline-formula> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula>. The power efficiency of the design is 5.6 kHz/nW. As for the supply sensitivity, the design achieves 0.9 %/0.1 V, which is 10<inline-formula> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> lower than the design with no compensation loop. The measured temperature coefficient of the proposed oscillators is 123 ppm/°C from −20 °C to 100 °C without any trimming process.