A High-Precision, Low-Temperature Drift Relaxation Oscillator Design

This paper presents a new relaxation oscillator designed as a phase-locked loop reference frequency. The conventional relaxation oscillator is a low-temperature-drift simple structure relaxation oscillator, which is susceptible to temperature-induced fluctuations in the output frequency. To address this issue, a feedback loop is incorporated into the conventional oscillator structure and a frequency sampling module is employed to sample the frequency signal. The sampled voltage is then fed back to the operational amplifier port for feedback comparison. When the system temperature changes, the sampling voltage can be stabilised near the reference voltage. Once the system is stabilised, the output current from the operational amplifier is fed back to the oscillator to compensate for frequency. This structure eliminates the need to consider the effects of the comparator offset voltage. Ultimately, its stability is only affected by resistance and capacitance, and not by temperature. The innovation of this paper is the simplicity of the structure and the low sensitivity of the frequency to temperature and voltage compared to the conventional structure. In this paper, a high-precision, low-temperature-drift relaxation oscillator is realised using a 0.11-micron process. Simulation results show that the output frequency is 10 MHz with a supply voltage of 1.2 V and a power consumption of 198 μW. The temperature coefficient of the output frequency is 41.04×106/°C over the temperature range of −40 °C to 150 °C, and the variation of the output frequency is less than 0.15% over the supply voltage range of The output frequency is also very low over the temperature range of −40 °C to 150 °C, and over the supply voltage range of 0.9 V to 1.8 V.than 0.15 %.