A Digitally Controlled Output Adjustable High Stability Relaxation Oscillator

In view of the problem that the output frequency stability of traditional relaxation oscillator is easily affected by the change of external conditions, a digitally controlled output adjustable high stability relaxation oscillator is designed. The oscillator uses digital signals to control the output of the bias current and the size of the capacitor in the capacitor charging and discharging loop in the relaxation oscillator, so that the oscillator is capable of adjusting the output frequency by means of digital control signals. A zero temperature coefficient current is also generated to minimize the effect of temperature on the output frequency. The overall circuit is built using SMIC 0.11μm process and simulated using Candace Virtuoso. Simulation results show that the circuit is capable of outputting a frequency signal of 10Mhz under digital signal control, and the temperature coefficient of the output frequency is 133.3ppm/°C in the temperature range of -40 °C to 125°C.