A Low Power Oscillator with Temperature Compensation

Aiming at the problem that the oscillation frequency of traditional relaxation oscillator was easily affected by temperature, and to meet the demand of low power applications. In this paper, a relaxation oscillation with low power and low temperature coefficient is designed. On the one hand, by simplifying the circuit structure of the traditional relaxation oscillator, the current comparator with simple structure is used, and the current comparator has lower power consumption than the voltage comparator. On the other hand, a self-bias structure is used to generate reference current and reference voltage, the reference current is generated by MOSFETs operating in the subthreshold region, and the reference voltage is generated by the reference current on the resistor, the power consumption of the overall circuit is reduced by using smaller reference current. Because of the comparator delay is greatly affected by temperature, the oscillation frequency of relaxation oscillator is also easily affected by temperature, so as to improve the temperature stability of the oscillation frequency, a suitable resistance positively correlated with temperature is obtained by series of resistors with positive and negative temperature coefficients, which is in the self-bias reference, to compensate for the comparator delay negatively correlated with temperature. Based on Cadence platform, the relaxation oscillator is designed using 0.18µm CMOS process. The simulation results show that under the 1.2V power supply voltage, the oscillation frequency of the relaxation oscillator is 36kHz, the power consumption is 61nW, the reference current generated by the self-bias reference is 12.5nA, and the reference voltage is 62mV. In this paper, the circuit realizes the temperature compensation of the oscillation frequency, with a temperature range of −40°C∼125°C and a temperature coefficient of 40 × 10
⁻⁶
/°C for oscillation frequency.