Design And Implementation Of High Accuracy And Low Power Wakeup Oscillator

Wireless sensor network is a typical representative of Internet of Things.Heavily duty-cycled mode is adopted for sake of power saving,and the wakeup clock's power consumption in sleep mode is the main part of the total power consumption.In addition,the accuracy of the clock is very important for the communication between sensor nodes.Although the commonly used 32 kHz real-time clock has high accuracy,its power consumption is still high,and quartz crystal is not conducive to chip integration.Therefore,a wakeup clock circuit based on self-biased voltage-controlled oscillator(VCO)is proposed.The basic principle and implementation method of wake-up clock circuit is systematically elaborated.In view of the clock generation circuit,the structure of several types of oscillator is introduced in detail.A differential input delay unit based on transistor leakage is adopted to form a ring oscillator,in order to adapt to low frequency and low voltage operation.For the bias voltage generation circuit,a series structure of switched resistor and capacitor is adopted.Switched resistor plays the role of current reference circuit,which reduces the overall circuit power consumption.The resistor with different temperature coefficients is used to compensate the temperature drift to make the output frequency of the circuit more accurate.In order to improve the frequency stability,trimming switch is added to the design,which can not only calibrate the output frequency under different process deviations,but also fine-tune the frequency changes caused by temperature changes.The design is implemented based on GF130nm process whose area is 0.496mm~2.The post-simulation results show that the frequency stability of the oscillator is 45ppm/℃when the temperature ranges from-30℃to 90℃,and 1.1%/V when the supply voltage climb from 0.7V to 1.3V.The output frequency of the oscillator is 1kHz and the power consumption is 3.71 nW at TT-1V.Compared with the existing research,the clock accuracy is improved by 8 times to 35times,and the power consumption is reduced by 36%compared with the current design with the highest accuracy.