The Design Of A Ring Oscillator With Digital Self-calibration

In communication,industrial control,instrumentation,medical electronics and many other fields,the oscillator plays a very important role.In the context of the increasing progress of integrated circuit technology and the continuous improvement of integration,the oscillator and other modules are integrated into the era of monolithic integration.The performance of on-chip CMOS oscillators is mainly affected by process variations,supply voltage fluctuations,and temperature changes,resulting in a certain deviation from the expected frequency of the actually produced oscillator.In order to compensate for the effects of process variations,supply voltage fluctuations,and temperature changes on the oscillator frequency,the common practice is designed a temperature or process compensation circuit for use in an oscillator to attenuate the temperature and influence the process on the performance of the oscillator.In view of the above situation and the relevant literature in recent years,a method of frequency calibration for an on-chip ring oscillator,which can be used by external reference clock,is designed in this paper.The principle of this method is as follows: by comparing the frequency of the ring oscillator and the external reference clock by the digital self-calibration algorithm,the control word is adjusted to change the working current of the ring oscillator,and then the frequency of the ring oscillator is calibrated to the expected range.This method can effectively compensate the effect of process bias on oscillator frequency.The main work of this paper is as follows:First,a frequency-adjustable ring oscillator is designed.By changing its working current,the frequency can be adjusted.At the same time,working current can reduce the amplitude of its oscillation and reduce its power consumption.After the level conversion circuit and the plastic circuit,the output can be used directly for the subsequent circuit.Secondly,the voltage-current conversion circuit and bandgap reference are designed.By controlling the size of the binary weight switch resistor in the voltage-current conversion circuit,the working current of the ring oscillator can be changed.The bandgap reference source provides a reference voltage with smaller drift coefficient for voltage to current conversion circuit.Then,the digital self-calibration algorithm is designed,through the digital self-calibration algorithm can complete the frequency comparison,control word repair,accurate comparison and determine the calibration and other operations,and then the control word of the EEPROM reading and writing design.Finally,the layout of the analog and digital part is designed.Based on the TSMC 0.35?m technology,the design and Simulation of the cadence platform are carried out in this paper.The simulation results are consistent with the expected results.It has a certain reference value for the research and design of on chip CMOS oscillator.