Study And Design Of CMOS RC Relaxation Oscillator

The RC relaxation oscillators,as the on-chip clock source,are widely used in circuits in the Internet of Things equipment and other fields.There are some functions of providing accurate timing,waking up the system and network synchronization occupied by Io T(Internet of Thing)devices.With the development of Io T technology,considering of long endurance and high-precision clock source signals in many distributed Io T devices,the RC relaxation oscillators are required to have better performance of power consumption and temperature drift.In this thesis,a low-temperature drift RC relaxation oscillator and a low-power RC relaxation oscillator are designed for the application of Io T devices.Aiming at the problems of temperature drift caused by comparator delay in a typical voltage mode RC relaxation oscillators,a low-temperature drift RC relaxation oscillator without a comparator was designed to fundamentally eliminate the influence of non-ideal factors such as comparator delay and offset voltage.The threshold detection circuit was used to replace the comparator,the first-order RC circuit was used to complete the charge and discharge of the capacitor,and the latch circuit was used to temporarily maintain the original level state of the output waveform before the switching threshold voltage arrives.Derived by the formula,it is shown that the temperature dependence of the RC oscillator without comparator in this paper mainly depends on the switching threshold coefficient of the latch,so that the oscillator has high temperature stabilityAiming at the problems of large power consumption in typical current mode RC relaxation oscillator circuit,a low-power current-mode RC relaxation oscillator was designed.the reference voltage and self-bias current generating circuit were combined,the structure was simplified and enough small supply voltage and bias current were used in RC relaxation oscillation,and all of which were used to reduce power dissipation.The cascade common gate and common source structure,the inverter chain and the clock voltage booster were utilized to form a buffer structure,which was used to reduce the power comsumption and influence of temperature to the delay and oscillation frequency.The low-temperature drift RC relaxation oscillator and the low-power RC relaxation oscillator are designed using the SMIC 130 nm CMOS process,and the pre-simulation and postsimulation are performed based on the Cadence Virtuoso platform.In the layout design,methods such as adding guard-ring to isolate each module are used to optimize The presimulation result shows that the designed low temperature drift RC relaxation oscillator has a temperature drift coefficient of 64.8 ppm/? within the range of-20??80?,under a 2.0V power supply voltage and 27? temperature,which is 84.6 ppm/? lower than that of a typical voltage mode RC relaxation oscillator,and which shows that the temperature drift performance is significantly improved.The designed low-power current-mode RC relaxation oscillator has an oscillation frequency of 1.0 k Hz at a supply voltage of 0.6V and a temperature of 27?,and the power consumption of the circuit is 1.732 nW,which is lower than the typical current-mode RC relaxation oscillator 71.47 nW,which shows a significant improvement in power consumption performance.