Design Of Low Power Crystal Oscillator For Real Time Clock

In order to save energy,the typical mode of operation of the wireless sensor node is usually composed of a short activation operation and a long idle state.Real-time clock is the only work in the idle state of the circuit,which is used to wake up the system,the system scheduling and synchronize different sensor nodes.Its power consumption determines the total power consumption of the system.Crystal oscillator is an important source of real-time clock power consumption,the design of low-power crystal oscillator to reduce the wireless sensor node power is very important.In this thsis,a low power crystal oscillator is designed by using pulse-driven and multi-voltage domain method.The main work includes:1)Establishing a switch pulse crystal model to verify the feasibility of the pulse drive method;2)In order to reduce the energy consumed by the crystal itself,this thsis decomposes the traditional inverter structure into the preamplifier stage and the rear driving stage,and makes the two work in the high voltage domain and the low voltage domain respectively.The preamplifier stage is composed of FE,DLL,pulse generator and level shifter,which converts the crystal input signal into a high voltage pulse wave,and then drives two NMOS tubes and PMOS tubes.3)In order to reduce loss energy of the drive,this thsis uses a pulsed charging method.The circuit periodically generates a charge and discharge pulse through the DLL in order to instantaneously inject the energy into the circuit and briefly turn on the drive,thereby suppressing the quiescent current in the drive.4)In order to reduce the power consumption of FE and DLL,this thsis uses the frequency divider to generate periodic enable signal to control FE and DLL work cyclely.Based on the SMIC40nm three-well process,the design of the low-power crystal oscillator is completed.The layout area is 0.115mm2.The operating voltage range is 0.94V-1.2V,the working temperature range is-20-+85 ?;Between-20 and +85 ?,the frequency deviation is-185ppm to-8ppm.