A Research And Design Of Temperature Compensated Crystal Oscillator

It has a higher and higher demands on the accuracy of the clock source in the Modernelectronics, communications equipment. In the various methods for clock source, Crystaloscillator is widely available for it has excellent stability and accuracy.However, the oscillationfrequency of the crystal oscillator is still subject to a number of factors (such as electromagneticinterference, mechanical vibration, humidity and temperature, etc.), especially the temperaturehas a great impact on it. In order to obtain a precise frequency source, it is necessary tocompensate the oscillator circuit in a certain range of the temperature.In this thesis, the temperature compensated crystal oscillator circuit research and design.This paper investigates the problems about the temperature compensated crystal oscillatormainly includes an adjustable frequency oscillator, the bandgap temperature measurement circuit,the analog-to-digital converter (AD), as well as the LDO. The thesis study the mathematicalmodel of the crystal first, and then analyse the principle of vibration of the quartz crystaloscillator and the compensation methods with the method of negative resistance, and design adigital capacitance array adjustable crystal oscillator circuit to make the oscillationfrequency controlled.The Bandgap temperature measurement circuit with a the LDO supplyand cascode structure achieved a high power supply rejection ratio and accuracy of thetemperature voltage. Analog-to-Digital Converter ADC uses a12-bit successive approximationcircuit has a simple structure and a Moderate accuracy. The LDO for temperature measurementcircuit is to provide a stable power supply to ensure the stability of the output signal, and the lowpower consumption of the entire system by working intermittently.With the development of the CMOS technology, the various circuits described above can beintegrated on a chip. In this thesis, based on the IC design tools Cadence software environment,and SMIC0.35um process, design the above circuit, and the simulation results verify thefeasibility of the design.