The Design And Research Of Integrated OCXO

Quartz crystal oscillator in the controller, TV, computer, all kinds of instruments inthe oscillation circuit has a wide range of applications. In the communication system it isused in frequency generator to generate the clock signal for data processing devices. Withthe development of modern electronics, aerospace and other measurement and controlsystems, the demand for system frequency source is increasingly higher, not only highfrequency stability for extremely long time, but also the excellent short-term frequencystability and phase noise of the frequency source is in desperate need is necessary. Due tothe character of higher frequency stability, oven controlled crystal oscillator are widelyused in national defense, aerospace, satellite navigation, mobile communication basestation, frequency counter, and other instruments.The core content of this paper is to design a specific chip of temperature crystaloscillator, reducing its bulk as much as possible. PTAT technology is adopted to test thetemperature of constant temperature trough accurately, and the tested temperature andconstant temperature are compared. When the temperature is lower than the constanttemperature point, hip controlled heating resistance provides large heating power. Whenthe temperature is higher than the constant temperature point, the heating power is smaller.PID control and PWM modulation technology are used to achieve temperature controlsteadily. The chip design includes each module circuit designs and simulation, the wholecircuit designs and simulation, and layout drawing. SMIC0.18um CMOS technology isadopted for the designing of every modules of oven controlled crystal oscillator, includingbandgap reference voltage and temperature sensor module, error amplifier, PID controlmodule, PWM output driver and circuit crystal oscillator module. Simulation analysis ofthe circuit is conducted by the use of Spectre environment, adjusting the circuit forperformance optimization. According to some basic layout design rules of the circuit chip,Virtuoso software is applied in drawing each module circuit’s layout the overall layout.Through circuit simulation, the temperature sensitivity of the temperature detection is12.925mV/℃. When it control the temperature， heating power and steady power can reach4W and1.65W respectively. With1℃change of temperature near the constanttemperature, the variation of power is0.034W. The results show that the temperaturecontrol is basically realized in the chip.