An Ultra-high Frequency Stability ATCXO Circuit Research And Design

From the time since it was recognized, it is possible to obtain an accurate measurement of time frequency source has been one of the objectives pursued. Quartz crystal oscillator has a high no-load quality factor(Q) and minimal access coefficient, so it has good frequency stability and precision of the clock signal as an important benchmark to use. Meanwhile, the rapid development of portable electronic products.The year 2013 global Mobile phone shipments reached 1.8 billion, a cell phone,at least there will be a quartz crystal, The huge demand in the crystal oscillator performance, small size, low under the multiple requirements power, high frequency degree, temperature characteristics inherent in the crystal. It becomes a factor restricting the application temperature range, and the application, resulting in a specific characteristic of the crystal temperature compensation chip. Now there are digital temperature compensated crystal oscillator, the Microcomputer Compensated crystal oscillator, ATCXO compensation in several different ways of crystal oscillator. TCXO in the simulation of chip area, cost, compensation, precision, have good balance, obtained the widespread application. The research focus to obtain high frequency stability is easy to simulate temperature integration to the compensated crystal oscillator.This paper presents an ultra-high frequency stability of analog temperature compensated crystal(ATCXO) oscillator circuit. The chip using advanced integrated circuit manufacturing technology. The analog compensation circuit and voltage-controlled crystal oscillator integrated in a single chip, making crystals and when using only a single chip with the use(which can be packaged in the same envelope), to provide high-precision frequency source over a wide temperature range. Firstly, studied the characteristics and equivalent circuits for quartz crystal, discusses ATCXO types and architecture, made crystal oscillator frequency elegant solution with temperature. Use the circuit to achieve a temperature probe, a five-th order function generator, a voltage controlled oscillator(VCXO) and other circuits, and through chip embedded EEPROM and ROM trimming the compensation characteristic can further improve the accuracy of their compensation. Where the bandgap reference circuit using cascode structure, it has high power supply rejection ratio. VCXO selects the Pearce capacitor of three terminal oscillator, and for its shortcomings were improved, the compensation capacitor using MOS capacitor to implement a low cost, then use HSPICE Fourier analysis of the CMOS capacitance characteristics under large signal, The five-th order function generator using CMOS technology, low cost, low power consumption, trimming circuit voltage by five square function of the temperature of the inflection point, five coefficients, four coefficients, three coefficient, a key factor, since the crystal oscillator frequency parameters such as memory adjustment. By adjusting the parameters, can be of different sizes crystal oscillator frequency compensation, to achieve a stable frequency output function quadrillion compensation herein. The Five-th order function compensation in this paper by using the ATCXO more accurate than using a cubic function, compensation had more high temperature frequency stability.Finally, based on the completion of circuit theory analysis and design of the sub-circuits,using the advanced 0.35 um analog chip production process, draw the layout and complete the flow sheet. Designed to meet the mobile communications, digital networks and a variety of portable electronic products and other needs. the chip supply voltage2.7~5.5V, frequency of 13 MHz, it is within-40 ~ 85 ℃(-20 ~ 70 ℃) range,with temperature frequency deviation of less than ± 1ppm(± 0.5ppm), used to make domestic chip monopoly status of foreign enterprises. The whole design process in the Linux system HSPICE simulation tool, Cadence integrated circuit design environment based on.