Temperature compensation circuit for crystal oscillator

Abstract

The invention belongs to the field of integrated circuits, and specifically relates to a temperature compensation circuit for a crystal oscillator. The temperature compensation circuit generates reference voltage Vref of a third power function for temperature, and controls the magnitude, monomial coefficient, quadratic coefficient and ternary coefficient of the output reference voltage under the actions of control signals Cont-Rm1, Cont-Rm2, Cont-Rm3 and Cont-NL, so as to change the temperature coefficient and the zero temperature coefficient point of the reference voltage according to the temperature-frequency characteristics of different crystals. The reference voltage controls the capacitance of a variable capacitance diode, so as to accurately compensate the offset of the oscillation frequency of the crystal oscillator due to temperature changes and improve the temperature stability of the frequency. The temperature compensation circuit generates the reference voltage with different temperature coefficients and zero temperature coefficient points for crystals with different temperature characteristics, is high in flexibility, high in compensation precision, simple in structure and low in cost, and facilities miniaturization and integration.

Description

technical field [0001] The invention belongs to the field of integrated circuits, and relates to a temperature compensation circuit of a crystal oscillator, in particular to a reference voltage generation circuit with a cubic function to temperature. Background technique [0002] As a stable frequency source, crystal oscillators are widely used in portable electronic equipment and wireless communication technology, and the stability of their frequency to temperature changes is one of the important indicators to measure the performance of crystal oscillators. The temperature compensated crystal oscillator reduces the offset of the crystal oscillator output frequency due to temperature changes through a temperature compensation network, thereby improving frequency stability. [0003] For the AT-cut quartz resonator commonly used in crystal oscillators, the relationship between its resonant frequency and temperature is described by a cubic curve, specifically: [0004] f(T)=f ...

AI Technical Summary

Problems solved by technology

[0017] Aiming at the shortcomings of the existing crystal oscillator temperature compensation network, such as high cost, complex circuit structure, and difficulty in integration and miniaturization, the present invention provides a temperature compensation circuit for crystal oscillators. The temperature compensation circuit is based on the temperature of different crystals. Characteristics, generating a reference voltage with adjustable size and temperature coefficient that is a cubic function of temperature. The reference voltage changes the load capacitance of the crystal by controlling the capacitance of the varactor diode, thereby compensating the offset of the crystal oscillation frequency due to temperature changes. Improve frequency stability

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