A method for fast start-up of crystal oscillator

Abstract

The present invention discloses a crystal oscillator rapid oscillation-starting method. The method comprises the following steps: (1) a quartz crystal XTAL and a load capacitor C1 being parallel in the quartz crystal XTAL form a crystal resonance circuit; (2) a differential amplifier OTA, a controlled current source g1 and a crystal resonance circuit form a positive feedback dominant resonance loop (Loop 1); (3) the differential amplifier OTA, a controlled current source g2 and a capacitor C2 form a capacitance compensation loop (Loop 2); (4) the compensation loop generates equivalent negative capacitance to the dominant resonance loop in the oscillation process to reduce or offset the parallel equivalent capacitance at the two ends of the crystal; and (5) the positive feedback gain is increased without the restriction of the equivalent parallel capacitance of the crystal, and the circuit oscillation starting is accelerated. The circuit and the crystal oscillator rapid oscillation-starting method provided by the invention are able to overcome the problem that the positive feedback gain of a routine crystal oscillation circuit is not helpful for acceleration of the oscillation starting after being increased to a certain extent, and are able to effectively accelerate the oscillation starting of the crystal oscillator through compensation and reduction of the crystal parallel equivalent capacitance and the chip packaging base pin parasitic capacitance.

Description

technical field [0001] The invention relates to an oscillator circuit in an electronic circuit, in particular to a method for fast start-up of a crystal oscillator. Background technique [0002] Quartz crystal oscillators are widely used in modern electronic products, providing clocks for digital circuits and reference frequencies for analog circuits. An oscillator circuit is usually composed of electronic devices, and then a crystal oscillator is formed with an external quartz crystal. Among them, because the crystal has a very high quality factor (Q value), it drives the oscillator circuit to work in a very narrow frequency range, that is, the circuit reaches a resonance state, thus providing a relatively accurate and stable clock and frequency signal. [0003] The start-up time of the existing crystal oscillator is usually at the millisecond level. In a system that requires frequent start-stop and only needs to work for a short time, the time occupied by the crystal osci...

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Problems solved by technology

[0006] That is to say, the parallel equivalent capacitance of the crystal itself, as well as the equivalent capacitance inside the oscillation circuit and on the pin package, will limit the absolute value of the maximum negative resistance formed by positive feedback, so that the positive feedback gain will continue to increase after a certain critical point On the contrary, it will reduce the absolute value of the negative resistance, thus limiting the effect of increasing the positive feedback gain on accelerating vibration

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