A METHOD TO PRE-CHARGE CRYSTAL OSCILLATORS FOR FAST START-UP

摘要

A method and apparatus for charging a crystal oscillator are provided. A voltage generating module outputs a ramp voltage signal to a ring oscillator. The ring oscillator generates and outputs a waveform based on the ramp voltage signal. The ramp voltage signal facilitates the ring oscillator to output the waveform at a frequency that varies with time, wherein the varying frequency is within a frequency range of the crystal oscillator. An inverter generates a digital input signal based on the waveform. The digital input signal is sent to an input of the crystal oscillator for charging the crystal oscillator. A feedback module outputs a feedback signal based on the digital input signal, wherein the feedback signal controls the voltage generating module to generate a fixed voltage signal that facilitates the ring oscillator to output the waveform at a frequency that is equal to a resonance frequency of the crystal oscillator.