Crystal oscillator and startup method for a crystal oscillator

Abstract

A crystal oscillator and a startup method for initiating operation of a crystal oscillator, the crystal oscillator includes an oscillator structure including a crystal resonator and an electronic oscillator circuit connected to the crystal resonator, the oscillator structure having a first terminal and a second terminal, a startup controller operable to initiate an oscillation in the oscillator structure by exciting the oscillator structure with a sequence of excitation signals derivable from a clock signal and when triggered by a timing signal, the sequence of excitation signals includes at least a first excitation signal and a second excitation signal, a comparator including a first and a second input terminal and an output terminal, the first input terminal being connected to the first terminal and wherein the second input terminal is connected to the second terminal.

Description

FIELD OF THE INVENTION[0001]The present disclosure relates to a crystal oscillator and to a portable electronic device comprising such a crystal oscillator. In another aspect the disclosure relates to a method of initiating operation of a crystal oscillator.BACKGROUND OF THE INVENTION[0002]Crystal oscillators are widely known in the prior art. A crystal oscillator is an electronic oscillating circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electric signal with a precise frequency. This frequency is often used to keep track of time, as in quartz-controlled wristwatches in order to provide a stable clock signal for digital integrated circuits and / or to stabilize frequencies for radio transmitters and receivers.[0003]Conventional crystal oscillators of the so-called Pierce- or Colpitts-type design are typically provided with two capacitors that are usually excited by a controller to provide a rather fast startup of the oscillator...

AI Technical Summary

Benefits of technology

[0012]The crystal oscillator further comprises a phase shifting unit coupled to the digital storage and coupled to the output terminal of the comparator. The phase shifting unit is operable to generate or to modify the timing signal on the basis of the comparative signal and on the basis of the digital data provided by the digital storage. In this way the dispersion of the comparator and the impact of the dispersion on the correct determination of the phase of the oscillator structure can be effectively compensated.

[0039]Accordingly and when in the operation mode the digital data is retrieved from the digital storage and the timing signal is generated or modified on the basis of the comparative signal as provided by the comparator of the crystal oscillator and on the basis of the retrieved digital data. In this way and when in the operation mode the impact of comparator dispersion can be effectively compensated for.

Problems solved by technology

Insofar, the quality or precision of the phase information derived from the comparator may be somewhat affected.

It may be even false.

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