Crystal Oscillator Feedback Injection for Faster Start-Up
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Solution Overview
Problem
Crystal oscillators with high quality factors take a long time to start up, which affects power consumption in small wireless devices, and existing frequency injection methods are not robust against environmental changes like temperature variations.
Innovation Solution
A crystal oscillator circuit with an injection frequency generating circuit that amplifies and injects a signal back into the crystal oscillator, reducing start-up time and being insensitive to environmental changes by using a two-stage operational amplifier and dynamically adjustable load capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If frequency injection is used to reduce start-up time, then start-up time is reduced, but the injection frequency must be very close to the crystal oscillator frequency which drifts with environmental changes
Solution Approach 1:
The injection frequency generating circuit senses the crystal oscillator's own signal and uses it as the injection source. The circuit amplifies the sensed signal and feeds it back to the crystal oscillator, making the system self-regulating and automatically adapting to frequency drift without external calibration
Solution Approach 2:
The circuit senses the output signal from the crystal oscillator and feeds it back through an amplifier to the input of the crystal oscillator. This feedback mechanism ensures the injection frequency automatically tracks the crystal oscillator frequency despite environmental variations
2Loss of time
If a driving oscillator with variable frequency is used to activate the crystal oscillator, then start-up is facilitated, but the driving oscillator needs to be calibrated and adapted to the crystal oscillator
Solution Approach 1:
Instead of using an independent driving oscillator that requires calibration, the circuit uses the crystal oscillator's own signal as the injection source. This eliminates the need for separate calibration procedures and reduces device complexity while maintaining fast start-up capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly reduces the start-up time of the crystal oscillator, making it more robust against environmental variations and minimizing power consumption, especially in wireless sensor nodes.
Implementation Method 1
an injection frequency generating circuit, the injection frequency generating circuit being configured to sense a signal of the crystal oscillator and amplify the sensed signal
Implementation Method 2
Crystal oscillators are widely used as a reference clock or a real time counter in various applications
Implementation Method 3
A crystal oscillator having a high quality (Q) factor
Data Source
AI summary
A crystal oscillator circuit comprises: a crystal oscillator; and an injection frequency generating circuit, the injection frequency generating circuit being configured to sense a signal of the crystal oscillator and amplify the sensed signal, the injection frequency generating circuit being further configured to inject the amplified signal to the crystal oscillator; wherein the crystal oscillator circuit is configured such that the crystal oscillator receives the amplified signal during an initial start-up period of the crystal oscillator and stops receiving the amplified signal at an end of the initial start-up period.