Crystal Oscillator Startup Using Continuous Clock Injection
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Solution Overview
Problem
Crystal oscillators (XOs) in communication devices face a bottleneck in startup time, which is power-consuming and hinders efficient data transmission, especially when transitioning from sleep to wake modes, and existing methods to reduce startup time either increase power consumption or introduce inefficiencies.
Innovation Solution
The method involves using an external oscillator to inject energy into the XO core circuit with an injection switch always on during startup, and adjusting the injection frequency to match the intrinsic frequency of the XO, ensuring efficient clock injection by maintaining the relative phase within a specific interval, thereby reducing overall startup time without significant power increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the startup time of the XO is reduced by controlling negative resistance within the XO, then the startup speed is improved, but the power consumption increases
Solution Approach 1:
An external oscillator is introduced as an intermediary device to inject energy into the XO core circuit during startup. This external oscillator acts as a mediator that provides the necessary energy impulse to accelerate startup without requiring the XO's internal negative resistance control circuitry to consume additional power, thus resolving the contradiction between startup speed and power consumption.
Solution Approach 2:
Energy is injected into the XO core circuit before the XO's internal oscillation fully establishes. By applying preliminary energy injection from the external oscillator during the startup phase, the system achieves faster startup without sustained additional power consumption, as the external oscillator only operates during the transient startup period.
2Productivity
If the injection switch is turned on and off iteratively to optimize clock injection efficiency, then the injection efficiency is improved, but the control complexity increases
Solution Approach 1:
A feedback mechanism monitors the energy injection process and provides information about the XO's oscillation state. This feedback enables the control circuit to adjust the injection switch timing and duration optimally, achieving high clock injection efficiency without requiring complex iterative switching sequences. The feedback loop automatically adapts to maintain optimal injection conditions.
Solution Approach 2:
The injection switch control is made dynamic rather than static, allowing the switch to be adjusted in real-time based on the XO's startup progress. This dynamic control enables optimization of clock injection efficiency by adapting the injection parameters during startup, while keeping the control logic manageable through systematic adjustment rather than complex iterative sequences.
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
This approach significantly reduces the XO's startup time while maintaining efficiency, optimizing performance without introducing side effects, and ensuring continuous energy growth of the intrinsic oscillation signal.
Implementation Method 1
an external oscillator is configured to generate an injected signal, wherein the injected signal is transformed and injected into an XO core circuit through an injection switch
Implementation Method 2
the XO may enter a wakeup mode for startup of oscillation
Data Source
Figure 1
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Figure 4
AI summary
A method for startup of a crystal oscillator (20), XO, with aid of external clock injection, associated XO core (100) and a monitoring circuit (300) therein are provided. The XO includes an XO core circuit (100), an external oscillator (200), and an injection switch (INJEN), where a quality factor of the external oscillator (200) is lower than a quality factor of the XO core circuit (100). The method includes: utilizing the external oscillator to generate an injected signal; turning on the injection switch to make energy of the injected signal be injected into the XO core circuit, where an amplitude modulation, AM, signal is generated according to combination of the injected signal and an intrinsic oscillation signal from the XO core circuit; and controlling the external oscillator to selectively change an injection frequency of the injected signal according to the AM signal. More particularly, the injection switch is not turned off until the startup process is completed.