Crystal Oscillator Buffer Gain Switching for Noise-Stable Clocks
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Solution Overview
Problem
Conventional oscillators using high-gain inverters can amplify noise from poor-quality crystals, leading to instability in clock signals and frequencies due to full swing waveforms, which are prone to loading noises from different frequency bands.
Innovation Solution
A driving circuit with a buffer unit and control unit is coupled in parallel to the crystal, where the control unit detects the voltage level of the clock or oscillation signal to adjust the gain of the buffer, reducing amplification after stable oscillation is achieved to avoid excessive noise amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inverter with relatively great amplification is applied to actuate oscillation starting, then the oscillation can be started reliably even with poor quality crystals, but the full swing waveform generated can be loaded with noises of different frequency bands, leading to instability of the clock signal waveform and frequency
Solution Approach 1:
The patent applies a dynamic gain control mechanism where the buffer's amplification factor is adjusted based on the oscillation state. During startup, high gain is applied to ensure reliable oscillation starting. Once oscillation is established, the gain is reduced to prevent noise amplification. This dynamic adjustment resolves the contradiction between needing high gain for reliable startup and low gain for stable operation.
Solution Approach 2:
The control unit periodically monitors the oscillation signal and adjusts the buffer gain in periodic phases: initially applying high gain for startup, then switching to low gain for stable operation. This periodic monitoring and adjustment mechanism ensures both reliable oscillation starting and subsequent waveform stability.
2Adaptability or versatility
If an inverter with relatively great amplification is used to ensure oscillation starts, then poor quality crystals can be accommodated, but the amplification also amplifies noise generated by the crystal, influencing the waveform and frequency of the clock signal
Solution Approach 1:
The system dynamically adjusts the buffer gain based on oscillation detection. During the startup phase, high gain is maintained to accommodate poor quality crystals and ensure oscillation starts. Once oscillation is detected and stabilized, the gain is automatically reduced to minimize noise amplification, thereby preserving frequency precision while maintaining adaptability to different crystal qualities.
Solution Approach 2:
The control unit implements a feedback mechanism by continuously monitoring the oscillation signal characteristics. Based on this feedback, it determines when oscillation has started and adjusts the buffer gain accordingly. This feedback-controlled gain adjustment allows the system to adapt to various crystal qualities while maintaining precise frequency output once oscillation is established.
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 stabilizes the frequency of the clock signal by preventing noise from different frequency bands from being loaded into it, thereby improving the waveform and frequency stability.
Implementation Method 1
Since a mechanical-electrical resonance of the crystal 101 is quite stable, the oscillator 100 can output a relatively stable clock signal based on the above characteristic of the crystal 101.
Implementation Method 2
The buffer unit is coupled in parallel to the crystal, and used to amplify an oscillation signal outputted from the crystal to generate the clock signal.
Data Source
AI summary
An oscillator, a driving circuit and an oscillation method are provided. The driving circuit and a crystal are coupled in parallel to generate a clock signal. The driving circuit includes a buffer unit and a control unit. The buffer unit is coupled in parallel to the crystal, and used to amplify an oscillation signal outputted from the crystal to generate the clock signal. The control unit is coupled to the buffer unit, and used to generate a control signal to the buffer unit. The control unit determines a voltage level of the control signal by detecting whether the clock signal or the oscillation signal satisfies an oscillation condition of the crystal, so as to control a gain value of the buffer unit. Therefore, noise of different frequency bands loaded into the clock signal can be avoided.