Push-Start Crystal Oscillator Using PLL Feedback for Fast Wake-Up
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Solution Overview
Problem
Existing start-up methods for crystal oscillators are sensitive to environmental factors and require time-consuming calibration, which increases hardware costs and is not practical for frequent wake-up modes.
Innovation Solution
A push-start crystal oscillator system utilizing an inverting amplifier and a push-start logic control circuit, coupled with a phase locked loop (PLL), generates a first and second XO signal, where the PLL calibrates the frequency during a settle phase and increases the amplitude of the first XO signal during a push phase, reducing the need for additional calibration circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time-consuming calibration is performed to ensure efficient start-up, then start-up reliability is improved, but calibration time increases and cannot be performed frequently
Solution Approach 1:
The patent performs calibration during a settle phase that occurs before the actual start-up push phase. By preliminarily calibrating the feedback clock frequency to match the crystal oscillator frequency during the settle phase, the system ensures accurate frequency alignment is established in advance, making the subsequent start-up process reliable and fast without requiring additional calibration time during wake-up.
Solution Approach 2:
The patent implements periodic calibration by alternating between settle phases and push phases. The settle phase performs frequency calibration, while the push phase executes the actual start-up. This periodic alternation allows the system to maintain calibrated frequency alignment across multiple start-up cycles, enabling frequent wake-ups with consistent reliability.
2Productivity
If additional calibration circuits are added to reduce calibration time, then calibration speed is improved, but hardware cost increases
Solution Approach 1:
The patent makes the feedback clock from the PLL serve multiple functions: it is used both for frequency calibration during the settle phase and for pushing the crystal oscillator during the push phase. This multi-functional use of existing PLL output eliminates the need for separate calibration circuits, achieving fast calibration without increasing hardware complexity or cost.
Solution Approach 2:
The system uses its own feedback clock signal to perform both calibration and start-up functions. The PLL's feedback clock automatically serves the dual purpose of calibrating the frequency alignment and providing the push signal, making the system self-sufficient without requiring external or additional dedicated calibration hardware.
3Device complexity
If conventional start-up methods are used, then hardware complexity is reduced, but start-up performance becomes sensitive to environmental factors
Solution Approach 1:
The patent employs feedback by continuously monitoring the crystal oscillator frequency and using the PLL to adjust and match the feedback clock frequency to the crystal frequency during the settle phase. This feedback mechanism compensates for environmental variations such as temperature changes, ensuring the start-up performance remains stable and reliable without requiring complex additional hardware.
Data Source
AI summary
A push-start crystal oscillator (XO), an associated electronic device and a push-start method for performing a start-up procedure of an XO are provided. The push-start XO includes an inverting amplifier and a push-start logic control circuit, wherein the inverting amplifier is coupled to a crystal load. The inverting amplifier generates a first XO signal and a second XO signal. The push-start logic control circuit receives a feedback clock from a phase locked loop (PLL), and generates a phase control clock according to the feedback clock, wherein a push phase and a settle phase are specified by the phase control clock. During the settle phase, the PLL calibrates a frequency of the feedback clock according to the second XO signal. During the push phase, the feedback clock is transmitted to the inverting amplifier in order to increase the amplitude of the first XO signal.