Crystal Oscillator Startup Using Frequency-Swept Drive
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Solution Overview
Problem
High-Q factor oscillators in micro-power wireless systems take significant time to startup, which exceeds the duration of data packets and increases power consumption due to their duty-cycled operation.
Innovation Solution
A circuit and method that utilize a driving oscillator to generate a startup signal with varying frequencies encompassing the operating frequency of a crystal oscillator, facilitated by a duty cycle adjuster and controller, to rapidly activate the crystal oscillator, reducing startup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a high-Q factor oscillator is used to generate reference clock, then oscillation stability is improved, but startup time increases significantly
Solution Approach 1:
The circuit applies a preliminary startup signal to the crystal oscillator before the main oscillation begins. This startup signal is generated by an oscillator circuit and applied through a coupling capacitor to the crystal oscillator input, preparing the crystal to oscillate more quickly when power is applied.
Solution Approach 2:
The patent introduces an intermediary startup signal circuit that mediates between the power supply and the crystal oscillator. This intermediary circuit generates a temporary startup signal that assists the crystal oscillator during the initial startup phase, then automatically disconnects once oscillation begins.
2Use of energy by moving object
If the system operates in duty-cycled mode to save power, then power consumption is reduced, but the oscillator startup time exceeds data packet duration
Solution Approach 1:
The startup signal circuit is activated in advance with the power supply signal and automatically shuts off after a predetermined time period or when oscillation is detected. This preliminary action enables the crystal oscillator to start up quickly during duty-cycled operation, ensuring the oscillator is ready before data packets are transmitted.
Solution Approach 2:
The circuit dynamically adjusts its behavior based on the operational state. The startup signal is applied only during the initial startup phase and automatically disconnected once the crystal oscillator begins oscillating, allowing the system to maintain low power consumption during duty-cycled operation while ensuring quick startup when needed.
3Stability of the object's composition
If the startup signal frequency matches the operating frequency, then oscillation stability is improved, but startup reliability decreases due to frequency variations
Solution Approach 1:
The startup signal circuit uses different frequency parameters than the final operating frequency. The oscillator circuit generating the startup signal can operate at a frequency that accounts for crystal variations and tolerances, ensuring reliable startup across different operating conditions while the crystal oscillator settles to its precise operating frequency once started.
Data Source
AI summary
A circuit includes a crystal oscillator to generate an output frequency for a circuit. A driving oscillator generates a startup signal having a driving frequency that is provided to activate the crystal oscillator. The driving frequency of the startup signal is varied over a range of frequencies that encompass the operating frequency of the crystal oscillator to facilitate startup of the crystal oscillator.