Crystal Oscillator Noise Injection for Faster Start-Up
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Solution Overview
Problem
Existing crystal oscillator circuits in semiconductor devices have long start-up times, and previous methods to reduce this time either have limited effectiveness or require complex circuitry that is not suitable for mass production.
Innovation Solution
A semiconductor device with a crystal oscillator circuit that includes a first and second noise application circuit, which selectively apply initial noises of opposite phases to a crystal resonator, using capacitance coupling circuits and amplifier circuits to shorten the start-up time while reducing the overall circuit scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional crystal oscillator circuit is used, then frequency accuracy is maintained, but start-up time becomes long
Solution Approach 1:
The patent applies preliminary action by introducing initial noise signals to the crystal resonator before the oscillator naturally starts up. The noise application circuits generate and apply noise signals at the resonant frequency of the crystal resonator during the start-up phase, which accelerates the oscillation build-up process. Once the oscillator reaches a stable state, the noise application is stopped, thus achieving fast start-up without affecting the frequency accuracy during normal operation.
2Loss of time
If Chirp Injection method is used, then start-up time is reduced, but the effect is limited due to single frequency crossing
Solution Approach 1:
The patent segments the noise application process into two distinct stages: a first noise application circuit that applies noise during the initial start-up phase, and a second noise application circuit that applies noise after the oscillator has started but before stable operation. This segmentation allows each circuit to be optimized for its specific phase, with the first circuit providing initial excitation and the second circuit ensuring rapid convergence to the resonant frequency, thereby overcoming the limitation of single-stage methods.
3Loss of time
If two-stage noise application with accurate frequency matching is used, then start-up time is greatly reduced, but circuit scale increases due to PLL and trimmed oscillator requirements
Solution Approach 1:
The patent employs simple noise application circuits that generate noise signals without requiring complex frequency control mechanisms like PLLs or precisely trimmed oscillators. The noise circuits use basic components such as resistors, capacitors, and switches to generate broadband noise that is applied to the crystal resonator. These noise application circuits are temporary and are disabled once the oscillator starts up, replacing the need for permanent, complex frequency control circuitry.
Solution Approach 2:
The patent changes the operational parameters of the noise application circuits based on the oscillation state. The first noise application circuit operates with higher noise amplitude during the initial start-up phase, while the second noise application circuit operates with lower noise amplitude after oscillation begins. The circuits are dynamically enabled and disabled based on oscillation detection, allowing effective start-up acceleration without requiring complex frequency matching circuitry throughout the entire operation.
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 circuit, from 0.98 ms to 0.14 ms, while maintaining frequency accuracy and allowing for smaller circuit scale, making it suitable for mass-produced semiconductor devices with reduced power consumption.
Implementation Method 1
the first capacitance coupling circuit is provided so as to take an alternating current component of a signal at the first external terminal by separating a direct current voltage at the first external terminal from a direct current voltage at an input terminal of the amplifier circuit
Implementation Method 2
the amplifier circuit is provided so as to amplify the alternating current component taken by the first capacitance coupling circuit, convert it into a clock signal, and drive the first external terminal with the converted clock signal
Implementation Method 3
a crystal oscillator circuit that includes a first and second noise application circuit, which selectively apply initial noises of opposite phases to a crystal resonator
Data Source
AI summary
A semiconductor device includes a crystal oscillator circuit, a first noise application circuit, and a second noise application circuit. The first noise application circuit is connected to the crystal oscillator circuit and is configured to drive a crystal resonator by selectively applying initial noises of opposite phases to a first external terminal and a second external terminal. The second noise application circuit applies a second noise to the first external terminal by amplifying a signal at the first external terminal and returning the amplified signal to the first external terminal, thereby driving an oscillation amplifier and a crystal resonator of the crystal oscillator circuit and shortening a start-up time of the crystal oscillator circuit.