Crystal Oscillation Circuit With Multi-Reference Varactors

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Solution Overview

Problem

In integrated circuit oscillation circuits, the limited variable capacitance of available components restricts the frequency variable width and linearity, leading to increased circuit scale and power consumption, especially when multiple level shift circuits are required for temperature compensation.

Innovation Solution

The oscillation circuit employs a set of variable capacitive elements with a common control voltage and different reference voltages applied to each element, eliminating the need for level shift circuits by using MOS variable capacitive elements and adjusting reference voltages to expand capacitance variability while maintaining linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single control voltage is applied to multiple variable capacitive elements with level shift circuits to expand frequency variable width, then the frequency variable width is improved, but the circuit scale and power consumption increase due to requiring multiple level shift circuits

Engineering Contradiction:

Improvefrequency variable widthVSAvoidcircuit scale

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies different reference voltages to multiple variable capacitive elements while using a common control voltage. This parameter change approach allows each capacitive element to operate in different voltage ranges, expanding the overall frequency variable width without requiring additional level shift circuits for each element.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The common control voltage serves all variable capacitive elements simultaneously, making it a universal control signal. This eliminates the need for separate level shift circuits for each element, reducing circuit scale while maintaining the ability to independently adjust each element's capacitance through its specific reference voltage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If multiple level shift circuits are used to apply different control voltages to variable capacitive elements for temperature compensation, then the compensation precision is improved, but the power consumption increases

Engineering Contradiction:

Improvecompensation precisionVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Different reference voltages are assigned to different variable capacitive elements, creating parameter diversity that enables precise temperature compensation for each element. This approach achieves high compensation precision without the power consumption overhead of multiple level shift circuits, as the voltage differentiation is achieved through reference voltage selection rather than active circuitry.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If integrated circuit implementation is used to reduce oscillator size, then the size is reduced, but the variable capacitance range is limited compared to discrete oscillators

Engineering Contradiction:

Improveoscillator sizeVSAvoidvariable capacitance range

Core Design Contradiction:

Volume of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent utilizes different reference voltage parameters for each variable capacitive element in the integrated circuit. This allows the integrated circuit to achieve a variable capacitance range comparable to discrete oscillators, as each element can be optimized for its specific operating range through parameter selection rather than requiring dedicated hardware for each element.

Inventive Principle:

Principle #35Parameter changes

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 configuration allows for expanded frequency variable width with maintained linearity, reducing circuit scale and power consumption without the need for additional level shift circuits, enhancing the performance and efficiency of integrated circuit oscillation circuits.

Implementation Method 1

the capacitance values of which are controlled with potential differences between reference voltages and a variable control voltage

Methodology Applied

Scientific EffectCapacitance variation with voltage: Capacitance

Implementation Method 2

connected to a resonator element and oscillates the resonator element to output an oscillation signal

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS9106237B2Oscillation circuit, electronic apparatus, and moving object

Publication Date: 2015.08.11 SEIKO EPSON CORP

AI summary

An oscillation circuit is connected to a resonator element (crystal resonator) and oscillates a resonator element to output an oscillation signal. The oscillation circuit includes an amplification element (inverter), and a set of variable capacitive elements having at least two variable capacitive elements, which are connected to an oscillation loop from an output to an input of the amplification element and the capacitance values thereof are controlled with potential differences between reference voltages and a variable control voltage. In each variable capacitive element of a set of variable capacitive elements, the common control voltage is applied to one terminal, and the reference voltage which differs between the variable capacitive elements is input to the other terminal.