LC Oscillator Circuit for Temperature Compensation Under Parasitic Capacitance
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Solution Overview
Problem
Semiconductor integrated circuits with internal LC oscillators face challenges in maintaining stable oscillation frequency across varying temperatures due to parasitic capacitance and resistance, making temperature compensation complex and requiring larger circuit scales.
Innovation Solution
An oscillator design that includes an inductance element, capacitance element, and amplifier coupled in parallel, with a first resistance element having a larger resistance than the parasitic resistance of the inductance element, coupled in series with the capacitance element, to compensate for temperature variations and parasitic capacitance, ensuring stable oscillation frequency across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple temperature compensation method is used, then the circuit scale is reduced, but the oscillation frequency stability across temperature variations deteriorates
Solution Approach 1:
The patent applies parameter changes by utilizing the temperature coefficient of resistance of the first resistance element to counteract the temperature-dependent variations in the parasitic resistance of the inductance element. By carefully selecting the resistance value and temperature coefficient of the first resistance element, the combined temperature characteristics of the resistance elements compensate for frequency drift, achieving stable oscillation frequency without complex compensation circuits.
2Reliability
If the resistance value of the first resistance element is increased to compensate for parasitic capacitance, then the temperature compensation effectiveness improves, but the impact of resistance tolerance on frequency accuracy worsens
Solution Approach 1:
The patent optimizes the resistance value of the first resistance element to achieve a balance between temperature compensation effectiveness and frequency accuracy. The resistance value is specifically designed to be larger than the parasitic resistance to effectively counteract parasitic capacitance effects, while the temperature coefficient is selected to match the parasitic resistance characteristics, minimizing the impact of resistance tolerance on overall frequency accuracy.
Solution Approach 2:
The patent converts the harmful effect of resistance tolerance into a beneficial temperature compensation mechanism. By designing the first resistance element with a temperature coefficient that matches the parasitic resistance, the tolerance in resistance value becomes less critical because the temperature-dependent behavior provides the primary compensation effect, reducing the impact of manufacturing variations on frequency accuracy.
3Area of stationary object
If internal LC oscillator is used instead of external crystal oscillator, then the substrate size and cost are reduced, but the temperature compensation complexity increases
Solution Approach 1:
The patent merges the temperature compensation function directly into the oscillator circuit by integrating the first resistance element in series with the capacitance element. This unified approach eliminates the need for separate compensation circuits, maintaining compact substrate size while providing effective temperature compensation through the inherent temperature coefficient of the resistance element.
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 effectively compensates for temperature-dependent oscillation frequency variations, providing a stable and accurate clock signal for semiconductor integrated circuits, even with large parasitic capacitance, by using a resistance element with a matching temperature coefficient to the inductance element, thus minimizing frequency jitter.
Implementation Method 1
using a resistance element with a matching temperature coefficient to the inductance element
Implementation Method 2
amplifier that amplifies the resonance generated by the inductance element and capacitance element
Data Source
AI summary
An oscillator and a semiconductor integrated circuit device with an internal oscillator capable of compensating the temperature characteristics even when there is a large parasitic capacitance too large to ignore directly between the output terminals of the oscillator. In an oscillator containing an inductance element L, and a capacitive element C, and an amplifier each coupled in parallel across a first and second terminal, the amplifier amplifies the resonance generated by the inductance element and capacitive element and issues an output from the first terminal and the second terminal, and in which a first resistance element with a larger resistance value than the parasitic resistance of the inductance element between the first terminal and the second terminal, is coupled in serial with the capacitive element between the first terminal and the second terminal.