Digital Temperature-Compensated Oscillator Frequency Control
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Solution Overview
Problem
Existing oscillators, such as TCXO and OCXO, face challenges in achieving high precision frequency-temperature characteristics due to correction errors from variations in analog circuits and delays in data transfer between A/D conversion, processing, and oscillation circuits.
Innovation Solution
A circuit device with an A/D conversion circuit, processing circuit, and oscillation signal generation circuit that converts control voltage and temperature detection voltage into frequency control data, using a resonator with a variable capacitor for precise oscillation frequency generation, and a fractional-N type PLL circuit for phase comparison, minimizing the need for separate frequency and temperature compensation capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second temperature voltage generation circuit is provided for correction, then frequency-temperature characteristics are improved, but correction errors occur due to analog circuit variations
Solution Approach 1:
The patent replaces the analog temperature compensation circuit with a digital processing system. The A/D conversion circuit converts the control voltage to digital data, the processing circuit performs digital addition of temperature compensation data and control voltage data, and the D/A conversion circuit converts the result back to voltage. This digital substitution eliminates correction errors caused by analog circuit variations while maintaining frequency-temperature characteristics.
2Object-affected harmful factors
If separate terminals for digital I/F and clock signal output are disposed on different sides, then noise is reduced, but data transfer delay increases
Solution Approach 1:
The patent combines the digital I/F terminal and clock signal output terminal on the same side of the circuit device. This merging of terminal locations simultaneously achieves noise reduction through proper separation of signal types and minimizes data transfer delay by reducing the physical distance between related terminals, thereby resolving the contradiction between noise reduction and speed.
Data Source
AI summary
A circuit device includes a control voltage input terminal to which a control voltage is inputted, an A/D conversion circuit A/D-converting the control voltage to generate control voltage data and A/D-converting a temperature detection voltage from a temperature sensor to generate temperature detection data, a processing circuit generating temperature compensation data of an oscillation frequency based on the temperature detection data and performing addition processing of the temperature compensation data and the control voltage data to generate frequency control data of the oscillation frequency, and an oscillation signal generation circuit generating an oscillation signal of the oscillation frequency set by the frequency control data, using the frequency control data and a resonator.