Oscillator Capacitor Array Dithering for Linear Temperature Compensation
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Solution Overview
Problem
Existing temperature compensation oscillators face challenges in maintaining linearity of capacitance values due to parasitic capacitance and manufacturing variations, which affects the accuracy of temperature compensation for oscillation frequencies.
Innovation Solution
A circuit device with a processing circuit that generates capacitance control data, which is subjected to dithering to switch the capacitance value of a variable capacitance circuit between two values in a time division manner, improving the linearity of the capacitance value and thus enhancing the accuracy of temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If binary-weighted capacitors are used in the capacitor array, then the number of capacitance elements can be reduced, but the linearity of the capacitance value deteriorates due to parasitic capacitance and manufacturing variations
Solution Approach 1:
The patent applies dithering technology to periodically switch between adjacent capacitance values (e.g., 7C and 8C) at a high frequency. This periodic switching creates an average capacitance value that improves linearity while maintaining the compact binary-weighted capacitor structure. The fast switching makes the capacitance change imperceptible to the oscillation circuit, effectively linearizing the capacitance-output characteristic.
2Area of stationary object
If binary-weighted capacitors are used, then the capacitor array size is reduced, but temperature compensation accuracy deteriorates at boundary points where capacitance configurations change
Solution Approach 1:
At boundary points where capacitance configuration changes (e.g., transitioning from 7C to 8C), the patent employs dithering to rapidly switch between the two adjacent capacitance values. This periodic action smooths out the discontinuity and maintains accurate temperature compensation at these critical transition points, preventing degradation of compensation accuracy.
Solution Approach 2:
The patent dynamically changes the capacitance value parameter by switching between adjacent binary-weighted capacitor configurations. By using dithering to create intermediate average values, the system achieves finer resolution in capacitance control and maintains accurate temperature compensation across the entire operating range, including at boundary points.
Data Source
AI summary
A circuit device includes an oscillation circuit and a processing circuit that generates capacitance control data. The oscillation circuit includes a variable capacitance circuit whose capacitance value is variably controlled based on the capacitance control data, and an oscillation frequency thereof is controlled based on the capacitance value of the variable capacitance circuit. The variable capacitance circuit includes a capacitor array. The capacitor array includes a plurality of capacitors each having a binary-weighted capacitance value, and a plurality of switches that are on-off controlled based on the capacitance control data. The processing circuit outputs the capacitance control data, which is subjected to dithering, so as to switch the capacitance value of the variable capacitance circuit between a first capacitance value and a second capacitance value in a time division manner.