Programmable Oscillator Calibration Using USB Data Stream Timing
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Solution Overview
Problem
Existing data transmission systems require external precise clock components, increasing costs and needing additional pins, and conventional frequency calibration methods are slow, making them unsuitable for quick and automatic frequency adjustments in programmable oscillators.
Innovation Solution
A frequency calibration method and device for programmable oscillators that automatically calibrate oscillation frequency using a USB data stream, eliminating the need for external clock components by counting oversampling numbers and accumulated bit numbers to adjust the clock signal frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external precise clock components are used to provide reference frequency, then frequency stability is improved, but system cost and device complexity increase
Solution Approach 1:
The system uses itself to calibrate its frequency by comparing the oscillation frequency against the data stream rate, eliminating the need for external precise clock components. The frequency calibration device measures the actual data transmission rate and adjusts the programmable oscillator accordingly, making the system self-sufficient for frequency reference.
Solution Approach 2:
The invention extracts the frequency reference function from external components and relocates it within the system by using the data stream itself as the reference. This removes the dependency on external crystal resonators or ceramic resonators, simplifying the overall system architecture.
2Measurement precision
If external precise clock components are used, then frequency accuracy is improved, but the number of required pins increases
Solution Approach 1:
The data stream serves multiple functions: it is both the information carrier and the frequency reference. By using the same data stream for both purposes, the system eliminates the need for separate external clock components and their associated communication pins, reducing pin count while maintaining frequency accuracy.
3Measurement precision
If conventional PLL or DLL calibration methods are used, then frequency matching is improved, but calibration time increases
Solution Approach 1:
The invention skips the lengthy iterative adjustment process of conventional PLL or DLL calibration by directly measuring the frequency deviation using the data stream and applying immediate correction. This rushes through the calibration process in a single measurement-correction cycle rather than requiring multiple iterative adjustments.
Solution Approach 2:
The system performs preliminary measurement of the frequency deviation against the data stream rate before making the frequency adjustment. This preliminary action allows for direct calculation of the required correction amount, avoiding the trial-and-error approach of conventional methods and reducing overall calibration time.
4Device complexity
If built-in oscillator is used without external reference, then device complexity is reduced, but frequency drift due to environmental changes increases
Solution Approach 1:
The system establishes a feedback loop where the actual frequency deviation is continuously measured against the data stream rate and used to adjust the programmable oscillator. This feedback mechanism compensates for environmental drift by constantly comparing and correcting the frequency, maintaining stability without requiring external reference components.
Data Source
AI summary
A frequency calibration method for a programmable oscillator includes the steps of: counting an oversampling number of an oversampling signal and estimating an accumulated bit number of a USB data stream according to the oversampling signal; calculating a difference between the oversampling number and M times of the accumulated bit number when the accumulated bit number is larger than a predetermined value; and determining a frequency calibration step of the oversampling signal according to the difference. The present invention further provides a frequency calibration device for a programmable oscillator.