Oscillator Auto Trimming Using Index Values for Fast Frequency Calibration
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Solution Overview
Problem
Existing auto trimming devices for oscillators face challenges in accurately measuring high-frequency oscillators due to parasitic RC components, which distort waveforms and limit measurement accuracy, and require increased measuring time when using frequency dividers to mitigate distortion.
Innovation Solution
An auto trimming device that includes an oscillator, a subtractor, an index value selector, an index value register, and an embedded memory to calculate and store a target index value, allowing for precise trimming of the oscillator frequency by detecting differences between expected and actual clock signals, using a divider and binary searcher to optimize index value calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency divider is added to reduce waveform distortion, then measurement accuracy is improved, but measuring time is increased
Solution Approach 1:
The patent uses an index value that copies or represents the oscillator frequency characteristics without requiring actual frequency division. The index value selector generates an index value based on the oscillator clock signal, which indirectly represents the frequency information needed for trimming, avoiding the time-consuming frequency division process while maintaining measurement accuracy
Solution Approach 2:
The patent replaces the mechanical frequency division approach with an electronic index value calculation system. Instead of physically dividing the frequency signal through multiple stages, the system uses a subtractor to calculate the difference between expected and actual clock counts, then uses an index value selector to generate a trimming index, substituting complex signal processing with simpler arithmetic operations
2Loss of time
If direct measurement of high frequency oscillator is performed, then measuring time is reduced, but measurement accuracy deteriorates due to parasitic RC components
Solution Approach 1:
The patent introduces an intermediary measurement approach by counting clock cycles over a fixed period defined by a reference time signal instead of directly measuring the high-frequency waveform. The subtractor acts as an intermediary that calculates the difference between expected and actual clock counts, providing accurate frequency information without directly encountering the parasitic RC distortion issues of high-frequency direct measurement
Solution Approach 2:
The patent performs preliminary action by using a reference time signal to pre-define the measurement period before actual frequency measurement occurs. This allows the system to count oscillator clocks over a known, controlled time interval, eliminating the need for direct high-frequency waveform capture and subsequent processing that would be affected by parasitic effects
Data Source
AI summary
An auto trimming device includes an oscillator configured to generate an oscillator clock signal, a subtractor configured to receive an expected value for a target frequency and the oscillator clock signal, configured to output a difference value between the expected value and the oscillator clock signal, an index value selector configured to calculate a unit index value using the difference value and configured to detect and output a target index value from the unit index value, an index value register configured to output an oscillator trimming code corresponding to the target index value to the oscillator, and an embedded memory configured to store the oscillator trimming code as a target oscillator trimming code for the target frequency.