Oscillator Clock Duty Adjustment Without Feedback Noise
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Solution Overview
Problem
Existing clock duty compensation circuits generate noise due to operational amplifier feedback, deteriorating noise characteristics of the clock signal.
Innovation Solution
A circuit device with a clock signal generation circuit, output circuit, test terminal, storage circuit, and duty adjustment circuit that adjusts the duty of the clock signal based on a duty adjustment value, using a method that minimizes noise by measuring difference values between DC voltages of normal and reverse rotation signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an operational amplifier feedback circuit is used for clock duty compensation, then the clock duty can be corrected, but noise is generated and noise characteristics of the clock signal deteriorate
Solution Approach 1:
The patent extracts and removes the operational amplifier feedback circuit from the clock duty compensation system. Instead of using continuous feedback, the invention measures the duty ratio through a test terminal, calculates the correction value, and applies it without maintaining an active feedback loop, thereby eliminating the noise generation source while preserving duty correction functionality
Solution Approach 2:
The patent implements periodic measurement and correction rather than continuous feedback. The duty ratio is measured at specific intervals through the test terminal, and correction values are applied periodically, replacing the continuous operational amplifier feedback with discrete measurement and correction cycles, which reduces noise while maintaining compensation effectiveness
2Measurement precision
If continuous feedback is used for duty compensation, then duty accuracy can be maintained, but measurement errors increase and noise characteristics deteriorate
Solution Approach 1:
The patent performs preliminary measurement of the duty ratio through the test terminal before applying correction. By measuring the actual duty ratio beforehand and calculating the required correction value in advance, the system avoids continuous feedback measurements that accumulate errors, while still achieving accurate duty correction through the pre-calculated adjustment
Data Source
AI summary
A circuit device includes a clock signal generation circuit that generates a clock signal, an output circuit that outputs an output clock signal based on the clock signal, and a clock terminal that outputs the output clock signal. The circuit device further includes a test terminal, a storage circuit that stores a duty adjustment value, and a duty adjustment circuit that adjusts a duty of the clock signal based on the duty adjustment value. The output circuit outputs a first DC voltage based on a normal rotation signal of the clock signal to the test terminal in a first state. The output circuit outputs a second DC voltage based on a reverse rotation signal of the clock signal to the test terminal in a second state.