DDR Clock Duty Cycle Correction With Asynchronous Prime-Ratio Sampling
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Solution Overview
Problem
Existing clock duty cycle correction techniques in DDR memory systems are inefficient, slow, and inaccurate, particularly when measuring and adjusting duty cycles in a large number of target clock signals, leading to significant errors and imprecision.
Innovation Solution
A duty cycle correction method using a well-controlled asynchronous sampling clock with a prime number ratio to periodically sample the target clock signal, allowing for rapid and accurate measurement and adjustment of duty cycles based on a single measurement cycle, minimizing the number of required samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional duty cycle correction techniques are used, then the correction process can be implemented, but the measurement and adjustment are slow and inaccurate, leading to significant errors
Solution Approach 1:
The patent employs periodic sampling of the target clock signal using an asynchronous sampling clock. By sampling at specific periodic intervals determined by a prime number ratio, the system efficiently captures duty cycle information without requiring continuous monitoring, thus achieving accurate measurement while minimizing time loss.
Solution Approach 2:
The patent changes the sampling parameters by using an asynchronous sampling clock with a prime number ratio relative to the target clock frequency. This parameter change enables the system to measure multiple duty cycle points within a single measurement cycle, significantly improving measurement speed and accuracy simultaneously.
2Measurement precision
If multiple samples are taken to improve measurement accuracy, then the precision increases, but the time required for correction increases significantly
Solution Approach 1:
The system performs periodic sampling at optimized intervals using an asynchronous sampling clock. This allows multiple duty cycle measurements to be completed within a single measurement cycle, achieving high precision without sacrificing correction speed.
Solution Approach 2:
The asynchronous sampling clock serves multiple functions simultaneously: it generates sampling pulses, determines measurement timing, and enables multi-point duty cycle measurement within a single cycle. This multi-functionality allows the system to achieve high precision measurements while maintaining fast correction speed.
3Measurement precision
If a well-controlled asynchronous sampling clock with prime number ratio is used, then measurement accuracy and correction speed are improved, but the system complexity increases
Solution Approach 1:
The patent utilizes a prime number ratio between the sampling clock and target clock frequencies as a key parameter. This specific parameter relationship simplifies the sampling mathematics and enables accurate duty cycle measurement without requiring complex synchronization mechanisms, thus improving precision while managing system complexity.
4Reliability
If traditional sampling methods are used, then the system can operate, but significant residual errors remain and data transmission rates are limited
Solution Approach 1:
The system measures the actual duty cycle of the target clock signal and uses this feedback information to adjust and correct the duty cycle. By implementing a feedback mechanism that continuously monitors and corrects duty cycle deviations, the system achieves high precision correction and improves data transmission reliability.
Solution Approach 2:
The periodic sampling approach allows the system to regularly measure and correct duty cycle errors, maintaining high precision over time. This periodic correction mechanism ensures that residual errors are minimized and data transmission reliability is maintained at high rates.
Data Source
AI summary
Examples may include techniques for using a sample clock to measure a duty cycle by periodic sampling a target clock signal based on a prime number ratio of a reference clock frequency. The reference clock frequency used to set a measurement cycle time over which the duty cycle is to be measured. A magnitude of a duty cycle error as compared to a programmable target duty cycle is determined based on the measured duty cycle and the duty cycle is adjusted based, at least in part, on the magnitude of the duty cycle error.