Duty Cycle Correction Circuit for Stable High-Speed Memory Clocks
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Solution Overview
Problem
In memory systems, maintaining accurate temporal synchronization between clock and data signals becomes challenging due to increased loads on the bus and higher data transmission frequencies, leading to potential signal distortion and errors.
Innovation Solution
A semiconductor device with a duty cycle correction circuit and delay locked loop (DLL) that adaptively compensates for changes in clock duty caused by process skew, temperature, and voltage variations, maintaining a constant 5:5 duty ratio through a duty correction circuit that includes a divider, delay units, and inverters to generate an adjusted clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data transmission frequency is increased to improve productivity, then data transmission speed is improved, but temporal synchronization accuracy deteriorates due to signal distortion and bus load increases
Solution Approach 1:
The patent changes the parameter of clock duty cycle from its original distorted state back to a standardized 50% duty cycle. The duty cycle correction circuit adjusts the width of clock pulses to maintain equal high and low periods, compensating for distortion caused by high-frequency operation and bus loading. This parameter adjustment restores temporal synchronization accuracy while allowing high-speed data transmission to continue.
2Measurement precision
If clock duty cycle is corrected to maintain temporal synchronization, then synchronization accuracy is improved, but device complexity increases due to additional correction circuits
Solution Approach 1:
The patent introduces a duty cycle correction circuit as an intermediary component between the clock source and the data transmission system. This intermediary circuit receives the distorted clock signal, corrects its duty cycle to 50%, and outputs the corrected clock signal. By placing this correction stage in the signal path, the patent achieves synchronization accuracy without requiring fundamental redesign of the entire data transmission system.
Solution Approach 2:
The duty cycle correction function is segmented into distinct operational stages: detection of duty cycle distortion, calculation of correction amount, and generation of corrected clock signal. The correction circuit is further divided into functional blocks including delay units, logic gates, and control logic. This segmentation allows each component to perform its specific function efficiently and enables independent optimization of each stage.
3Reliability
If duty cycle correction is implemented to reduce signal distortion, then transmission reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The duty cycle correction circuit is designed to automatically detect and correct its own duty cycle distortion without requiring external calibration or adjustment. The circuit monitors its output clock signal and dynamically adjusts internal delay elements to maintain a 50% duty cycle. This self-correcting capability reduces the need for precise manufacturing tolerances, as the circuit compensates for process variations through its own operation.
Solution Approach 2:
The correction circuit incorporates feedback mechanisms that monitor the duty cycle of the output clock signal and adjust correction parameters accordingly. By continuously measuring the actual duty cycle and comparing it to the target 50% value, the circuit dynamically modifies its correction amount to compensate for manufacturing variations, temperature drift, and voltage changes. This feedback control reduces sensitivity to manufacturing precision requirements.
Data Source
AI summary
A semiconductor device includes a delay locked loop (DLL) configured to output a first correction value corresponding to a single cycle of a clock and a duty correction circuit including a divider configured to divide the clock in half to generate a divided clock, delay the divided clock by a delay value corresponding to a half cycle of the clock to generate a delayed clock, and generate an adjusted clock having a duty ratio of 5:5 based on the divided clock and the delayed clock. The delay value is adjusted or changed based on the first correction value.