Multi-Phase Clock Generation Using DLL Feedback Against Duty Cycle Error
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Solution Overview
Problem
High-speed data transmission in electronic devices is affected by duty cycle errors in clock signals, leading to jitter and inaccurate timing, which becomes more significant at higher frequencies, potentially causing clock signal failures and data transmission errors.
Innovation Solution
A clock synchronization circuit generates reference signals from the rising edges of an external clock signal, with a 180° phase difference and half the frequency, to produce four-phase clock signals that are immune to duty cycle errors, ensuring accurate falling edge information and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-frequency clock signals are used for high-speed data transmission, then data transmission speed is improved, but duty cycle errors cause jitter and timing inaccuracies
Solution Approach 1:
A delay-locked loop (DLL) is introduced as an intermediary mechanism between the external clock signal and the internal data transmission circuits. The DLL generates phase-aligned clock signals by detecting the actual rising edges of the external clock and adjusting internal delay elements, thereby eliminating duty cycle errors and jitter while maintaining high-frequency operation for high-speed data transmission
2Speed
If high-frequency clock signals are used, then data transmission speed is improved, but power consumption increases
Solution Approach 1:
The system dynamically adjusts delay element configurations based on detected clock signal characteristics. The DLL continuously monitors the external clock signal and adjusts internal delay elements in real-time, allowing the system to optimize power consumption by using minimal delay adjustments while maintaining high-frequency operation for high-speed data transmission
3Device complexity
If conventional clock signal generation is used, then device complexity is low, but clock failures occur due to duty cycle errors
Solution Approach 1:
A feedback mechanism is implemented where the DLL detects the actual rising edges of the external clock signal and uses this information to adjust internal delay elements. This feedback loop continuously corrects phase alignment and eliminates duty cycle errors, significantly improving clock signal stability and preventing clock failures while maintaining relatively simple circuit implementation
Data Source
AI summary
An apparatus and method for multi-phase clock generation are disclosed. One embodiment of the apparatus includes a module generating first and second intermediate signals delayed from first edges of a clock signal having a first frequency. Each of the first and second intermediate signals has a second frequency that is half of the first frequency. The first and second intermediate signals have a phase difference of 180° from each other. The apparatus also includes a first delay line delaying the first intermediate signal by a first delay amount; a second delay line delaying the first intermediate signal by a second delay amount; a third delay line delaying the second intermediate signal by a third delay amount; and a fourth delay line delaying the second intermediate signal by a fourth delay amount. The apparatus also includes a closed feedback loop for detecting and adjusting the second and fourth delay amount.