Monotonic Delay Line with Phase Interpolation for Fast DLL Locking
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Solution Overview
Problem
Existing clock placement systems in I/O systems with forwarded clock architectures face challenges in achieving precise clock edge placement under varying environmental conditions, particularly at high frequencies, due to limitations in power consumption, start-up issues, and non-monotonic delay steps, which affect data transfer rates and accuracy.
Innovation Solution
A clock placement architecture utilizing a monotonic delay line with phase interpolation and a finite state machine (FSM) to provide precise, monotonic delay steps and duty cycle correction, allowing for continuous updates without interfering with data transfers, and incorporating sensors to detect safe zones for clock edge placement, reducing power consumption and improving lock time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an analog DLL is used for clock placement, then clock edge placement can be achieved, but power consumption increases and start-up performance deteriorates
Solution Approach 1:
The patent replaces the analog DLL system with a digital delay line system. The digital delay line uses digital logic circuits (D-latches, multiplexers, delay elements) to achieve clock edge placement instead of analog continuous adjustment. This substitution fundamentally changes the system from analog to digital domain, resolving the contradiction by achieving precise placement through digital control while maintaining lower power consumption characteristics.
Solution Approach 2:
The patent implements a digital delay line with configurable delay stages that can be controlled by digital parameters. The delay amount is adjusted by changing digital control words that select different delay paths and stage combinations. This parameter-based control enables precise clock edge placement while allowing the system to operate in different power states, resolving the contradiction between precision and power consumption.
2Measurement precision
If an analog DLL is used for clock placement, then clock edge placement can be achieved, but start-up and re-start performance deteriorates
Solution Approach 1:
The patent incorporates a start-up circuit that pre-configures the digital delay line before the main clock signal is fully established. The start-up circuit generates initial control signals to set the delay line in a known good state, ensuring immediate correct operation upon start-up or re-start. This preliminary action eliminates the slow convergence issues of analog DLLs and achieves fast lock times.
Solution Approach 2:
The digital delay line system includes self-calibration and self-correction mechanisms that automatically adjust the delay parameters without external intervention. The system monitors its own operation and makes real-time adjustments to maintain optimal performance, enabling fast re-start capability after clock interruptions without requiring manual recalibration or complex analog recovery circuits.
3Adaptability or versatility
If a delay line with non-monotonic delay steps is used, then delay adjustment can be achieved, but clock edge alignment deteriorates
Solution Approach 1:
The patent divides the delay line into multiple discrete delay stages, each contributing a specific delay amount. By segmenting the total delay into manageable stages with monotonic incrementing values, the system achieves both wide adjustment range and precise monotonic control. Each stage can be independently controlled, allowing the clock edge to be aligned precisely without the non-monotonic behavior that causes misalignment.
Solution Approach 2:
The patent implements a dynamic delay control mechanism where the delay line parameters can be continuously adjusted in real-time based on feedback from the system. The delay stages are controlled by dynamic digital signals that can be modified on-the-fly, allowing the system to adapt to changing conditions while maintaining monotonic delay progression for accurate clock edge alignment throughout the adjustment range.
Data Source
AI summary
A delay line has at least four delay stages coupled together in a series, two multiplexers, and a phase interpolator. The first multiplexer has a first input coupled to an output of the first delay stage, and a second input coupled to an output of the third delay stage. Similarly, the second multiplexer has a first input coupled to an output of the second delay stage, and a second input coupled to an output of the fourth delay stage. The phase interpolator is coupled to outputs of the first and second multiplexers, and has an output.