Delay-Locked Loop Delay Line With PVT-Stable Clock Synchronization
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Solution Overview
Problem
Conventional delay locked loop (DLL) circuits in semiconductor memory devices are sensitive to variations in process, voltage, and temperature (PVT), leading to instability and increased power consumption, especially in high-frequency operations.
Innovation Solution
A DLL circuit with a delay line that uses impedance calibration codes to control transistors and maintain a predetermined delay, reducing sensitivity to PVT variations, and includes a replica circuit to mimic actual clock path conditions, thereby stabilizing the clock signal and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DLL circuits are used to synchronize internal clock with external clock, then phase synchronization is achieved, but sensitivity to PVT variations increases leading to instability
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the delay amount of delay elements based on detected PVT variations. The control circuit modifies operational parameters (delay amounts) of individual delay elements to compensate for PVT effects, thereby maintaining stable DLL operation across varying process, voltage, and temperature conditions.
Solution Approach 2:
The patent implements feedback mechanisms where the actual delay amount is detected and compared against target values. The control circuit uses this feedback information to generate control signals that adjust the delay elements, creating a closed-loop system that continuously compensates for PVT variations and maintains synchronization stability.
2Adaptability or versatility
If delay range is increased to meet wide operation speed requirements, then frequency coverage from 400 MHz to 1.6 GHz is achieved, but circuit complexity increases
Solution Approach 1:
The patent divides the delay line into multiple independent delay elements, each contributing a specific delay amount. This segmentation allows the total delay to be adjusted in fine increments across a wide frequency range while keeping each individual element relatively simple, thereby achieving high adaptability without excessive overall complexity.
Solution Approach 2:
The patent employs dynamically controllable delay elements whose delay amounts can be adjusted in real-time based on operation frequency requirements. This dynamic adjustment capability enables the DLL to adapt to a wide frequency range (400 MHz to 1.6 GHz) using a unified circuit structure rather than requiring multiple fixed-delay circuits.
3Speed
If fine delay adjustment capability is provided to synchronize data with clock, then operation speed is improved, but number of delay cells increases
Solution Approach 1:
The patent achieves fine delay adjustment by changing the operational parameters (delay amounts) of existing delay elements through control signals, rather than adding more physical delay cells. The control circuit selectively adjusts the delay contribution of each element to achieve precise total delay matching, thereby obtaining fine adjustment capability without proportionally increasing the number of cells.
Solution Approach 2:
The patent replaces the mechanical approach of adding more physical delay cells with a control-based system that adjusts the electrical characteristics (delay amounts) of existing cells. This substitution uses control signals and parameter modulation instead of purely structural expansion, reducing the growth of circuit complexity while maintaining fine delay adjustment capability for high-speed operation.
Data Source
AI summary
A delay locked loop circuit is disclosed. The circuit includes a phase detector for comparing the phase of an input clock signal with the phase of a feedback clock signal that is fed back into the phase detector, and for outputting a detection signal. The circuit also includes a control circuit unit for controlling a delay line in response to the detection signal, a delay line for delaying the input clock by a predetermined amount of delay in response to output impedance calibration codes applied to the delay line, and a replica circuit configured to have the same delay conditions as those of an actual clock path to a circuit of the semiconductor device, to receive a delay clock signal of the delay line, and to generate the feedback clock signal.