Delay-Locked Loop Initialization Circuit for Wide-Range Locking
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Solution Overview
Problem
Existing delay-locked loop (DLL) circuits are often designed for fixed or limited frequency ranges, leading to issues with false locking and inadequate performance across a broad range of operating frequencies in high-end electronic devices.
Innovation Solution
A DLL circuit with an initialization circuit that tracks input frequency and PVT variations, using a voltage-controlled delay line and a switched capacitor circuit controlled by non-overlapping reference clock versions to generate an initialization voltage signal, ensuring fast and accurate locking across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DLL circuit is designed for fixed or limited frequency ranges, then false locking and harmonic locking are reduced, but the frequency range and adaptability are limited
Solution Approach 1:
The initialization circuit pre-charges the control voltage node to a predetermined voltage level before the DLL locking process begins. This preliminary action ensures that the delay line starts from a known state that corresponds to a valid lock point, preventing false locking and harmonic locking while enabling the DLL to operate across a broad frequency range.
Solution Approach 2:
The initialization circuit dynamically adjusts the control voltage parameter based on the detected frequency range. By changing the initialization voltage level according to the operating frequency, the circuit maintains reliable locking behavior across different frequency conditions while maximizing adaptability.
2Loss of time
If the delay line is minimized prior to operation, then start-up time is reduced, but locking accuracy may be compromised
Solution Approach 1:
The initialization circuit performs preliminary setup by pre-charging the control voltage to an optimal level before the DLL begins operation. This advance preparation reduces the time required for the DLL to acquire lock while ensuring that the pre-charged voltage corresponds to a valid lock point, thereby maintaining locking accuracy.
Solution Approach 2:
The initialization circuit incorporates feedback mechanisms that monitor the DLL locking status and adjust the initialization voltage accordingly. This feedback ensures that the pre-charge voltage is optimally set to achieve fast locking without compromising accuracy, as the circuit can adapt the initialization parameters based on actual locking conditions.
Data Source
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AI summary
A delay-locked loop (DLL) includes a delay line configured to receive a reference clock signal and a control signal, and generate a first plurality of clock signals. Each clock signal of the first plurality is configured to have a different phase delay relative to the reference clock signal. A phase frequency detector is coupled to the delay circuit and is configured to receive a first clock signal and a second clock signal of the first plurality, and generate up and down control signals. A charge pump is coupled to receive the up and down control signals and generates a charge pump current based on the up and down control signals. An output of the charge pump is coupled to the delay line at a voltage control node. An initialization circuit is coupled to the voltage control node and is configured to generate an initialization voltage based on the reference clock signal frequency.