Coarse Lock Detection in DLLs With Adaptive Lock Range
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Solution Overview
Problem
Existing skew reduction techniques using phase-locked loops (PLL) or delay-locked loops (DLL) face challenges in maintaining stability and reducing jitter, especially when system bandwidth increases and external noise affects the locking performance.
Innovation Solution
A coarse lock detector and a delay-locked loop that dynamically adjust the lock range based on the number of edges counted in multiphase clocks, enabling a dynamic phase detector to fine-tune the delay elements and maintain lock stability by varying the lock range in response to noise fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed lock range is used in the coarse lock detector, then the device complexity is reduced, but the stability deteriorates due to frequent locking and unlocking events under noise conditions
Solution Approach 1:
The patent applies dynamics by making the lock range variable rather than fixed. The coarse lock detector dynamically adjusts the lock range based on the number of edges counted in multiphase clocks, allowing the system to adapt to noise conditions and prevent frequent locking/unlocking events while maintaining reasonable device complexity.
2Reliability
If the lock range is widened to prevent frequent unlocking under noise, then the stability is improved, but the productivity deteriorates due to slower lock acquisition time
Solution Approach 1:
The patent implements periodic action by using multiple counting cycles of the input reference clock to determine whether to adjust the lock range. The lock range is not changed continuously but periodically based on edge counts accumulated over N cycles, which balances stability improvement with acceptable lock acquisition time.
Solution Approach 2:
The dynamic adjustment of lock range allows the system to widen the range only when needed (when edge count indicates potential unlocking risk), rather than maintaining a constantly wide range. This dynamic behavior improves stability only when necessary while preserving fast lock acquisition during normal operation.
3Productivity
If the lock range is narrowed to speed up lock acquisition, then the productivity is improved, but the stability worsens due to increased sensitivity to noise-induced unlocking
Solution Approach 1:
The system dynamically adjusts the lock range based on real-time edge counting results. When the edge count falls within the expected range over N cycles, the system maintains a narrow lock range for fast acquisition. When the edge count deviates, indicating potential noise-induced unlocking, the system widens the lock range to prevent unlocking, thus balancing speed and stability adaptively.
Data Source
AI summary
A coarse lock detector is disclosed. The course lock detector uses an initial lock range to determine course lock, and once course lock is achieved, uses a modified lock range to determine course lock.