Early Tapoff Selection for H-Tree Clock Skew
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Solution Overview
Problem
In electronic design automation, balanced clock structures in circuit designs face challenges with early sinks that require different timing requirements, leading to clock skew and jitter, which existing methods struggle to address effectively.
Innovation Solution
The method involves automatically adding early tapoffs to a balanced clock structure to compensate for early sinks by selecting appropriate locations based on various criteria, including buffer locations and path adjustments, to ensure synchronized clock signal delivery across the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a balanced clock structure is used to distribute clock signals, then clock signal synchronization is improved, but early sinks cannot receive clock signals at the required time due to fixed path lengths
Solution Approach 1:
The clock distribution network is segmented into multiple paths with different lengths, allowing early sinks to receive clock signals through shorter paths while other sinks receive them through longer paths, thus satisfying different timing requirements without compromising overall synchronization
Solution Approach 2:
Different path lengths are assigned to different regions or sinks within the clock distribution network, enabling local optimization where early sinks receive clock signals earlier through dedicated shorter paths while maintaining balanced distribution to other sinks
2Loss of time
If early sinks are accommodated by adding early tapoffs to the balanced clock structure, then timing requirements for early sinks are met, but clock skew and jitter increase
Solution Approach 1:
The clock distribution network introduces asymmetric path lengths by adding early tapoffs, creating deliberately unequal paths to satisfy early sink timing requirements while using buffering and delay elements to minimize the resulting asymmetry's impact on clock skew and jitter
Solution Approach 2:
Buffering elements and delay elements are strategically placed to adjust the electrical characteristics and propagation delays of different clock paths, compensating for the asymmetry introduced by early tapoffs and maintaining signal integrity and timing precision
3Loss of time
If existing methods are used to address early sinks in balanced clock structures, then some timing adjustments are possible, but the methods struggle to effectively minimize clock skew and jitter
Solution Approach 1:
Buffering elements and delay elements serve as intermediary components between the clock source and sinks, actively compensating for path length differences and electrical variations to maintain signal quality and minimize skew and jitter while providing flexible timing adjustments for early sinks
Data Source
AI summary
Electronic design automation systems, methods, and media are presented for modifying a balanced clock structure. One embodiment involves accessing a circuit design comprising an H-tree clock distribution network that provides a clock signal to a plurality of sinks. Timing requirements for each sink are identified, and a plurality of early tapoff candidate locations are also identified. A corresponding arrival time adjustment associated with each early tapoff candidate location is estimated for early sinks, and an early tapoff location is selected for each early sink based on the early arrival timing requirement and the arrival time adjustment associated with the tapoff location. In various embodiments, different criteria may be used for selecting the early tapoff location, and updated circuit designs are then generated with a route from early sinks to the early tapoff location selected for each early sink.