Adaptive wire adjustment for bounded skew clock distribution network using quadratic tree

Recently, a new approach, called Adaptive Wire Adjustment (AWA), was proposed for the synthesis of Clock Distribution Networks (CDNs) in order to cope with modifications required in the design process. The main drawback of the AWA is its slow convergence. In this paper, we propose to use a quadratic tree instead of a binary tree in order to speed up the AWA´s convergence. The proposed approach reduces the skew iteratively by selecting a balancing node (BN), selecting the topology of connecting the BN to its children, and adjusting the edges so that the skew gets smaller, In addition to the faster convergence, the quadratic tree structure offers a topology flexibility that helps to reduce the wire length further. The procedure of selecting the connection topology and determining the edge adjustments are based on the Elmore delay model. The performance of the proposed algorithm is investigated using different random sets of registers. The results show that the number of iterations can be reduced effectively as the number of clock pins increases. Further, for CDNs of 1024, 4096 and 16384 clock pins, the proposed technique can reduce the CDNs total wire length by 4.9%, 14.7% and 27.6% respectively.