Method and apparatus for placing repeaters in a network of an integrated circuit

Abstract

A method of inserting repeaters into a network to improve timing characteristics of the network. Extraction and timing tools provide an RC network description and a slack report describing electrical and timing characteristics of a network. The timing characteristics include required arrival times of a signal generated at a source to each of the sinks of the network. A maximum slew rate is also defined at each of the sinks. Initial candidate locations for insertion of repeaters is determined. For a given set of legal repeater sizes, one or more sets of midvalue repeater sizes are determined which are used in successive approximation to identify actual repeater sizes to be considered at each of the candidate locations. At each candidate location, capacitance, required arrival time, and slew rate value (c, q, s) are determined in a bottom-up procedure. Suboptimal and invalid (c, q, s) choices at each candidate location are eliminated during successive iterations of the bottom-up procedure until the source node is reached. Further, one or more of the candidate locations are also eliminated. When the source device is reached, the (c, q, s) values are determined at the source for the given size of the source. The particular combination of (c, q, s) values at the descendant nodes relative to the source that provide a maximum q value at the source are selected, and this procedure is repeated in a top-down traversal to identify the best solution for the net for the particular repeater sizes being used.