Method for estimating interconnect delays in integrated circuits
First Claim
1. For an original circuit having an original driving device connected to an original driving node and another node connected to said original driving node through an impedance network, a method of determining an approximate delay time after said original driving device is turned on at which a voltage at said another node reaches a predetermined value, comprising the steps of:
- for a substitute circuit having a substitute driving device connected to a substitute driving node and specified by a predetermined set of parameters, determining for a multiplicity of different sets of values of said predetermined set of parameters, using a computer simulator, voltage waveforms expected at said substitute driving node in response to said substitute driving device being turned on, and retrievably storing discrete-time representations of said voltage waveforms;
determining a set of values of said predetermined set of parameters for which delay characteristics of said substitute circuit approximate delay characteristics of said original circuit, and from said discrete-time representations of said voltage waveforms, determining a voltage waveform corresponding to said set of values;
scaling said voltage waveform such that a resulting scaled voltage waveform approximates a voltage waveform expected at said original driving node of said original driving circuit in response to said original driving device being turned on;
determining an approximate analytical expression for said scaled voltage waveform; and
predicting said approximate delay time of said original circuit using said approximate analytical expression.
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Abstract
A method for predicting circuit interconnect delays in circuits of the type that have a driving device attached to an input node of a network having a plurality of nodes, with the driving device changing states from time to time so as to impose on the network a voltage different from the previous voltage of the network. The method includes the steps of estimating the waveform on the input node and predicting the waveforms on other nodes of the network on the basis of the estimated input node waveform.
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Citations
24 Claims
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1. For an original circuit having an original driving device connected to an original driving node and another node connected to said original driving node through an impedance network, a method of determining an approximate delay time after said original driving device is turned on at which a voltage at said another node reaches a predetermined value, comprising the steps of:
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for a substitute circuit having a substitute driving device connected to a substitute driving node and specified by a predetermined set of parameters, determining for a multiplicity of different sets of values of said predetermined set of parameters, using a computer simulator, voltage waveforms expected at said substitute driving node in response to said substitute driving device being turned on, and retrievably storing discrete-time representations of said voltage waveforms; determining a set of values of said predetermined set of parameters for which delay characteristics of said substitute circuit approximate delay characteristics of said original circuit, and from said discrete-time representations of said voltage waveforms, determining a voltage waveform corresponding to said set of values; scaling said voltage waveform such that a resulting scaled voltage waveform approximates a voltage waveform expected at said original driving node of said original driving circuit in response to said original driving device being turned on; determining an approximate analytical expression for said scaled voltage waveform; and predicting said approximate delay time of said original circuit using said approximate analytical expression. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification