Synopsys, Inc.

Harold J Levy

Michael N Misheloff

Xin Wang

A precharacterized cell library for EDA tools includes driver model data includes output current signals indexed by output voltages. The driver model can then generate a model output by interpolating the output current signals using the output voltage to generate an output current. The output current can then be used to generate an updated output voltage across a predetermined time increment. The output current signals can then be interpolated using the updated output voltage to generate a new output current, when can be used to update the output voltage once again across the next time increment. By repeating this process across a time frame for the model output signal, a model output current and output voltage signals can be generated that match the actual output current and voltage signals from a driver in a multi-driver system.

Nonlinear driver model for multi-driver systems

A characterized cell library for EDA tools includes receiver model data that provides two or more capacitance values for a given receiver modeling situation (signal type and operating conditions). The receiver model can then use different capacitance values to generate different portions of the model receiver signal, thereby enabling more accurate matching of actual receiver signal timing characteristics. For example, a two-capacitance receiver model can be generated by using the first capacitance value to match the delay characteristics of an actual receiver, and by using the second capacitance (in light of the use of the first capacitance) to match the slew characteristics of that actual receiver. Because typical EDA timing analyses focus mainly on delay and slew (and not the detailed profile of circuit signals), a two-capacitance receiver model can provide a high degree of accuracy without significantly increasing cell library size and computational complexity.

Non-linear receiver model for gate-level delay calculation

An enhanced library accessible by an EDA tool can include a base curve database and a plurality of curve data sets. Each curve data set refers to a standard cell having certain timing characteristics. To determine those timing characteristics, each curve data set identifies at least one base curve (in the base curve database) as well as a starting current, a peak current, a peak voltage, and a peak time. In one embodiment, each base curve can be normalized. The base curve(s), the starting current, peak current, peak voltage, and peak time can accurately model the functioning of the IC device, e.g. represented by an I(V) curve.

Generating a base curve database to reduce storage cost

A method for generating a linear piecewise representation of a driver output current signal includes segmenting the driver output current signal such that an integral of each segment matches an actual voltage change in corresponding portion of an associated output voltage signal (within a desired tolerance). The beginning and ending current/time values for each segment can then be compiled into the piecewise linear representation of the driver output current signal. A method for generating a model driver output current signal includes conformally mapping first and second sets of precharacterization output current data based on a weighted average of the indexing parameter (e.g., input slew or output capacitance) values for the model driver output signal and the first and second sets of precharacterization data.

Segmentation and interpolation of current waveforms

Nonlinear receiver model for gate-level delay calculation

A system is provided for determining voltage at the output of a gate in an integrated circuit. The system locates a gate within the integrated circuit and looks up a set of output current waveforms as a function of time for different effective capacitances at the gate's output. The system applies each output current waveform to its corresponding effective capacitance to calculate a first set of output voltages and applies each output current waveform to a model of the net coupled to the output of the gate to calculate a second set of output voltages. For each time step in a series of time steps, the system selects an output current waveform for which a voltage in the first set of output voltage waveforms matches a voltage in the second set of output voltage waveforms. The system uses the selected output current waveform to determine the output voltage.

Method and apparatus for determining gate-level delays in an integrated circuit

A computer implemented method of producing a reduced order model of an electronic circuit to model the connection of two or more circuits. Arnoldi reduced order models for nodes of circuits to be interconnected may be computed. A set of modified nodal analysis matrices for the combination of the two circuits may be constructed. A rank one update may be applied to the modified set of nodal analysis matrices to produce a reduced order model of the combined electronic circuits. In this novel manner, a reduced order model for a combination of circuits may be produced from the individual reduced order models of the individual circuits without the need to recompute the reduced order models of the original circuits, and without the need of the original parasitic network models. The resulting reduced order model may be used in a variety ways consistent with well known uses of such matrices within the field of electronic design automation.

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Los Gatos, CA, United States of America

Harold J Levy