Method and system for short-circuit current modeling in CMOS integrated circuits
First Claim
1. A method for modeling characteristics of a logical circuit, comprising:
- receiving input of a first plurality of values corresponding to points on an input voltage waveform of said logical circuit at discrete times, wherein said first plurality of values is a non-linear representation of said input voltage waveform;
receiving input of a second plurality of values corresponding to points on an output voltage waveform of said logical circuit at said discrete times;
selecting a particular one of said plurality of short-circuit current values;
calculating a plurality of short-circuit current values forming a polygonal model of current through a given one of a complementary pair of transistors within said logical circuit for said discrete times in conformity with a model of said given transistor, a corresponding one of said first plurality of values, and a corresponding one of said second plurality of values, wherein a peak value of said polygonal model is equal to said selected particular one of said plurality of short-circuit current values, and wherein said polygonal model has a width equal to a time difference between a last one of said discrete times and a first one of said discrete times; and
displaying a result of said calculating.
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Abstract
A method and system for short-circuit current modeling in CMOS circuit provides improved accuracy for logic gate power dissipation models in computer-based verification and design tools. The model determines the short circuit current for each complementary pair within a CMOS circuit. Input and output voltage waveforms provided from results of a timing analysis are used to model the behavior one device of the complementary pair. The device is selected as the limiting device (the device transitioning to an “off state) from the direction of the logic transition being modeled, which is also the device that is not charging or discharging the output load. Therefore, the current through the selected device can be determined from the input and output waveforms and is equal to the short-circuit current prior to the saturation of the selected device. One or more short-circuit current points can be determined from the model and used to generate a polygonal waveform model of the short-circuit current, or can be used along with the width (period) of the waveform to calculate short-circuit power dissipation directly.
26 Citations
27 Claims
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1. A method for modeling characteristics of a logical circuit, comprising:
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receiving input of a first plurality of values corresponding to points on an input voltage waveform of said logical circuit at discrete times, wherein said first plurality of values is a non-linear representation of said input voltage waveform; receiving input of a second plurality of values corresponding to points on an output voltage waveform of said logical circuit at said discrete times; selecting a particular one of said plurality of short-circuit current values; calculating a plurality of short-circuit current values forming a polygonal model of current through a given one of a complementary pair of transistors within said logical circuit for said discrete times in conformity with a model of said given transistor, a corresponding one of said first plurality of values, and a corresponding one of said second plurality of values, wherein a peak value of said polygonal model is equal to said selected particular one of said plurality of short-circuit current values, and wherein said polygonal model has a width equal to a time difference between a last one of said discrete times and a first one of said discrete times; and displaying a result of said calculating. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A computer program product for use with a workstation computer, wherein said computer program product comprises a storage media containing program instructions for execution within said workstation computer for modeling characteristics of a logical circuit, and wherein said program instructions comprise program instructions for:
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receiving input of a first plurality of values corresponding to points on an input voltage waveform of said logical circuit at discrete times, wherein said first plurality of values is a non-linear representation of said input voltage waveform; receiving input of a second plurality of values corresponding to points on an output voltage waveform of said logical circuit at said discrete times; selecting a particular one of said plurality of short-circuit current values; calculating a plurality of short-circuit current values forming a polygonal model of current through a given one of a complementary pair of transistors within said logical circuit for said discrete times in conformity with a model of said given transistor, a corresponding one of said first plurality of values, and a corresponding one of said second plurality of values, wherein a peak value of said polygonal model is equal to said selected particular one of said plurality of short-circuit current values, and wherein said polygonal model has a width equal to a time difference between a last one of said discrete times and a first one of said discrete times; and displaying a result of said calculating. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A workstation comprising:
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a memory for storing program instructions and data values for modeling characteristics of a logical circuit; a processor for executing said program instructions, wherein said program instructions comprise program instructions for receiving input of a first plurality of values corresponding to points on an input voltage waveform of said logical circuit at discrete times, wherein said first plurality of values is a non-linear representation of said input voltage waveform; receiving input of a first plurality of values corresponding to points on an input voltage waveform of said logical circuit at discrete times, wherein said first plurality of values is a non-linear representation of said input voltage waveform; receiving input of a second plurality of values corresponding to points on an output voltage waveform of said logical circuit at said discrete times; selecting a particular one of said plurality of short-circuit current values; calculating a plurality of short-circuit current values forming a polygonal model of current through a given one of a complementary pair of transistors within said logical circuit for said discrete times in conformity with a model of said given transistor, a corresponding one of said first plurality of values, and a corresponding one of said second plurality of values, wherein a peak value of said polygonal model is equal to said selected particular one of said plurality of short-circuit current values, and wherein said polygonal model has a width equal to a time difference between a last one of said discrete times and a first one of said discrete times; and displaying a result of said calculating. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification