Method and system for power node current waveform modeling
First Claim
1. A method for modeling characteristics of a logical circuit block, comprising:
- receiving input of a first plurality of values corresponding to times at which an output voltage of said logical circuit block reaches selected predetermined fractions of a supply voltage; and
generating a second time value for which said output voltage reaches a different predetermined fraction of said supply voltage by multiplying each of said plurality of values by a corresponding one of a set of coefficients that statistically relate said first plurality of input values to said second time value, and summing the multiplied values to produce a resulting time at which said output voltage reaches said different predetermined fraction of said supply voltage.
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Abstract
A method and system for power node current waveform modeling provides improved accuracy for logic gate and functional block power node current models in computer-based verification and design tools. An output voltage waveform is generated, with each point a linear function of a set of input values corresponding to times at which the output voltage reaches predetermined fractional values of the supply voltage. A set of coefficients is used for each point, as each output voltage waveform point has a different linear dependency on the set of input values.
The output voltage waveform model is then differentiated and multiplied by an effective load capacitance to determine the output current waveform. The method and system retain compatibility with existing software by using input values already present in the digital simulation models (e.g., the 70%-30% delay time or delay time from other voltage pairs, and the 50% switch point time) that yield a subset of output voltage points.
The coefficients used in the model are predetermined for the particular circuit from a principle components analysis. The model is highly accurate as the coefficients that determine the linear functions are determined via a principle components analysis that determines the coefficients by factoring input value dependence down to three input variables while maintaining high correlation values between the model and circuit simulations over various input and circuit conditions.
15 Citations
24 Claims
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1. A method for modeling characteristics of a logical circuit block, comprising:
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receiving input of a first plurality of values corresponding to times at which an output voltage of said logical circuit block reaches selected predetermined fractions of a supply voltage; and
generating a second time value for which said output voltage reaches a different predetermined fraction of said supply voltage by multiplying each of said plurality of values by a corresponding one of a set of coefficients that statistically relate said first plurality of input values to said second time value, and summing the multiplied values to produce a resulting time at which said output voltage reaches said different predetermined fraction of said supply voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A computer program product for use with a workstation computer, wherein said computer program product comprises signal bearing media containing program instructions for execution within said workstation computer for modeling characteristics of a logical circuit block, wherein said program instructions comprise program instructions for:
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receiving input of a first plurality of input values corresponding to times at which an output voltage of said logical circuit block reaches selected predetermined fractions of a supply voltage; and
generating a second time value for which said output voltage reaches a different predetermined fraction of said supply voltage by multiplying each of said first plurality of input values by a corresponding one of a set of coefficients that statistically relate said first plurality of input values to said second time value, and summing the multiplied values to produce a resulting time at which said output voltage reaches said different predetermined fraction of said supply voltage. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A workstation comprising:
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a memory for storing program instructions and data values for modeling characteristics of a logical circuit block;
a processor for executing said program instructions, wherein said program instructions comprise program instructions for receiving input of a first plurality of input values corresponding to times at which an output voltage of said logical circuit block reaches selected predetermined fractions of a supply voltage, and generating a second time value for which said output voltage reaches a different predetermined fraction of said supply voltage by multiplying each of said first plurality of input values by a corresponding one of a set of coefficients that statistically relate said first plurality of input values to said second time value, and summing the multiplied values to produce a resulting time at which said output voltage reaches said different predetermined fraction of said supply voltage. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification