Complementary network reduction for load modeling
First Claim
1. A method for providing a signal transition delay model for a circuit being designed, said method including the steps of:
- translating passive transistors to an RC circuit model comprising only resistors and capacitors;
reducing said RC circuit model to a "pi" model circuit, the "pi" model circuit having a first capacitor and a second capacitor; and
determining an effective capacitance value from said "pi" model circuit, said effective capacitance being representative of an effective impedance for a portion of said circuit being designed;
wherein said effective capacitance is a function of the first capacitor and the second capacitor of the "pi" model circuit and transition delay.
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Accused Products
Abstract
A process and implementing computer system (13) for optimally sizing elements of an integrated circuit includes determining actual arrival times and required arrival times (403) for processed signals at all nodes within the integrated circuit and determining the slack or difference (405) between arrival and required times for each node. If the actual arrival time for a particular node is after the time required to meet a predetermined design constraint of the node (407), a determination (411) is made regarding the effect of that element on the nodal slack for an incremental increase in the size of that element. Thereafter an element is selected (413) for sizing increase (415) in accordance with a weighting function and the process is repeated until all of the nodes in the integrated circuit have positive slack times (407, 409). One method of accomplishing a timing analysis step (303) includes an analytical circuit simulation technique (1000-1015) in which circuit "I-V" characteristics are more precisely represented with a power series (1006) including a plurality of regional segmental approximations (901-907). Another method of timing analysis includes an equivalency methodology (1501-1513) of translating passive transistors to equivalent RC networks (801). In the overall optimization process, a method is provided (1701-1715) for automatically correcting transistor predicted sensitivities based upon a correction factor (1713). A multi-model timing method (1601-1619) is also illustrated (1601-1619) for synergistically combining fast and accurate circuit timing models to optimize the speed and accuracy of the design process itself while remaining within an accuracy threshold.
47 Citations
14 Claims
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1. A method for providing a signal transition delay model for a circuit being designed, said method including the steps of:
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translating passive transistors to an RC circuit model comprising only resistors and capacitors; reducing said RC circuit model to a "pi" model circuit, the "pi" model circuit having a first capacitor and a second capacitor; and determining an effective capacitance value from said "pi" model circuit, said effective capacitance being representative of an effective impedance for a portion of said circuit being designed;
wherein said effective capacitance is a function of the first capacitor and the second capacitor of the "pi" model circuit and transition delay. - View Dependent Claims (2, 3, 4, 5)
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6. A storage medium which is selectively coupled to a processing circuit, said processing circuit including a medium reading device selectively operable to read said storage medium and provide program signals representative of indicia present on said storage media to the processing circuit, said storage medium being selectively operable in combination with said processing circuit for providing a simulated delay model for a circuit being designed, said method comprising:
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translating passive transistors to an RC circuit model comprising only resistors and capacitors; reducing said RC circuit model to a "pi" model circuit, the "pi" model circuit having a first capacitor and a second capacitor; and determining an effective capacitance value from said "pi" model circuit, said effective capacitance being representative of an effective impedance for a portion of said circuit being designed, wherein said effective capacitance is a function of the first capacitor and the second capacitor of the "pi" model circuit and transition delay. - View Dependent Claims (7, 8)
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9. A method for optimizing characteristics of a circuit being designed, said method comprising the steps of:
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determining a required time at which a propagated input signal must arrive at predetermined nodes of a plurality of elements within the circuit, in order to enable the circuit to provide an output signal at a specified output time, said required time being measured from a predetermined input start time; determining corresponding arrival times measured from said predetermined input start time, said corresponding arrival times being representative of times which said propagated input signal actually arrives at said predetermined nodes; calculating a slack time at each of said predetermined nodes, said slack time being representative of a time difference between the arrival time and the required time; selecting an element in accordance with a predetermined weighting function with regard to said slack times; and changing a characteristic of said selected element; wherein said step of determining corresponding arrival times further includes a delay model method for providing a simulated delay model for said circuit being designed, said delay model method comprising; translating passive transistors to an RC circuit model comprising only resistors and capacitors; reducing said RC circuit model to a "pi" model circuit, the "pi" model circuit having a first capacitor and a second capacitor; and determining an effective capacitance value from said "pi" model circuit, said effective capacitance being representative of an effective impedance for a portion of said circuit being designed, wherein said effective capacitance is a function of the first capacitor and the second capacitor of the "pi" model circuit and transition delay. - View Dependent Claims (10, 11)
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12. A storage medium which is selectively coupled to a processing circuit, said processing circuit including a medium reading device selectively operable to read said storage medium and provide program signals representative of indicia present on said storage media to processing circuit, said storage medium being selectively operable in combination with said processing circuit for optimizing characteristics of a circuit being designed, by accomplishing the steps of:
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determining a required time at which a propagated input signal must arrive at predetermined nodes of a plurality of elements within the circuit being designed, in order to enable the circuit being designed to provide an output signal at a specified output time, said required time being measured from a predetermined input start time; determining corresponding arrival times measured from said predetermined input start time, said corresponding arrival times being representative of times which said propagated input signal actually arrives at said predetermined nodes; calculating a slack time at each of said predetermined nodes, said slack time being representative of a time difference between the arrival time and the required time; selecting an element in accordance with a predetermined weighting function with regard to said slack times; and changing a size characteristic said selected element; wherein said step of determining corresponding arrival times further includes a delay model method for providing a simulated delay model for said circuit being designed, said delay model method comprising; translating passive transistors to an RC circuit model comprising only resistors and capacitors; reducing said RC circuit model to a "pi" model circuit, the "pi" model circuit having a first capacitor and a second capacitor; and determining an effective capacitance value from said "pi" model circuit, said effective capacitance being representative of an effective impedance for a portion of said circuit being designed, wherein said effective capacitance is a function of the first capacitor and the second capacitor of the "pi" model circuit and transition delay. - View Dependent Claims (13, 14)
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Specification