System and method for calculating effective capacitance for timing analysis
View Patent ↗A method involves: accessing data representing an interconnect model, where the interconnect model includes a driving point node and is not a lumped capacitance model; calculating a value of an effective capacitance of the interconnect model to be inversely proportional to a voltage at the driving point node of the interconnect model; and storing the value of the effective capacitance. Such a method can be used to calculate effective capacitance of the interconnect model using analytical techniques.
1. A method, comprising:
accessing data representing an interconnect model, wherein the interconnect model includes a driving point node;
reducing the interconnect model to a lumped capacitance model consisting of an effective capacitance, wherein said reducing comprises:
calculating the effective capacitance by setting a voltage across the effective capacitance equal to a voltage at the driving point node of the interconnect model; and
storing a value representing the effective capacitance.
2. The method of claim 1 , wherein said calculating the effective capacitance comprises:
scaling one or more capacitances, included in the interconnect model, by a ratio of a voltage across the one or more capacitances to the voltage at the driving point node.
3. The method of claim 2 , wherein
the scaling the one or more capacitances comprises:
scaling a first capacitance included in the interconnect model by a ratio of a voltage across the first capacitance to the voltage at the driving point node, wherein
the scaling the first capacitance produces a first scaled capacitance;
scaling a second capacitance included in the interconnect model by a ratio of a voltage across the second capacitance to the voltage at the driving point node, wherein
the scaling the second capacitance produces a second scaled capacitance; and
the calculating the effective capacitance comprises:
summing the first scaled capacitance and the second scaled capacitance to produce an effective capacitance value.
4. The method of claim 3 , further comprising:
calculating a plurality of time constants from the first capacitance and the second capacitance; and
using the plurality of time constants to perform said scaling the first capacitance, said scaling the second capacitance, and said summing.
5. The method of claim 2 , wherein
the scaling the one or more capacitances comprises:
multiplying each one of the one or more capacitances by a respective voltage across that one of the one or more capacitances to generate a respective one of one or more first products; and
dividing each one of the one or more first products by the voltage at the driving point node to produce a respective one of one or more second products; and
the calculating the effective capacitance comprises summing the one or more second products to produce an effective capacitance value.
6. The method of claim 2 , wherein the scaling the one or more capacitances comprises:
multiplying each one of the one or more capacitances by a respective voltage across that one of the one or more capacitances to generate a respective one of one or more first products;
summing the one or more first products to produce a first value; and
dividing the first value by the voltage at the driving point node to produce an effective capacitance value.