System and Method for Approximating Intrinsic Capacitance of an IC Block

Abstract

A system, method, and computer program product for approximating intrinsic capacitance of an integrated circuit (IC) block such as, for example, a compilable memory instance. Estimates of N-well capacitance, metal grid capacitance, and non-switching circuitry capacitance associated with the IC block are obtained. A total intrinsic capacitance of the IC block is then estimated based on the aforesaid constituent estimates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure may be had by reference to the following Detailed Description when taken in conjunction with the accompanying drawings wherein:

FIG. 1 depicts a high-level circuit abstraction scheme involving an IC block where intrinsic capacitance may be approximated according to one or more embodiments of the present disclosure;

FIG. 2 is a flowchart of a method of approximating intrinsic capacitance of an IC block in one embodiment;

FIG. 3 depicts an exemplary CMOS model for illustrating N-well capacitance of an IC block;

FIG. 4 depicts a flowchart of a method of estimating N-well capacitance of an IC block in one embodiment;

FIGS. 5A and 5B depict exemplary CMOS models for illustrating non-switching circuitry capacitance of an IC block;

FIG. 6 depicts a flowchart of a method of estimating non-switching circuitry capacitance of an IC block in one embodiment;

FIG. 7 depicts an exemplary IC block with different functional blocks; and

FIG. 8 illustrates a computer system operable to implement the method of approximating intrinsic capacitance in accordance with an embodiment of the present disclosure.

Claims

1. A method of approximating intrinsic capacitance of an integrated circuit (IC) block, comprising: estimating an N-well capacitance associated with said IC block to obtain an N-well capacitance estimate;estimating a metal grid capacitance associated with said IC block to obtain a metal grid capacitance estimate;estimating a non-switching circuitry capacitance associated with said IC block to obtain a non-switching circuitry capacitance estimate; andestimating a total intrinsic capacitance associated with said IC block based on said estimates of N-well capacitance, metal grid capacitance and non-switching circuitry capacitance.

2. The method of approximating intrinsic capacitance as set forth in claim 1, further comprising: dividing said IC block into a plurality of leaf cells that are categorized into groups;calculating, for each group, a leaf cell's N-well capacitance and extrapolating it with respect to the entire group; andobtaining said N-well capacitance estimate for said IC block by aggregating each group's N-well capacitance.

3. The method of approximating intrinsic capacitance as set forth in claim 2, further comprising ensuring that overlapping dimensions of at least two adjacent leaf cells are not counted multiple times in said extrapolating step.

4. The method of approximating intrinsic capacitance as set forth in claim 3, wherein said ensuring is effectuated by designating a particular leaf cell such that it does not share an N-well boundary with another leaf cell.

5. The method of approximating intrinsic capacitance as set forth in claim 1, wherein said metal grid capacitance estimate is obtained by measuring metal capacitance associated with active leaf cells of said IC block during at least one of a read operation and a write operation.

6. The method of approximating intrinsic capacitance as set forth in claim 1, further comprising: dividing said IC block into a plurality of leaf cells and initializing a leaf cell's inputs and latches;decrementing a voltage applied to said leaf cell by a predetermined amount in a predetermined time interval;measuring a change in electric charge applied to said IC block; andobtaining said non-switching circuitry capacitance estimate based on said change in electric charge and aggregating it over said IC block.

7. The method of approximating intrinsic capacitance as set forth in claim 6, further comprising subtracting a leakage component in obtaining said non-switching circuitry capacitance estimate.

8. The method of approximating intrinsic capacitance as set forth in claim 1, further comprising: determining if an internal decoupling capacitor is associated with said IC block;if so, estimating a capacitance value with respect to said internal decoupling capacitor; andaccounting for said capacitance value in estimating said total intrinsic capacitance associated with said IC block.

9. A computer-implemented system for approximating intrinsic capacitance of an integrated circuit (IC) block, comprising: means for estimating an N-well capacitance associated with said IC block to obtain an N-well capacitance estimate;means for estimating a metal grid capacitance associated with said IC block to obtain a metal grid capacitance estimate;means for estimating a non-switching circuitry capacitance associated with said IC block to obtain a non-switching circuitry capacitance estimate; andmeans for estimating a total intrinsic capacitance associated with said IC block based on said estimates of N-well capacitance, metal grid capacitance and non-switching circuitry capacitance.

10. The computer-implemented system for approximating intrinsic capacitance as set forth in claim 9, further comprising: means for dividing said IC block into a plurality of leaf cells that are categorized into groups;means for calculating, for each group, a leaf cell's N-well capacitance and for extrapolating it with respect to the entire group; andmeans for obtaining said N-well capacitance estimate for said IC block by aggregating each group's N-well capacitance.

11. The computer-implemented system for approximating intrinsic capacitance as set forth in claim 10, further comprising means for ensuring that overlapping dimensions of at least two adjacent leaf cells are not counted multiple times in said extrapolating step.

12. The computer-implemented system for approximating intrinsic capacitance as set forth in claim 11, wherein said ensuring is effectuated by designating a particular leaf cell such that it does not share an N-well boundary with another leaf cell.

13. The computer-implemented system for approximating intrinsic capacitance as set forth in claim 9, further comprising: means dividing said IC block into a plurality of leaf cells;means for initializing a leaf cell's inputs and latches;means for measuring a change in electric charge applied to said leaf cell in a predetermined time interval; andmeans for obtaining said non-switching circuitry capacitance estimate based on said change in electric charge and aggregating it over said IC block.

14. The computer-implemented system for approximating intrinsic capacitance as set forth in claim 9, further comprising means for estimating a capacitance value with respect to an internal decoupling capacitor associated with said IC block such that said capacitance value is accounted for in estimating said total intrinsic capacitance associated with said IC block.

15. The computer-implemented system for approximating intrinsic capacitance as set forth in claim 9, wherein said metal grid capacitance estimate is obtained by measuring metal capacitance associated with active leaf cells of said IC block during at least one of a read operation and a write operation.

16. A computer program product operable to be executed in association with a computer system, said computer program product having instructions for approximating intrinsic capacitance of an integrated circuit (IC) block, comprising: a code portion for estimating an N-well capacitance associated with said IC block to obtain an N-well capacitance estimate;a code portion for estimating a metal grid capacitance associated with said IC block to obtain a metal grid capacitance estimate;a code portion for estimating a non-switching circuitry capacitance associated with said IC block to obtain a non-switching circuitry capacitance estimate; anda code portion for estimating a total intrinsic capacitance associated with said IC block based on said estimates of N-well capacitance, metal grid capacitance and non-switching circuitry capacitance.

17. The computer program product as set forth in claim 16, further comprising: a code portion for dividing said IC block into a plurality of leaf cells that are categorized into groups;a code portion for calculating, for each group, a leaf cell's N-well capacitance and for extrapolating it with respect to the entire group; anda code portion for obtaining said N-well capacitance estimate for said IC block by aggregating each group's N-well capacitance.

18. The computer program product as set forth in claim 17, further comprising a code portion for ensuring that overlapping dimensions of at least two adjacent leaf cells are not counted multiple times in said extrapolating step.

19. The computer program product as set forth in claim 18, wherein said ensuring is effectuated by designating a particular leaf cell such that it does not share an N-well boundary with another leaf cell.

20. The computer program product as set forth in claim 14, further comprising: a code portion for dividing said IC block into a plurality of leaf cells;a code portion for initializing a leaf cell's inputs and latches;a code portion for decrementing a voltage applied to said leaf cell by a predetermined amount in a predetermined time interval;a code portion for measuring a change in electric charge applied to said leaf cell; anda code portion for obtaining said non-switching circuitry capacitance estimate based on said change in electric charge and aggregating it over said IC block.

21. The computer program product as set forth in claim 16, further comprising a code portion for estimating a capacitance value with respect to an internal decoupling capacitor associated with said IC block such that said capacitance value is accounted for in estimating said total intrinsic capacitance associated with said IC block.

22. The computer program product as set forth in claim 16, wherein said metal grid capacitance estimate is obtained by measuring metal capacitance associated with active leaf cells of said IC block during at least one of a read operation and a write operation.