Computing current in a digital circuit based on an accurate current model for library cells

• US 7,313,771 B2
• Filed: 03/31/2005
• Issued: 12/25/2007
• Est. Priority Date: 03/31/2005
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Reddy, Subodh M., Murgai, Rajeev
• Primary Examiner(s): Whitmore, Stacy
• Application Number:
  US11/096,138
• Publication Number:
  US 20060225009A1
• Time in Patent Office: 999 Days
• Field of Search: 716/1, 716/4, 703 13- 14
• US Class Current: 716/136
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods

Abstract

In one embodiment, a method for computing current in a digital circuit based on an accurate current model for library cells includes accessing a cell library, for each cell in the cell library corresponding to a cell in a digital circuit, generating multiple waveforms of current drawn by the cell from a power supply according to one or more predetermined values of one or more input parameters of the cell, analyzing the digital circuit to determine one or more actual values of the input parameters of each cell in the digital circuit, for each of the cells in the digital circuit, generating a current waveform according to the determined actual values of the input parameters and a waveform of current drawn by the cell from the power supply generated by the characterization module corresponding to the determined actual values of the input parameters, and summing the current waveforms of the cells in the digital circuit to generate a waveform of current drawn by the digital circuit from the power supply for use in a pattern-dependent methodology (PDM) or a patten-independent methodology (PIM).

Claims

1. A system for computing current in a digital circuit based on an accurate current model for library cells, the system comprising:

a characterization module operable to;

access a cell library;

for each cell in the cell library corresponding to a cell in a digital circuit, generate a plurality of waveforms of current drawn by the cell from a power supply according to one or more predetermined values of one or more input parameters of the cell; and

a current waveform generator operable to;

analyze the digital circuit to determine one or more actual values of the input parameters of each cell in the digital circuit;

for each of the cells in the digital circuit, generate a current waveform according to the determined actual values of the input parameters and a waveform of current drawn by the cell from the power supply generated by the characterization module corresponding to the determined actual values of the input parameters; and

sum the current waveforms of the cells in the digital circuit to generate a waveform of current drawn by the digital circuit from the power supply for use in a pattern-dependent methodology (PDM) or a pattern-independent methodology (PIM).

2. The system of claim 1, wherein the input parameters comprise input slew, input vector, output load, and input arrival time.

3. The system of claim 1, wherein the current waveform generator uses linear interpolation to generate one or more of the current waveforms of one or more of the cells in the digital circuit.

4. The system of claim 1, wherein the current waveform generator generates the waveform of current drawn by the digital circuit from the power supply for analysis of power consumption by the digital circuit.

5. The system of claim 4, wherein the analysis of power consumption by the digital circuit comprises use of a PDM.

6. The system of claim 4, wherein the analysis of power consumption by the digital circuit comprises use of a PIM.

7. The system of claim 1, wherein the current waveform generator generates the waveform of current drawn by the digital circuit from the power supply for analysis of noise in a substrate associated with the digital circuit.

8. The system of claim 7, wherein the substrate is associated with analog circuitry in addition to being associated with the digital circuit.

9. The system of claim 7, further comprising a reduced model (RM) generator operable to generate an RM of the digital circuit according to the waveform of current drawn by the digital circuit from the power supply for the analysis of noise in the substrate.

10. The system of claim 7, wherein the analysis of noise in the substrate comprises use of a PDM.

11. The system of claim 7, wherein the analysis of noise in the substrate comprises use of a PIM.

12. A method for computing current in a digital circuit based on an accurate current model for library cells, the method comprising:

accessing a cell library;

for each cell in the cell library corresponding to a cell in a digital circuit, generating a plurality of waveforms of current drawn by the cell from a power supply according to one or more predetermined values of one or more input parameters of the cell;

analyzing the digital circuit to determine one or more actual values of the input parameters of each cell in the digital circuit;

for each of the cells in the digital circuit, generating a current waveform according to the determined actual values of the input parameters and a waveform of current drawn by the cell from the power supply generated by the characterization module corresponding to the determined actual values of the input parameters; and

summing the current waveforms of the cells in the digital circuit to generate a waveform of current drawn by the digital circuit from the power supply for use in a pattern-dependent methodology (PDM) or a pattern-independent methodology (PIM).

13. The method of claim 12, wherein the input parameters comprise input slew, input vector, output load, and input arrival time.

14. The method of claim 12, wherein generating one or more of the current waveforms of one or more of the cells in the digital circuit comprises using linear interpolation.

15. The method of claim 12, further comprising using the waveform of current drawn by the digital circuit from the power supply for analysis of power consumption by the digital circuit.

16. The system of claim 15, wherein the analysis of power consumption by the digital circuit comprises use of a PDM.

17. The system of claim 15, wherein the analysis of power consumption by the digital circuit comprises use of a PIM.

18. The method of claim 12, further comprising using the waveform of current drawn by the digital circuit from the power supply for analysis of noise in a substrate associated with the digital circuit.

19. The method of claim 18, wherein the substrate is associated with analog circuitry in addition to being associated with the digital circuit.

20. The method of claim 18 further comprising generating a reduced model (RM) of the digital circuit according to the waveform of current drawn by the digital circuit from the power supply for the analysis of noise in the substrate.

21. The method of claim 18 wherein the analysis of noise in the substrate comprises use of a PDM.

22. The method of claim 18, wherein the analysis of noise in the substrate comprises use of a PIM.

23. Logic for computing current in a digital circuit based on an accurate current model for library cells, the logic encoded in one or more tangible media for execution and when executed operable to:

access a cell library;

for each cell in the cell library corresponding to a cell in a digital circuit, generate a plurality of waveforms of current drawn by the cell from a power supply according to one or more predetermined values of one or more input parameters of the cell;

analyze the digital circuit to determine one or more actual values of the input parameters of each cell in the digital circuit;

for each of the cells in the digital circuit, generate a current waveform according to the determined actual values of the input parameters and a waveform of current drawn by the cell from the power supply generated by the characterization module corresponding to the determined actual values of the input parameters; and

sum the current waveforms of the cells in the digital circuit to generate a waveform of current drawn by the digital circuit from the power supply for use in a pattern-dependent methodology (PDM) or a pattern-independent methodology (PIM).

24. The logic of claim 23, wherein the input parameters comprise input slew, input vector, output load, and input arrival time.

25. The logic of claim 23, operable to use linear interpolation to generate one or more of the current waveforms of one or more of the cells in the digital circuit.

26. The logic of claim 23, further operable to use the waveform of current drawn by the digital circuit from the power supply for analysis of power consumption by the digital circuit.

27. The system of claim 26, wherein the analysis of power consumption by the digital circuit comprises use of a PDM.

28. The system of claim 26, wherein the analysis of power consumption by the digital circuit comprises use of a PIM.

29. The logic of claim 23, further operable to use the waveform of current drawn by the digital circuit from the power supply for analysis of noise in a substrate associated with the digital circuit.

30. The logic of claim 29, wherein the substrate is associated with analog circuitry in addition to being associated with the digital circuit.

31. The logic of claim 29, further operable to generate a reduced model (RM) of the digital circuit according to the waveform of current drawn by the digital circuit from the power supply for the analysis of noise in the substrate.

32. The logic of claim 29, wherein the analysis of noise in the substrate comprises use of a PDM.

33. The logic of claim 29, wherein the analysis of noise in the substrate comprises use of a PIM.

34. A system for computing current in a digital circuit based on an accurate current model for library cells, the system comprising:

means for accessing a cell library;

means for, for each cell in the cell library corresponding to a cell in a digital circuit, generating a plurality of waveforms of current drawn by the cell from a power supply according to one or more predetermined values of one or more input parameters of the cell;

means for analyzing the digital circuit to determine one or more actual values of the input parameters of each cell in the digital circuit;

means for, for each of the cells in the digital circuit, generating a current waveform according to the determined actual values of the input parameters and a waveform of current drawn by the cell from the power supply generated by the characterization module corresponding to the determined actual values of the input parameters; and

means for summing the current waveforms of the cells in the digital circuit to generate a waveform of current drawn by the digital circuit from the power supply for use in a pattern-dependent methodology (PDM) or a pattern-independent methodology (PIM).