Optimization of circuit designs using a continuous spectrum of library cells

A method of optimizing a circuit design having a plurality of cells, comprising the steps of:

• (a) providing at least one set of cells, each set including a plurality of logically equivalent cells, including at least one real cell and virtual cells, that vary in a design parameter, and each plurality of logically equivalent cells having a relatively continuous spectrum of values of the design parameter, wherein said virtual cells include timing characteristics derived from said at least one real cell;
• (b) evaluating a timing characteristic of the circuit design;
• (c) selecting a worst case timing path in the circuit design;
• and
• (d) replacing a cell in the selected timing path with a cell provided in said step (a).

A method of optimizing a circuit design having a plurality of cells, comprising the steps of:

• (a) providing at least one set of cells, each set including a plurality of logically equivalent cells, including at least one real cell and virtual cells, that vary in a design parameter, and each plurality of logically equivalent cells having a relatively continuous spectrum of values of the design parameter, wherein said virtual cells include timing characteristics derived from said at least one real cell;
• (b) evaluating a timing characteristic of the circuit design;
• (c) selecting a worst case timing path in the circuit design;
• (d) replacing a cell in the selected timing path with a cell provided in said step (a) having an incremental increase in drive strength;
• (e) evaluating the delay of the selected timing path after said step (d);
• (f) determining whether to retain the replacement made in said step (d);
• (g) repeating said steps (d), (e) and (f) until a first condition is met;
• (h) replacing a cell in the selected timing path with a cell provided in said step (a);
• (i) evaluating the delay of the selected timing path after said step (h);
• (j) determining whether to retain the replacement made in said step (h);
• and
• (k) repeating said steps (h), (i) and (j) until a second condition is met.

A method of creating a virtual library, comprising the steps of:

• (a) providing a real library including timing characteristics of one or more cells;
• (b) providing a virtual library by computing timing characteristics of a plurality of virtual cells that are logically equivalent to a cell in the real library, wherein said timing characteristics of said virtual cells are derived from said timing characteristics in said real library;
• and
• wherein said real library and said virtual library comprise a plurality of logically equivalent cells that vary in a design parameter, said plurality of logically equivalent cells having a relatively continuous spectrum of values of said design parameter.