Optimization of library slew ratio based circuit
Disclosed is a technique for providing minimal sequential overhead in a flip-flop circuit. Equalization of setup times is achieved in one embodiment. In addition, delays in clock to Q can be equalized for both rising data transitions and falling data transitions. Large setup times are not required since optimization techniques equalize setup times for both rising and falling data transitions.
1. A method of reducing sequential overhead in a latching circuit design by adjusting rising and falling data setup times and clock to Q delays of rising and falling data transitions in a computer, wherein said computer performs the processes comprising:
creating an initial latching circuit design in said computer using a device library;
using library test cells of said device library in said computer to determine slew rates for combinational logic in said initial latching circuit;
using said slew rates for said combinational logic of said initial latching circuit to determine said rising and falling data setup times and clock to Q delays of said rising and falling data transitions in said computer;
altering device widths of said combinational logic of said initial latching circuit design in said computer to alter said slew rates so that said rising and falling data setup times are substantially equal, said clock to Q delays are substantially equal for said rising and falling data transitions, and said clock to Q delays are not increased by more than approximately ten percent, to generate a latching circuit design in said computer that is substantially polarity independent and has reduced sequential overhead.
2. The method of claim 1 wherein said process of altering device widths further comprises:
using hspice optimization routines to set concurrent goals for data setup times for both rising and falling data signals, and clock to Q delays for said rising and falling transitions.
3. The method of claim 2 wherein said process of altering said device widths further comprises:
using representative slew rates during hspice optimization for rising and falling data input transitions that are stored in said device library.
4. The method of claim 3 wherein said process of altering said device widths of said combinational logic of said initial circuit design comprises:
altering device widths of said combinational logic of said initial circuit design except for input and output inverters.