Clock distribution network wiring structure
View Patent ↗A wiring structure for clock signals has two or more parallel clock signal wires disposed in adjacent power wire bays that span the distance between the sinks to which the clock signal wires are to be coupled. The parallel clock signal wires are shorted one to another by stubs placed at locations in order to time the clock wiring structure. The delay tuning of the structure is obtained by the discrete movement of wiring stubs between the wiring bays of the pre-defined power grid.
1. A clock signal distribution system for distributing high frequency clock signals to a plurality of physically separate sinks on a semiconductor chip, comprising in combination:
a pair of clock signal tracks extending along parallel paths and joined together at each end;
a clock signal source coupled to said clock signal tracks at a point intermediate said each end;
one clock signal track coupling said clock signal tracks to one of said physically separated sinks;
another clock signal track coupling said clock signal tracks to another of said physically separated sinks; and
a tuning stub connected across said pair of clock signal tracks located at a point between said source and said one of said physically separated sinks selected to reduce clock timing skew between said one of said physically separated sinks and said another of said physically separated sinks.
2. A clock signal distribution system as in claim 1 further including a tuning stub connected across said pair of clock signal tracks located at a point between said source and said another of said physically separated sinks selected to reduce clock timing skew between said one of said physically separated sinks and said another of said physically separated sinks.
3. A clock signal distribution system as in claim 1 wherein said semiconductor chip includes parallel power conducting tracks extending to said plurality of physically separated sinks, and said pair of clock signal tracks is disposed adjacent said power conducting tracks.
4. A clock signal distribution system as in claim 2 wherein said semiconductor chip includes parallel power conducting tracks extending to said plurality of physically separated sinks, and said pair of clock signal tracks is disposed adjacent said power conducting tracks.
5. A clock signal distribution system as in claim 1 wherein said point between said source and said one of said physically separated sinks is determined by an iterative simulation process.
6. A clock signal distribution system as in claim 2 wherein said point between said source and said another of said physically separated sinks is determined by an iterative simulation process.
7. A clock signal distribution system as in claim 4 wherein said point between said source and said one of said physically separated sinks is determined by an iterative simulation process.
8. A clock signal distribution system as in claim 3 wherein said point between said source and said one of said physically separated sinks is determined by an iterative simulation process.
9. A clock signal distribution system as in claim 4 wherein said point between said source and said one of said physically separated sinks is determined by an iterative simulation process.
10. A clock signal distribution system as in claim 5 wherein said point between said source and said another of said physically separated sinks is determined by an iterative simulation process.
11. A clock signal distribution system as in claim 5 wherein said iterative simulation process moves said stub in increments equal to the power grid pitch.
12. A clock signal distribution system as in claim 6 wherein said iterative simulation process moves said stub in increments equal to the power grid pitch.
13. A clock signal distribution system as in claim 7 wherein said iterative simulation process moves said stub in increments equal to the power grid pitch.
14. A method for designing a clock signal distribution system from a global clock source to a plurality of physically separated sinks, including the steps of:
selecting a wiring structure, said wiring structure having one or more tuning stubs, each of which is connected across a pair of clock signal tracks at a point between said source and one of said physically separated sinks;
simulating, by using a computer, the selected wiring structure to determine waveform slew at said plurality of physically separated sinks;
changing the selected wiring structure to bring the waveform slew within specified limits; and
moving at least one of said one or more stubs of the wiring structure to match the delay on all sinks.
15. A method for designing a clock distribution system as in claim 14 wherein said moving step includes working with two sinks at a time starting with simulating two sinks that give the maximum clock skew.
16. A method for designing a clock distribution system as in claim 14 wherein in said moving step simulation said stubs are moved in predetermined increments.
17. A method for designing a clock distribution system as in claim 15 wherein in said moving step simulation said stubs are moved in predetermined increments.
18. A method for designing a clock distribution system as in claim 16 wherein one predetermined increment is equal to the power grid pitch.
19. A method for designing a clock distribution system as in claim 17 wherein one predetermined increment is equal to the power grid pitch.