Circuits, systems, and methods for reducing effects of cross talk in I/O lines and wire bonds
Circuits, architectures, a system and methods for reducing the effect(s) of cross talk in neighboring I/O signal paths. The circuitry generally includes first and second input/output (I/O) pads having first and second I/O signal lines coupled thereto, and a capacitor having first and second terminals coupled to the first I/O pad and/or signal line and the second I/O pad and/or signal line, respectively. The method generally comprises the steps of (1) transmitting or receiving a signal along a first I/O signal line in an integrated circuit, the first I/O signal line communicating with a first I/O pad on the integrated circuit, and the integrated circuit having a second I/O signal line communicating with a second I/O pad; and (2) capacitively coupling the first signal to the second I/O pad and/or the second I/O signal line, sufficiently to reduce the effect(s) of cross talk in the second I/O signal line. The present invention can significantly reduce the effects of cross talk in neighboring I/O signal paths, for both input and output signals.
1. An integrated circuit, comprising:
a first input/output (I/O) pad having a first single ended I/O signal line coupled thereto;
a second input/output (I/O) pad having a second single ended I/O signal line coupled thereto;
a first capacitor having (i) a first terminal coupled to said first I/O pad and/or said first single ended I/O signal line, (ii) a second terminal coupled to said second I/O pad and/or said second single ended I/O signal line, and (iii) a capacitance sufficient to reduce effects of cross talk between said first and second single ended I/O signal lines; and
an I/O block including the first I/O pad, an input buffer configured to receive input signals transmitted to the first I/O pad, and an output buffer configured to place the output buffer in a high-impedance state when the I/O block receives one of the input signals.
2. The integrated circuit of claim 1 , wherein said first and second single ended I/O signal lines respectively comprise first and second wire bonds to an integrated circuit package substrate.
3. The integrated circuit of claim 1 , wherein said first capacitor has a capacitance sufficient to minimize or substantially cancel said cross talk in said second single ended I/O signal line.
4. The integrated circuit of claim 1 , wherein said cross talk manifests itself as voltage noise and/or timing jitter.
5. The integrated circuit of claim 1 , wherein said first capacitor has a capacitance of from about 1 pF to about 3 pF.
6. The integrated circuit of claim 1 , wherein said first capacitor comprises first and second metal structures in a single layer of metal.
7. The integrated circuit of claim 6 , wherein each of said first and second metal structures comprises a plurality of interleaved fingers, each connected at one end to a perpendicular backbone.
8. The integrated circuit of claim 1 , wherein said first capacitor comprises first and second metal plates in adjacent layers of metal.
9. The integrated circuit of claim 1 , further comprising: (1) a third input/output (I/O) pad having a third single ended I/O signal line coupled thereto; and (2) a second capacitor having (i) a first terminal coupled to said second I/O pad and/or said second single ended I/O signal line, (ii) a second terminal coupled to said third I/O pad and/or said third single ended I/O signal line, and (iii) a capacitance sufficient to reduce effects of cross talk between said second and single ended third I/O signal lines.
10. The integrated circuit of claim 9 , wherein said third single ended I/O signal line comprises a third wire bond to said integrated circuit package substrate.
11. The integrated circuit of claim 9 , further comprising a third capacitor configured to reduce, minimize or substantially cancel effects of cross talk between said first single ended I/O signal line and said third single ended I/O signal line.
12. The integrated circuit of claim 1 , wherein said first and second I/O pads and said first capacitor are on a single die.
13. A method of reducing cross talk in an input/output (I/O) signal line, comprising the steps of:
transmitting or receiving a first signal along a first single ended I/O signal line in an integrated circuit, said first single ended I/O signal line communicating with a first I/O pad on said integrated circuit, and said integrated circuit having a second single ended I/O signal line communicating with a second I/O pad;
capacitively coupling said first signal to said second I/O pad and/or said second single ended I/O signal line, sufficiently to reduce effects of cross talk in said second single ended I/O signal line;
receiving input signals transmitted to the first I/O pad by an input buffer included in an I/O block having an output buffer; and
placing the output buffer in a high-impedance state when the I/O block receives one of the input signals.
14. The method of claim 13 , wherein said first and second single ended I/O signal lines respectively comprise first and second wire bonds to an integrated circuit package substrate.
15. The method of claim 13 , wherein said cross talk manifests itself as voltage noise and/or timing jitter.
16. The method of claim 13 , wherein said integrated circuit further comprises a first capacitor having (i) a first terminal coupled to said first I/O pad and/or said first single ended I/O signal line, (ii) a second terminal coupled to said second I/O pad and/or said second single ended I/O signal line and (iii) a capacitance sufficient to reduce said effects of cross talk between said first and second single ended I/O signal lines.
17. The method of claim 16 , wherein said first capacitor has a capacitance sufficient to minimize or substantially cancel said effects of cross talk between said first and second single ended I/O signal lines.
18. The method of claim 16 , wherein said first capacitor has a capacitance of from about 1 pF to about 3 pF.
19. The method of claim 16 , wherein said first capacitor comprises first and second metal structures in a single layer of metal.
20. The method of claim 19 , wherein each of said first and second metal structures comprises a plurality of interleaved fingers, each connected at one end to a perpendicular backbone.
21. The method of claim 16 , wherein said first capacitor comprises first and second metal plates in adjacent layers of metal.
22. The method of claim 13 , wherein said integrated circuit further comprises (1) a third input/output (I/O) pad having a third single ended I/O signal line coupled thereto, and (2) a second capacitor having (i) a first terminal coupled to said first I/O pad and/or said first single ended I/O signal line, and (ii) a second terminal coupled to said third I/O pad and/or said third single ended I/O signal line; and said method further comprises capacitively coupling said first signal to said third I/O pad and/or said third single ended I/O signal line sufficiently to reduce effects of cross talk in said third single ended I/O signal line.
23. The method of claim 22 , wherein said third single ended I/O signal line comprises a third wire bond to said integrated circuit package substrate.
24. The method of claim 22 , wherein said method further comprises:
transmitting or receiving a second signal on one of said second and third single ended I/O signal lines, and
capacitively coupling said second signal to the other of said second or third I/O pad and/or single ended I/O signal line, sufficiently to reduce said effects of cross talk in said other single ended I/O signal line.
25. The method of claim 24 , wherein said integrated circuit further comprises a third capacitor having (i) a first terminal coupled to said second I/O pad and/or said second single ended I/O signal line, (ii) a second terminal coupled to said third I/O pad and/or said third single ended I/O signal line, and (iii) a capacitance sufficient to reduce said effects of cross talk between said second and third single ended I/O signal lines.
26. The method of claim 16 , wherein said first and second I/O pads and said first capacitor are on a single die.