AC Coupled Interconnect

Dr. Paul D. Franzon

paulf@ncsu.edu

919.515.7351, fax. 919.515.2285
www.ece.ncsu.edu/erl/faculty/paulf.html

Brief Description

The central thesis in this effort hinges on the recognition that the DC component of a digital signal carries no information, and that non-contacting AC connections can be built a lot denser and simpler than DC connections.  An array of non-contacting structures is inherently denser, more compliant and more mechanically robust than an array of contacting structures.   As shown in the Figures below, these non-contacting structures can be built as capacitor half-plates or opposing inductor spirals of a transformer.  In the capacitive case, the signal is carried through a series capacitor.  In the transformer case, by a small signal transformer.  By imposing direct contacts only where DC signal transfers are needed, this approach will allow very high density interconnects to be realized and alleviate the compliance and rework problems encountered in other high density interconnect technologies. The main goals of this project are as follows:

• Demonstration of ultra-low power I/O techniques using series capacitors and other novel interconnect circuits (< 2 mW/Gbps)
• Demonstration of possible fiber channel replacement technology that reduces cost and parasitics
• Demonstration of capacitive coupled connections for chip-substrate packaging at a 75 um I/O pitch.
• Demonstration of inductive coupled connections for connector and socket structures at 250 um pitch.
• Demonstration of the acpplication of AC Coupled interconnect in 3D die stacking.

These demonstrations will show interconnect structure capable of supporting signaling up to 20 Gbps, at low power consumptions, and Bit Error Rates (BER) better than 10-12.

We gratefully acknowledge the support of AFRL, DARPA, NSF and SRC in this work.

Selected Publications

· K. Chandrashekar, J. Wilson, E. Erickson, Z. Feng, J. Xu, S. Mick, and P. Franzon, "Inductively Coupled Connectors and Sockets for Multi-Gbps Pulse Signaling," IEEE TADVP, VOl. 31, No. 4, Nov. 2008, pp. 748-758.   Paper

• B. Su, P. Patel, S.W. Hunter, M. Cases, and P.D. Franzon, "AC Coupled Backplane Using Embedded Capacitor," in Proc. IEEE EPEP, 27-29 Oct., 2008, pp. 295-298. Paper

• L. Luo, J.M. Wilson, S.E. Mick, J. Xu, L. Zhang, P.D Franzon, “3 Gb/s AC coupled chip-to-chip communication using a low swing pulse receiver,” IEEE JSSC, Vol. 41, No. 1, Jan 2006, pp. 287-296. Paper

· L. Luo, J. Wilson, S. Mick, J. Xu, L. Zhang, E. Erickson, P. Franzon, "A 36Gb/s ACCI Multi-Channel Bus using a Fully Differential Pulse Receiver", in Proceedings of the IEEE,Custom Integrated Circuits Conference, 2006, Sept. 2006, pp.773-776. Paper

· K. Chandrasekar, J. Wilson, E. Erickson, Z. Feng, J. Xu, S. Mick, P. Franzon, “Fine pitch inductively coupled connectors for multi-Gbps pulse signaling,” in Proc. IEEE Electrical Performance of Electronic Packaging, Oct. 2006, pp. 11-14. Paper

· J. Wilson, L. Luo, S. Mick, B. Chan, H. Lin, P. Franzon, “AC Coupled Interconnect using Buried Bumps for Laminated Organic Packages”, in Proc. Electronic Components and Technology, ECTC, May/June, 2006. Paper Presentation

· L. Luo, J. Wilson, J. Xu, S. Mick, P. Franzon, “Signal integrity and robustness of ACCI packaged systems,“ in Proc. IEEE EPEP, Oct. 2005, pp. 11-14. Paper

· L. Luo, J. M. Wilson, S.E. Mick, J. Xu, L. Zhang, and P.D. Franzon, “A 3 Gb/s AC Coupled Chip-to-Chip Communication,” 2005 International Solid State Circuits Conference, San Francisco, Feb. 2005. paper presentation

· J. Xu, L. Luo, S. Mick, J. Wilson, P. Franzon, “AC Coupled Interconnect for Dense 3-D ICs, “AC Coupled Interconnect for Dense 3-D ICs,” in IEEE Transactions on Nuclear Science (TNS). Vol. 51(5), Oct, 2004, pp. 2156-2160. Paper

· J. Wilson, S. Mick, J. Xu,S. Bonafede, A. Huffman, R. LaBennett, and P.D. Franzon, “Fully Integrated AC Coupled Interconnect Using Buried Bumps,” in IEEE Adv. Pack., 30(2), May 2007, pp. 191-199. Paper

· S. Mick, L. Luo, J. Wilson, P. Franzon, “Buried Bump and AC Coupled Interconnection Technology, IEEE Trans. Adv.Packaging, 27(1), Feb, 2004, pp. 121-125. Paper

• S. E. Mick, J. M. Wilson, and P. Franzon, “4 Gbps AC Coupled Interconnection,” , IEEE Custom Integrated Circuits Conference, May 12-16, 2002, pp. 133-140.
• S. Mick, P. Franozn, A. Huffman, Packaging Technology for AC Coupled Interconnection, IEEE Flip-Chip Conference, July 2002. Paper

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