Power transmission lines: A new interconnect design to eliminate simultaneous switching noise

A major bottleneck in high-speed signaling is the simultaneous switching noise (SSN), which is caused by simultaneously switching output buffers. SSN is a result of the coupling between the signal lines and the power delivery network (PDN) in off-chip signaling. This coupling occurs at discontinuities of the transmission line, wherever there is an interruption of the current return path. A particular location where there is a return path discontinuity is the output buffer that is connected to a transmission line. To reduce this discontinuity, current designs try to maintain a low-impedance PDN for the I/O lines up to the output buffers on the chip. This requires a complicated design of the package and interconnections using, for example, planes for the PDN and decoupling capacitors on the package. For GHz signaling, it can be very difficult to maintain sufficiently low impedance. This paper presents a new PDN design, called as the power transmission line, which overcomes these problems.