Current Mode On-Chip Interconnect using Level-Encoded Two-Phase Dual-Rail Encoding

We present delay variations insensitive long on-chip interconnect implementation based on current mode signaling and level-encoded two-phase dual-rail (LEDR) encoding. LEDR encoding is chosen over the normal two-phase dual-rail encoding because its completion detection and decoding circuitry is faster and much simpler since detection is level based rather than transition. The communication latency of this interconnect at global lengths of the wires reduces by half compared to conventional voltage mode LEDR interconnect. This is due to current mode signaling, making it possible to achieve high speed without pipelining and/or using repeaters. Performance simulation shows that at 5 mm wire length the throughput of this interconnect is 1 Gbps per one dual-rail wire pair. The effect of crosstalk on signal propagation delay is analyzed using four-bit parallel data transfer with the worst-case switching pattern and transmission line model which have both capacitive and inductive coupling. The interconnect circuitry is designed and simulated using Cadence Analog Spectre and Hspice with 130 nm CMOS technology.