Area, Power, and Pin Efficient Bus Structures Using Multi-Bit-Differential Signaling

This paper describes a new low-power, area-, and pin-efficient alternative to differential encoding for high-performance chip-to-chip and backplane signaling. The technique, called multi-bit-differential-signaling (MBDS), consists of a new design for the driver and link termination network coupled with a novel coding system based on “N choose M (nCm)” codes. In an nCm-coded MBDS channel, there are n physical interconnections over which all code symbols carry exactly m 1-bits. This property gives MBDS links signal-to-noise and transmission characteristics comparable to pairwise differential links such as low-voltage differential signaling (LVDS). Moreover, MBDS is compatible with commercial LVDS receivers in point-to-point and multi-point bus topologies. However, because MBDS channels have a higher information density, they use up to 45% less power and up to 45% fewer I/O pads than equivalent differentially encoded buses.