Power efficient chip-to-chip signaling schemes

In low voltage signaling for chip-to-chip digital communication, noise is a crucial factor and since common-mode noise is prevalent on matched printed circuit board (PCB) traces, differential signaling is an effective method for chip-to-chip communication. However, it needs two signal paths for transmitting one bit. Multi-level signaling can be used to reduce the number of required signal paths for transmitting one bit. To reduce the required signal power, this paper investigates several coding schemes for this application. A novel scheme, which improves the performance of ordinary 4-level pulse amplitude modulation (PAM) by roughly 3 dB, is proposed. Finally a low complexity method for an analog implementation of this scheme is presented.