Phase and Amplitude Pre-Emphasis Techniques for Low-Power Serial Links

J. Buckwalter, M. Meghelli, D. J. Friedman, and A. Hajimiri

A novel approach to equalization of high-speed serial links combines both amplitude pre-emphasis to correct for intersymbol interference and phase pre-emphasis to compensate for deterministic jitter, in particular, data-dependent jitter. Phase preemphasis augments the performance of low power transmitters in bandwidth-limited channels. The transmitter circuit is implemented in a 90-nm bulk CMOS process and reduces power consumption by pushing CMOS static logic to the output stage, a 4:1 output multiplexer. The received signal jitter over a cable is reduced from 16.15 ps to 10.29 ps with only phase pre-emphasis at the transmitter. The jitter is reduced by 3.6 ps over an FR-4 backplane interconnect. A transmitter without phase pre-emphasis consumes 18 mW of power at 6 Gb/s and 600 mVpp output swing, a power budget of 3 mW/Gb/s, while a transmitter with phase pre-emphasis consumes 24 mW, a budget of 4 mW/Gb/s.