A 5 Gb/s Energy-Ef ficient V oltage-Mode Transmitter Using Time-Based De-Emphasis Saurabh Saxena, Student Member , IEEE, Romesh Kumar Nandwana , Student Member , IEEE,a n d Pavan

Abstract

In this paper, we present a time-based equalization scheme to implement transmit de-emphasis in voltage-mode drivers. Using two-level pulse-width modulation, this work de- couples the tradeoff between imp edance matching, output swing, and de-emphasis resolution in co nventional voltage-mode drivers using voltage-based de-emphasi s. A prototype PWM-based 5 Gb/s voltage-mode transmitter was implemented in a 90 nm CMOS process and characterized acros s different channels and output swings. The horizontal/vertical eye opening at the end of 60 and 96 in stripline channels is 78 mv/0.6 UI and 8 mV/0.3 UI, respectively. Duty cycle distortion of the clock severely reduced the margins, so the overa ll performance can be improved by applying duty-cycle correction to clock signals. The transmitter consumes a total power 15.6 mW of which 2.5 mW is consumed in the digital PLL and 7.8 mW in the pre-/output drivers and regulators. This translates to a power ef ficiency of 3.1 mW/Gb/s, which compares favorably with the state of the art.