A Supply-Scalable Serializing Transmitter with Controllable Output Swing and Equalization for Next Generation Standards

Abstract

Supporting a wide operating range for industrial-standard backward-compatible transmitters often results in energy inefficiency. This paper describes an energy-efficient voltage-mode-serializing transmitter with an operating range of up to 32 Gb/s. The proposed transmitter uses a programmable internal supply to set the voltage level for various data rates optimally, thus improving overall energy efficiency. Output swing and pre-emphasis levels are largely adjustable while the constant output impedance is maintained using a dedicated control loop. CMOS-logic-based circuits and quarter-rate clocking enhance the energy efficiency over the entire data rate range, while a P-over-N voltage-mode driver is used to achieve a high maximum output swing. Two supply regulators with replicas provide constant pull-up and pull-down impedances of the output driver. The variable output swing, pre-emphasis, and internal supply are realized by using segmented output drivers and replicas. The proposed transmitter, fabricated in a 65-nm CMOS process, occupies an active area of 0.173 mm2. The prototype chip achieves a wide output swing range of 0.4–1.3 Vppd and an energy efficiency of 2.10–3.45 pJ/bit, across a data rate of 5 –32 Gb/s.