A 2.8 mW/Gb/s, 14 Gb/s Serial Link Transceiver

Abstract

Design techniques to improve energy efficiency of serial link transceivers are presented. Power consumption is reduced by using: 1) low-power clock generation, recovery, and distribution schemes; 2) charge-based circuits to implement analog front-end and samplers/flip-flops; and 3) a partially segmented voltage-mode (VM) output driver. An LC-oscillator based digital phase-locked loop (PLL) is used to generate a low jitter clock that is shared between the transmitter (Tx) and receiver (Rx). The clock recovery unit uses a local ring-oscillator based PLL to reduce the number of phase interpolators and the amount of high-frequency clock distribution. Charge-based samplers that were shown to operate with limited return-to-zero voltage swings and consume only dynamic power are modified to provide non-return-to-zero outputs and used extensively in the deserializer and Rx front-end circuits. A partially segmented VM output driver with embedded 2-tap de-emphasis is proposed to reduce power consumption of pre-drivers. Fabricated in a 65 nm CMOS process, the 14 Gb/s transceiver prototype employs aforementioned techniques and achieves an energy efficiency of 2.8 mW/Gb/s. The Tx achieves a phase margin of 0.36 UI (BER = 10-12) at the end of an 11 dB loss channel with an energy efficiency of 0.89 mW/Gb/s. The Rx recovers clock with 1.8 psrms long term absolute jitter at BER < 10-12 and achieves an energy efficiency of 1.69 mW/Gb/s. The LC-oscillator based digital PLL achieves an integrated jitter of 0.605 psrms with an energy efficiency of 0.5 mW/GHz at 7 GHz output frequency.