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Hanumolu, Pavan Kumar Hanumolu, Pavan Kumar Shanbhag, Naresh R Schutt-Aine, Jose Viswanath, Pramod Saxena, Saurabh 2016-03-02T21:06:32Z 2016-03-02T21:06:32Z 2018-03-03T10:15:31Z 2015-11-18 2015-12 High performance computing and communication are two key aspects of all information processing systems. With aggressive scaling of silicon technology enabling integration of a large number of transistors in a small area, managing power and thermal reliability has become very challenging. While lowering the power needed for performing computation has been the prime focus for decades, energy consumed for data transfer has recently become a major bottleneck especially in high performance applications. The focus of this thesis is on improving energy efficiency of communication links by exploring design techniques at both the architectural and circuit levels. In the first part of this work, we propose a time-based equalization scheme to implement transmit de-emphasis in voltage-mode output drivers. Using two-level pulse-width modulation, it overcomes the tradeoff between impedance matching, output swing, and de-emphasis resolution in conventional voltage-mode drivers. A prototype PWM-based 5$\,$Gb/s voltage-mode transmitter was implemented in a 90$\,$nm CMOS process and characterized across different channels and output swings to demonstrate the effectiveness of proposed techniques. The horizontal/vertical eye openings (BER=$\rm 10^{-12}$) at the ends of 60$\,$inch and 96$\,$inch stripline channels are 78$\,$mV/0.6$\,$UI and 8$\,$mV/0.3$\,$UI, respectively. This transmitter achieves an energy efficiency of 3.1$\,$mW/Gb/s while compensating for 16-28$\,$dB channel loss, which compares favorably with the state-of-the-art. In the second part, techniques to improve energy efficiency of a complete transceiver are presented. The transmitter employs a novel partially segmented voltage-mode output driver to lower power consumption in pre-drivers during 2-tap FIR equalization. The receiver implements a low power half-rate clock and data recovery with the proposed ring PLL based multi-phase sampling clock generation in CDR loop and charge-based sampling and deserialization. These techniques are verified using the measured results obtained from a 14Gb/s transceiver prototype. Transmitter achieves an energy efficiency of 0.89$\,$mW/Gb/s while securing a 0.36$\,$UI sampling time margin with $\rm{BER=10^{-12}}$ at the end of the channel with 11$\,$dB loss at Nyquist frequency. The receiver recovers sampling clock with 1.8$\,$$\rm{ps_{rms}}$ long term absolute jitter while recovering 14$\,$Gb/s data at $\rm{BER=10^{-12}}$. The receiver achieves an energy efficiency of 1.69$\,$mW/Gb/s. Transmitter and receiver share an LC PLL, which achieves 0.605$\,$$\rm{ps_{rms}}$ integrated jitter at 7$\,$GHz output with an energy efficiency of 0.5$\,$mW/GHz. The transceiver as a whole achieves an energy efficiency of 2.8$\,$mW/Gb/s. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-12-01 The student, Saurabh Saxena, accepted the attached license on 2015-11-16 at 16:11. The student, Saurabh Saxena, submitted this Dissertation for approval on 2015-11-16 at 16:37. This Dissertation was approved for publication on 2015-11-18 at 17:00. DSpace SAF Submission Ingestion Package generated from Vireo submission #8792 on 2016-03-02 at 14:13:10 Made available in DSpace on 2016-03-02T21:06:32Z (GMT). No. of bitstreams: 2 SAXENA-DISSERTATION-2015.pdf: 5686569 bytes, checksum: 8aa8ea9b5016dcf7970fa62dc73973b8 (MD5) LICENSE.txt: 4211 bytes, checksum: 69dd22c5bd2c8d283a935e663cca2b14 (MD5) Previous issue date: 2015-11-18 Embargo set by: Seth Robbins for item 91405 Lift date: 2018-03-02T21:07:27Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Limited Restriction Lifted for Item 91405 on 2018-03-03T10:15:31Z. application/pdf http://hdl.handle.net/2142/89202 en Copyright 2015 Saurabh Saxena Serial links Time-based equalization Charge-based flip-flop Charge-based data demultiplexer (DMUX) Clock & data recovery Partially-segmented VM output driver Architectural & circuit level techniques to improve energy efficiency of high speed serial links text text Electrical & Computer Engineering Electrical & Computer Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.