DIGITALLY ASSISTED ANALOG CIRCUITS PRESENTATION By Sohaib Saadat Afridi MS (EE) SEECS NUST 1

Agenda Introduction Motivation Goals Recent research trends Key Research Labs Published Research Summary Conclusion 2

Introduction Digitally Assisted Analog Circuits. This term was used first as a research title in 2004 [1]. Analog functionalities needed in modern mixed-signal integrated systems [3]. – Signal Conversion (A/D & D/A) – Filtering – Signal Amplification The goal is to implement these functions on CMOS in today's mixed-signal systems. With better efficiency (improve speed & power dissipation) 3

Motivation Progress in digital circuits has outpaced performance growth in analog circuits – High speed – Higher device density – Low power consumption – scalable, synthesizable, and self-testable – Signal processing predominantly done in digital domain Problems in analog circuits on the same level – Non-linearity – Device specific noise – Limitations in accuracy and speed. 4

Goals Reduce power consumption/voltage supply[2 & 3]. Reduce mismatch between different processes[2]. Higher speeds.[2] Improve capacitance linearity [3] Ability to design with reduced element set [3] 5

Digital Processing Signal Conditioning ADC DAC Analog media & transducers Digital Process Minimal Signal Conditioning Minimal Signal Conditioning Low power consuming ADC Low Power consuming DAC Analog media & transducers Post- Processing Pre- Processing Goals [cntd] 6

Recent research trends The areas where aforementioned goals are required – Data Converters – Power Amplifiers – Direct conversion receivers – Delta Sigma Modulators There are many ways to take advantage of digital assistance: – Calibration – Digital compensation for analog impairments – Feedback and feed-forward networks 7

Example 8 A 12-bit 75MS/s Pipelined ADC using Open-loop Residue Amplification

Example[cntd] 9 A 12-bit 75MS/s Pipelined ADC using Open-loop Residue Amplification Conventional Approach

Example(2) 10 A 12-bit 75MS/s Pipelined ADC using Open-loop Residue Amplification Proposed Open Loop Circuit

Key Research Labs Dr. Boris Murmann of the Electrical Engineering Department at Stanford University, USA. – Dr. Joel L. Dawson at Dawson Research Group, MIT,USA. – mtl.mit.edu/~jldawson/research_group/people.html Dr. Christian Vogel at Graz University of Technology, Austria. – 11

Published Research "A 12-bit 75-MS/s pipelined ADC using open-loop residue amplification. "by Murmann, B. and B. E. Boser. IEEE Journal of Solid-State Circuits, Cited by 262 “Digitally assisted analog circuits” by B Murmann; - Micro, IEEE, Cited by 39. “A 5-GHz 20-dBm power amplifier with digitally assisted AM- PM correction in a 90-nm CMOS process” by Palaskas, Y. Taylor;- IEEE Journal of Solid-State Circuits Aug Cited by 19. “Efficiency improvement techniques at low power levels for linear CDMA and WCDMA power amplifiers” by T Fowler, K Burger, NS Cheng,Radio Frequency Integrated Circuits (RFIC) Symposium, Cited by 61 12

Conclusion Digital circuits are most cost and area effective while offering higher yield. Digital assistance will help improve analog circuits to achieve low power consumption, high speed and linearity. It can be achieved through complete transformation of analog circuits into digital circuits or by correction of analog domain issues in the digital domain. 13

References [1] Murmann, B. and B. Boser (2004). "Digitally Assisted Analog Integrated Circuits." Queue 2(1): [2] Murmann, B. (2006). "Digitally assisted analog circuits." Micro, IEEE 26(2): [3] Leme, C. A. and J. E. Franca (1997). Analog- digital design in submicrometric digital CMOS technologies. Circuits and Systems, ISCAS '97., Proceedings of 1997 IEEE International Symposium on. 14