DIGITALLY ASSISTED ANALOG CIRCUITS

PRESENTATION By

Sohaib Saadat AfridiMS (EE) SEECS NUST

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Agenda

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

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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)

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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.

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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]

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Digital Processing

Signal Conditioning

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]

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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

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Example

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

Example[cntd]

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

Conventional Approach

Example(2)

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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.– http://www.stanford.edu/group/murmann_group/

• Dr . Joel L. Dawson at Dawson Research Group, MIT,USA.– http://www-mtl.mit.edu/~jldawson/research_group/

people.html• Dr. Christian Vogel at Graz University of

Technology, Austria.– http://www2.spsc.tugraz.at/people/cvogel/index.html

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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,2005. -Cited by 262

• “Digitally assisted analog circuits” by B Murmann; - Micro, IEEE, 2006. 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. 2006 - 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, 2002 -Cited by 61

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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.

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References

• [1] Murmann, B. and B. Boser (2004). "Digitally Assisted Analog Integrated Circuits." Queue 2(1): 64-71.

• [2] Murmann, B. (2006). "Digitally assisted analog circuits." Micro, IEEE 26(2): 38-47.

• [3] Leme, C. A. and J. E. Franca (1997). Analog-digital design in submicrometric digital CMOS technologies. Circuits and Systems, 1997. ISCAS '97., Proceedings of 1997 IEEE International Symposium on.

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