Oregon State University

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Event Details

PhD Final Oral Examination – Hariprasath Venkatram

Tuesday, August 20, 2013 3:00 PM - 5:00 PM

Energy and Area Efficient Data Converter Techniques
Data converters are ubiquitous building blocks of a signal chain. The rapid increase in communication and connectivity devices presents new avenues for pushing the state of the art analog to digital converters. Techniques for improving resolution, bandwidth, linearity and bit-error rate, while reducing the power, energy and area is the motivation for this research. This research focuses on achieving this goal by enabling circuit techniques, architecture techniques and calibration methods.

The following techniques are proposed for enabling power, area and energy efficient analog to digital converter techniques.

Circuit Techniques

1.    A capacitor switching scheme for successive approximation ADC is introduced to enable 93.4% energy reduction and 75 % reduction in capacitor area as compared to a conventional SAR ADCs.

2.    Asynchronous correlated level shifting technique for improving current source linearity and power supply rejection ratio of zero crossing based circuits is proposed. This technique enables asynchronous ADC architectures for energy efficient system.

3.    Unified gain enhancement model is proposed to catalogue gain enhancement techniques. Class-A+ and Replicated Parallel Gain Enhancement (RPGe) amplifiers are introduced as parallel gain enhancement techniques for switched capacitor circuits. A prototype pipelined ADC using RPGe amplifier achieves 74.7 dB SNDR, 90.8 dB SFDR, 87 dB THD at 20 MS/s. Built in 1P4M 0.18 mm technology and operating at 1.4 V supply, the ADC consumes 6.77 mW. The ADC occupies 3.06 mm2 and has a figure of merit of 75 fJ /conversion step.

4.    A low-gain amplifier based V-T converter is utilized along with a TDC to replace the function of flash ADC and the DAC references in a pipeline ADC. The simulated/extracted performance of the chip is 12bit, 100 MHz in 65nm process while consuming approximately 9-9.2 mA from 1 V supply.

Architecture/Calibration Methods

5.   A measurement technique for detecting and correcting bit-error rate in ADCs is proposed. This multi-path ADC technique squares the bit-error rate of the ADC without consuming additional analog power. The area increase is negligible compared to the conventional modular redundancy techniques. This technique can be applied to digitally detect and correct single event transients for ADCs. A three-path ADC can restore the ADC performance independent of the input frequency and number of errors in a single path.

6.    LMS algorithm is used to estimate the VCO non-linearity by using the VCO as a Nyquist ADC and utilizing a slow but accurate ADC. The simulated ADC performance improves from 5 bits to 7.8 bits by using a second order fit to the VCO non-linearity.

Major Advisor: Un-Ku Moon
Committee: Gabor Temes
Committee: Raviv Raich
Committee: Alan Wang
GCR: Leonard Coop

Kelley Engineering Center (campus map)
Nicole Thompson
1 541 737 7234
Nicole.Thompson at oregonstate.edu
Sch Elect Engr/Comp Sci
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