ICS Seminar: Prof. Michael Perrott
Thursday, October 11, 2012
6:00-8:00pm
ACE 2.402
First Talk Abstract:
VCO-based quantizers take advantage of the steadily increasing speed of modern CMOS processes by quantizing time rather than amplitude. Their implementation leads to highly digital architectures that benefit directly from Moore’s law, and offer intriguing benefits such as inherent shaping of their quantization noise. In this talk, we examine their potential for achieving high resolution analog-to-digital conversion (ADC), and identify key shortcomings such as nonlinearity of the voltage-to-frequency characteristic and its impact on SNDR. Circuit techniques are then presented to overcome such shortcomings, along with recent results verifying their effectiveness. In particular, we show that using phase rather than frequency within a continuous-time Sigma-Delta ADC topology enables 78dB SNDR performance within 20MHz bandwidth with a power efficiency of 330 fJ/conversion step. Finally, we conclude by generalizing the VCO-based quantizer as an efficient combination of a voltage-to-time converter and a time-to-digital converter, and discuss its advantages compared to other recent approaches which combine these components.
Second Talk Abstract:
This talk presents a MEMS-based programmable oscillator which achieves better than +/-0.5ppm frequency stability from -40 degrees C to 85 degrees C and less than 1ps (rms) integrated phase noise (12kHz to 20MHz). We focus on the key component of this system, which is a thermistor-based temperature-to-digital converter (TDC) that enables accurate and low noise compensation of temperature-induced variation of the MEMS resonant frequency. The TDC utilizes several circuit techniques including a high resolution, tunable reference resistor based on a switched capacitor network and fractional-N frequency division, a switched resistor measurement approach which allows a pulsed bias technique for reduced noise, and a VCO-based quantizer for digitization of the temperature signal. To verify the effectiveness of these techniques, measured performance of a 180nm CMOS IC with co-packaged MEMS die is presented which demonstrates 0.1mK (rms) resolution for the TDC within a 5Hz bandwidth and power consumption of 3.97mA with 3.3V supply.
Biography:
Michael H. Perrott received the B.S. degree in Electrical Engineering from New Mexico State University, Las Cruces, NM in 1988, and the M.S. and Ph.D. degrees in Electrical Engineering and Computer Science from Massachusetts Institute of Technology in 1992 and 1997, respectively. From 1997 to 1998, he worked at Hewlett-Packard Laboratories in Palo Alto, CA, on high speed circuit techniques for Sigma-Delta synthesizers. In 1999, he was a visiting Assistant Professor at the Hong Kong University of Science and Technology. From 1999 to 2001, he worked at Silicon Laboratories in Austin, TX, and developed circuit and signal processing techniques to achieve high performance clock and data recovery circuits. He was an Assistant and then Associate Professor in Electrical Engineering and Computer Science at the Massachusetts Institute of Technology from 2001 to 2008. He was with SiTime Corporation from 2008 to 2010, where he developed key technology for MEMS-based oscillators. He is currently a professor at Masdar Institute in Abu Dhabi, where he is focusing on low power, mixed-signal circuits for health and fitness and other applications.