A Low Noise Temperature-to-Digital Converter for a High Stability MEMS-Based Oscillator

Wednesday, October 10, 2012
7:00 PM
Free and open to the public

This talk presents a MEMS-based programmable oscillatorwhich achieves better than +/-0.5ppm frequency stability from -40degrees C to 85 degrees C and less than 1ps (rms) integrated phasenoise (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 oftemperature-induced variation of the MEMS resonant frequency. The TDCutilizes several circuit techniques including a high resolution,tunable reference resistor based on a switched capacitor network andfractional-N frequency division, a switched resistor measurementapproach which allows a pulsed bias technique for reduced noise, and aVCO-based quantizer for digitization of the temperature signal. Toverify the effectiveness of these techniques, measured performance ofa 180nm CMOS IC with co-packaged MEMS die is presented whichdemonstrates 0.1mK (rms) resolution for the TDC within a 5Hz bandwidthand power consumption of 3.97mA with 3.3V supply.

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Michael Perrott

Masdar Institute