—This paper describes the first precision 32kHz low-power MEMS-based oscillator in production. The primary goal is to provide a small form-factor oscillator (1.5 x 0.8 mm 2 ) for use as a crystal replacement in space-constrained mobile devices. The oscillator generates an output frequency of 32.768kHz and its binary divisors down to 1Hz. The frequency stability over the industrial temperature range (-40°C to 85°C) is ±100ppm as an oscillator (XO) or ±3ppm with optional calibration as a temperature compensated oscillator (TCXO). Supply currents are 0.9µA for the XO and 1.0µA for the TCXO at supply voltages from 1.4V to 4.5V. The MEMS resonator is a capacitively-transduced tuning fork at 524kHz. The circuitry is fabricated in 180-nm CMOS and includes low power sustaining circuit, fractional-N PLL, temperature sensor, digital control, and low swing driver.

This paper presents a dual-microelectromechanical system (MEMS) resonator-based temperature sensor. In this sensor, the readout circuit estimates the temperature by measuring the frequency ratio of the two clocks generated by separate resonators with different temperature coefficients. The circuit is realized in a 0.18-μm CMOS process and achieves a resolution of 20 μK over a bandwidth of 100 Hz while consuming 19 mW of power, leading to a resolution FOM of 0.04 pJK 2 . It enables us to implement a MEMS-based programmable oscillator with an Allan deviation of <;1e -10 over 1 s averaging time, and a frequency stability of <;±0.1 parts per million in the temperature range from -45 °C to 105 °C. Such oscillators are key building blocks in telecom, datacom, and precision timekeeping applications.

The papers in this special section were presented at the 2015 Joint Conference of the IEEE International Frequency Control Symposium & European Frequency and Time Forum that was held in Denver, Colorado, April 12-16, 2015.

This paper describes the first 32 kHz low-power MEMS-based oscillator in production. The primary goal is to provide a small form-factor oscillator (1.5 × 0.8 mm 2 ) for use as a crystal replacement in space-constrained mobile devices. The oscillator generates an output frequency of 32.768 kHz and its binary divisors down to 1 Hz. The frequency stability over the industrial temperature range (-40 °C to 85 °C) is ±100 ppm as an oscillator (XO) or ±3 ppm with optional calibration as a temperature compensated oscillator (TCXO). Supply currents are 0.9 μA for the XO and 1.0 μA for the TCXO at supply voltages from 1.4 V to 4.5 V. The MEMS resonator is a capacitively-transduced tuning fork at 524 kHz. The circuitry is fabricated in 180 nm CMOS and includes low power sustaining circuit, fractional-N PLL, temperature sensor, digital control, and low swing driver.

Research on MEMS Resonators began over 50 years ago. In just the last 10 years, there has been a series of important technological developments, and (finally!) success at commercialization. The presentation will highlight some key milestones along this path, describe some of the critical technology steps, and outline some of the important non-technological events within SiTime - all of these factors contributed to the successful outcome.

Real-time clocking for space-constrained mobile and wearable applications require low-power 32.768 kHz references with small form-factor and tight frequency stability, at a competitive price built in an ultra-high volume capable manufacturing process. Legacy 32 kHz quartz-based technology has reached the limits of miniaturization, performance and cost. In this work, a temperature compensated 32 kHz MEMS-based oscillator (TCXO), in a 1.55 mm × 0.85 mm × 0.55 mm form factor, with ±5 ppm frequency stability over -40°C to 85°C, will be presented. The combination of wafer-level chip scale packaging (WL-CSP) and silicon MEMS technology has enabled the smallest and best-in-class 32 kHz clocking solution for very high volume applications. The underlying MEMS system packaging and test technologies will be presented along with the electrical and reliability results.

Lists the sessions held at the conference proceedings.

MEMS-based oscillators offer a silicon-based alternative to quartz-based frequency references. Here, a MEMS-based programmable oscillator is presented which achieves better than ±0.5-ppm frequency stability from -40 ° C to 85 ° C and less than 1-ps (rms) integrated phase noise (12 kHz to 20 MHz). A key component of this system is a thermistor-based temperature-to-digital converter (TDC) which 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. The TDC achieves 0.1-mK (rms) resolution within a 5-Hz bandwidth while consuming only 3.97 mA for all analog and digital circuits at 3.3-V supply in 180-nm CMOS.