MEMS Oscillators Revolutionizing the Precision Timing Market

Abstract

Frequency references are the heartbeat of most electronic systems. Over the last decade, MEMS-based frequency references have revolutionized the timing market by outperforming quartz crystal oscillators in many applications, where they can offer lower power, smaller size, better stability, programmability, and higher reliability. In this chapter, a MEMS-based temperature-compensated oscillator (TCXO) is presented which achieves a frequency stability of <±100 parts per billion (ppb) in the temperature range from −45 to 105 °C and an Allan deviation (ADEV) of <2e⁻¹¹ over 1 s averaging time. The result of an improved version of this TCXO is also presented where the frequency stability over temperature is improved by over tenfold, to <±10 ppb, which matches the performance of entry-level quartz-based OCXOs. Such oscillators are key building blocks in telecom, networking, and precision timekee** systems. To enable such performance, SiTime’s DualMEMS™ technology is used for temperature-to-digital conversion (TDC). This technology enables the design of high-precision temperature-compensated MEMS-based oscillators with superior performance for applications in breezy conditions and harsh environments. The TDC 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 pJ°C2. Measurement results supporting the applications in harsh environments are presented, while a comparison with the high-performance quartz crystal TCXO solutions will be also provided.