MEMS Oscillators with Improved Resilience for Harsh Automotive Environments 2016-01-0101
Oscillators are key components in automotive electronics systems. For example, a typical automotive camera module may have three or more oscillators, providing the clocks for microcontrollers, Ethernet controllers, and video chipsets. These oscillators have historically been built around a quartz crystal resonator connected to an analog sustaining circuit driving the crystal to vibrate at its resonant frequency. However, quartz-based devices suffer from poor performance and reliability in harsh automotive environments. SiTime has developed timing solutions based on silicon micro-electromechanical systems (MEMS) technology that exhibit better electromagnetic noise rejection and better performance under shock and vibration. In this paper, we first discuss the design and manufacturing of the MEMS-based device, with emphasis on the specific design aspects that improve reliability and resilience in harsh automotive environments. These aspects include the SOI-based MEMS fabrication process, the oscillator and state-of-the-art temperature compensation architecture, and the manufacturing and packaging process. We then describe the test methods used to evaluate the resilience of the device, including electromagnetic susceptibility (EMS), and performance during shock and vibration. The results show that the MEMS-based oscillator performs better than all quartz oscillators that were tested, with up to 50x better EMS, up to 24x better performance during shock, and up to 100x and 20x better performance during sinusoidal and random vibration, respectively.