Feature: Automotive Design
Accurate
Silicon Timing boosts Smart- Driving
Systems By Sumeet Kulkarni, director of product marketing, Automotive, SiTime
Automotive Timing Requirements Te latest new car models entering the market contain increasingly powerful, intelligent and autonomous systems needed to enhance safety, increase comfort and add value for owners and occupants. Tese systems handle vast quantities of data to deliver infotainment services, exchange mission-critical and safety-critical data, establish location awareness and contextual sensitivity, and dynamically control the vehicle. Consistent, accurate and precise timing is critical for operating each electronic control unit (ECU) as a high-performing embedded system, and to coordinate high-speed data exchanges using popular protocols such as PCI Express and automotive Ethernet. However, as automotive system performance demands increase
and as new and more exacting specifications are adopted in response, electronic systems designers need a combination of performance, reliability and efficiency beyond the reach of conventional quartz-based timing sources. MEMS-based alternatives that are more robust, smaller and lightweight than quartz, as well as consuming lower power, can better satisfy performance requirements and stand up to life on the road. High accuracy and stability are crucial to handle high volumes of
sensor data, operating across wide-ranging environmental conditions. Suitable timing devices must be able to effectively manage multi-gigabit interfaces and ensure seamless communications between internal and external vehicle systems, including emerging vehicle-to-everything (V2X) connectivity. Leveraging the latest MEMS technology, silicon-based oscillators
can be produced to high quality standards and meet the exacting performance requirements for advanced automotive applications. Tey offer smaller dimensions, greater resilience, and lower power consumption. In addition, MEMS timing devices allow 15 different parameters, including frequency, operating temperature range and supply voltage to be programmed to meet specific application requirements. Tis contrasts with quartz crystals, which are manufactured to have a single, fixed frequency. On the other hand, silicon-based devices can be built using robust and proven CMOS processes that allow high production yield.
Fabrication and Packaging Advancements Important advancements in device fabrication and packaging now enable silicon-based oscillators to combine high frequency stability with reliability, ruggedness, miniaturisation and energy efficiency that are superior to traditional quartz-based devices. MEMS resonators made in monocrystalline silicon can be just a
few tenths of a millimetre in size, about 200 μm x 200 μm. Moreover, having as much as 1000-times lower mass than a quartz resonator, their vibration resistance is far greater because an acceleration imposed on the MEMS structure results in a much lower force and frequency shiſt. Historically, packaging has been a key challenge and a barrier to the
commercialisation of MEMS resonators. However, advancements in fabrication and sealing processes let manufacturers produce finished wafers with hermetically sealed resonators enclosed within individual micro-vacuum chambers. Te hermetic sealing is performed at high temperature and in a clean vacuum environment. Unlike the conventional low-temperature packaging processes used to manufacture quartz-based devices, this ensures no volatile organic chemicals or
18 October 2024
www.electronicsworld.co.uk
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