Disadvantages of Quartz Timing
In order to maintain the smooth operation of the car system, a single car currently uses up to 70 timing devices. This number continues to grow as more and more cars deploy smarter technology in new models. Clock generators and oscillators provide precise and reliable timing references for various digital systems in automotive designs. They will all provide critical timing functions in electronic control units (ECUs) for ADAS, in-vehicle networking, infotainment and other subsystems.
Timing devices help synchronize the rapid, continuous transfer of data from the various sensors to the ADAS computer. They are also crucial in vehicle-to-vehicle communications (V2X) and 5G communications. Second, timing is also the foundation upon which Global Navigation Satellite Systems (GNSS) are built, including the Global Positioning System (GPS) technology at the heart of telematics.
Yet despite the accelerating pace of automotive innovation, one critical electronic component remains stuck in the slow lane: quartz timepieces. Historically, the most common clock source across all industries and applications has been the crystal oscillator (XO). The 70-year-old technology has matured to a point where progress is minimal. Furthermore, quartz crystals have inherent limitations such as fragility and sensitivity to mechanical and environmental stress.
As the complexity of automotive systems increases, quartz timing devices are increasingly becoming a reliability and safety bottleneck due to their inherent flaws. These limitations drive up cost and complexity and limit system reliability.
In addition, automotive electronics often operate in harsh environments and are subject to mechanical shock and vibration, temperature fluctuations, and electromagnetic interference. Constant vibration from rough roads and moving parts can also have a damaging effect on sensitive electronic components such as quartz timing devices.
Second, automotive applications must support an ultra-wide temperature range from −40°C to +125°C, and there will be an increasing demand for normal operation at high temperatures up to +150°C in the future. In addition to the heat generated by the engine or battery pack, changing climatic conditions can cause temperature extremes that can degrade the accuracy of quartz-based components. The sensitivity of quartz timing to environmental stressors will also negatively impact the performance and reliability of automotive systems ranging from ADAS to battery management systems.
MEMS Timing Technology
Timing devices based on microelectromechanical systems (MEMS) technology are disrupting today’s clock market. They serve as excellent replacements for quartz components in high-reliability applications where systems such as ADAS and electric vehicle battery management face environmental stress.
MEMS is a proven and mature technology used in electronic systems ranging from automobiles to smartphones to industrial and aerospace applications. MEMS devices can be used in gyroscopes, accelerometers (for airbag deployment), microphones, speakers, magnetometers and various types of sensors.
Automotive safety systems were one of the first applications to adopt MEMS technology as it required exceptional ruggedness and reliability in harsh environments. Silicon MEMS devices are also suitable for mass fabrication in mainstream fabs, thus enabling high-volume, cost-effective solutions for demanding automotive applications.
MEMS timing components, like their quartz equivalents, are engineered to meet the stringent AEC-Q100 automotive qualification requirements. This certification standard provides automakers with assurance that certified timing components provide the robustness, reliability, and high performance required for automotive electronic systems. Traditional quartz devices are usually only able to comply with the less stringent AEC-Q200 specification for passive components.
Precision timing devices based on silicon MEMS technology with a proven track record in demanding automotive applications. Designed to withstand environmental stress, MEMS-based timing devices ensure reliable operation of ADAS computers, zone/area controllers, radar, and lidar subsystems.
Rigorous testing has shown that silicon MEMS technology is far more reliable than quartz crystals for clock applications. This reliability is measured in the number of failures or failure rate (FIT) per 109 hours of operation. Due to the large test time span of 109 hours, the industry generally uses statistical analysis and accelerated models to determine the failure rate. The failure rate of MEMS timing devices is <0.5FIT, which is equivalent to MTTF>2 billion hours under the condition of 90% confidence level, which is 50 times higher than that of quartz-based timing technology.
Advantages of MEMS
Component size is also critical in today’s highly integrated automotive system designs. MEMS resonators are much smaller than quartz crystals, so the footprint of the timing device is smaller, down to 1.0×1.2mm, which makes MEMS devices ideal for space-sensitive applications such as camera modules, smart mirrors, and radar/lidar sensors. Ideal for automotive applications. In timing device design, smaller size and lighter mass also tend to make the product more resilient when faced with mechanical shock and vibration.
MEMS resonators are also 100 times more resistant to EMI interference compared to quartz. High interference immunity is especially beneficial for applications such as battery management systems in electric vehicles, which are subject to high currents and electromagnetic fields.
Silicon MEMS technology also has inherent material properties that are superior to quartz. For example, SiTime’s MHz oscillators offer ±20ppm frequency stability over the -55°C to 125°C range. Compared with quartz, MEMS has more than 2 times the frequency stability, 20 times the reliability, and 30 times the shock and vibration resistance.
Integrated temperature compensation, a key feature of MHz-class oscillators, improves frequency stability to ±0.1ppm, an added advantage under harsh operating conditions with extreme temperature fluctuations and other environmental hazards. Higher frequency stability improves timing accuracy, enabling higher synchronization performance for V2X and 5G communications over an extremely wide temperature range.
MEMS timing devices do not have the “cold cranking problem” at the bottom of the temperature range that often plagues quartz-based oscillator systems. In addition, silicon MEMS resonators are not affected by so-called “micro jumps”. When using quartz crystal oscillators, this common random and non-reproducible frequency jump “micro jump” may cause signal loss in GNSS/GPS or V2X/5G communication.
The Future of The Automotive Industry
The future of the automotive market will be defined by the enormous technological innovations and rapid advancements in electronics today. Timing components are a key part of this future.
Future smart connected cars and safety-critical systems require timing components designed to deliver the highest reliability, performance and stability. By moving from traditional quartz technology to MEMS-based precision timing solutions, automakers are making strategic investments in safer, more reliable automotive system designs.