Smart Mirrors

Smart mirrors are replacing traditional mirrors because of the many advantages they offer. They rely on several building blocks that must be clocked with reliable timing solutions as video data is processed and transmitted. SiTime MEMS oscillators provide up to 50x better reliability compared to quartz products. Plus they offer resilience against shock and vibration, low jitter, higher accuracy over temp, and unique EMI features – all in a small package.

Download Application Brief

Smart mirrors replace traditional mirrors by displaying images from a camera onto an LCD display. The architecture of windshield-mounted rear-view "mirrors" can be different from side-view "mirrors.". In the former, the LCD is an integral part of the system, while the latter display the image on LCDs located elsewhere, on the instrumentation dashboard, or even in the doors.

Regardless of architecture differences, smart mirrors rely on several building blocks: an imager, a system-on-chip for processing, and one or more LCD displays. Interfaces are necessary to transmit or receive video data to/from other sources. Switching image sources – for instance from a camera mimicking a rear-view mirror in normal driving, to a close-up backup camera while maneuvering – provides real advantages to the driver but complexifies the architecture to some extent.

Smart Mirror Clocks

Several clocks are typically needed in a smart mirror system.

• CMOS imager clock: usually a single-ended clock, for instance 27 MHz
• SoC clock: usually a single-ended clock, in the range 16 – 40 MHz
• Interface / PHY clock: depending on the interface, either single-ended or differential: single-ended 25 MHz for GMSL, single-ended 27 MHz for FPD-Link, single-ended 25 MHz for Ethernet, differential 156.25 MHz for 16 GB Ethernet, etc.

Note that the exact clocks required depend on architecture and components used.
 

SiTime Advantages

SiTime devices offer the following advantages over quartz crystals, which are particularly important for automotive applications:

• 50x better reliability: Apart from reducing the amount of field failures, the better reliability translates into a lower FIT rate. This provides better hardware safety metrics in an FMEDA, the quantitative analysis required as part of a functional safety assessment.
• 10x better resilience to shock, vibration and electromagnetic interference, due to the smaller size (0.4 x 0.4 mm) and lower mass of MEMS resonators compared to crystals. When not causing permanent damage to the crystal, shock and vibration can induce jitter in a crystal oscillator. Jitter can be detrimental to the bit error rate of a high-speed link. The better resilience of SiTime oscillators ensures a low error rate regardless of operating conditions.
• A typical requirement of clocks for data interface is: "the faster the interface, the lower the clock jitter.". The jitter of the clocks must be below a certain limit defined by the chipset manufacturer. SiTime devices offer state-of the art jitter performance.
• Small footprint: Due to the small size of the silicon MEMS resonator, SiTime devices have a very small footprint – down to 1.2 x 1.1 mm. This is of advantage in space-constrained applications.

Additional Resources

• Timing Solutions for Automotive Systems
• Increase automotive reliability and performance with ultra-robust MEMS oscillators
• AEC-Q100 Automotive Oscillators for ADAS Sensors, in-Vehicle Networking & Self-Driving Computer
• EMI Reduction Oscillators for Industrial, Automotive and Consumer Applications
• Automotive Cameras