Smart Mirrors

Smart rear view car mirror with touch screen

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.

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SiTime MEMS Timing Benefits

Complete MEMS clock tree

Spread spectrum oscillators

Low jitter differential oscillators

32.768-kHz XOs and TCXOs

Precision TCXOs

Most robust in real world conditions

150 fs rms jitter, excellent PSNR

Resistant to shock and vibration

Stable over wide temperature

2.2 billion hours MTBF

Integrated MEMS, easy to use

No quartz reliability issues

Reliable startup in cold temp

No cover or shielding needed

Short lead time for any frequency

Smart Mirrors Block Diagram

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.

MEMS Timing Solutions for Smart Mirrors

Devices Key Features Key Values
Single-ended Oscillator
SiT8924  1 to 110 MHz
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  • Up to -55°C to +125°C
  • ±20 ppm stability
  • 2016, 2520, 3225 packages
  • High reliability
  • Extended temperature range
  • Small footprint
Single-ended Oscillator
SiT9025  1 to 110 MHz
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  • Up to -55°C to +125°C
  • Spread spectrum
  • Configurable rise / fall times
  • 2016, 2520, 3225 packages
  • High reliability
  • Extended temperature range
  • EMI Reduction
Differential Oscillators
SiT9396  1 to 220 MHz
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SiT9397  220 to 920 MHz
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  • Low jitter: < 150 fs RMS [1]
  • ±30, ±50 ppm stability over -40 to +125°C
  • LVPECL, LVDS, HCSL, Low-power HCSL, FlexSwing™
  • 2016, 2520, 3225 packages
  • High reliability
  • Low jitter
  • Enables interfaces with demanding jitter requirements, such as PCI-Express and 10 GB Ethernet
SiT5386  1 to 60 MHz
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SiT5387  60 to 220 MHz
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  • ±0.1, ±0.2, ±0.25 ppm stability over -40 to +125°C
  • ±1 ppb/°C frequency slope
  • Low jitter: 0.31 ps RMS [1]
  • Optional voltage or digital frequency control
  • High accuracy
  • Excellent frequency stability with fast temp gradients
  • No GNSS signal loss or V2X disconnect due to micro-jumps

1 12 kHz to 20 MHz integration range

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.

MEMS Timing Outperforms Quartz

Higher Quality

Higher Reliability

 SiTime – Higher Quality
SiTime timing devices are up to 50x more reliable than legacy quartz


Tighter Stability

Better EMI Reduction

SiTime – Tighter Stability
SiTime – Better EMI Reduction


Immune to Vibration

Better Noise Rejection

SiTime – Immune to Vibration
SiTime – Better Noise Rejection
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