ADAS Computer

ADAS Computer

Modern vehicles are increasingly adopting AD/ADAS functions, generating more data than ever before. Processing this data is possible only through more complex E/E systems, which demand more clocks. High-speed interfaces such as PCI-Express need clocks with well controlled jitter to avoid transmission errors on the bus. Functional safety requirements put further constraints on AD/ADAS components.

SiTime MEMS oscillators offer high reliability and accuracy over temperature from -55 to 125°C in a very small package. Our solutions provide outstanding dynamic performance including excellent stability during rapid temperature change (dF/dT), resilience to shock and vibration, and low jitter. Plus, our FIT rate is up to 50x better than quartz crystal devices, facilitating the achievement of functional safety targets.

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SiTime MEMS Timing Benefits

Complete MEMS clock tree

Spread spectrum oscillators

Low jitter diff. oscillators

32.768-kHz XOs and TCXOs

Precision TCXOs

Most robust in real world conditions

150 fs rms jitter, excellent PSNR

PCIe Gen 4-5 and 10 GB Ethernet

Resistant to shock and vibration

±25, ±30 ppm over -40 to 125°C

>1 billion hours MTBF

Integrated MEMS, easy to use

No external quartz needed

No quartz reliability issues

Reliable startup in cold temp

No cover or shielding needed

Short lead time for any frequency

ADAS Computer block diagramsitime.comDifferential XO SiT9396SSXO SiT9025Diff. XO SiT9396Differential XO SiT939632.768 kHz XO SiT1881Differential XO SiT9396SSXO SiT9025Differential XO SiT9396

MEMS Timing Solutions for ADAS Computer

Devices Function Key Features

SiT9396 Differential XO

SiT9397 Differential XO

Ethernet, PCI-Express, SerDes / PHY clocking 1 MHz to 920 MHz
Ultra-low jitter: 150 fs [1]
±30 ppm over -40 to +125°C
SiT9025 Spread spectrum XO (SSXO) Processor, SoC and general-purpose clocking
EMI reduction

Valid clock output signal
1 MHz to 150 MHz, ±20 ppm over -55 to +125°C
Spread spectrum up to 17 dB reduction
Small size: 2.0 x 1.6 mm package

SiT1881[2] 32.768 kHz XO Reference clock for RTC and safety functions

Ultra-low power: 490 nA
Small size: 1.2 x 1.1 mm package
±20 ppm accuracy over -40 to +105°C
Faster startup time than quartz crystals

SiT5386 Super-TCXO Reference clock for RTC and IEEE 1588/TSN 1 MHz to 220 MHz, -40 to 105°C
±100 ppb over -40 to 105°C,
±1 ppb/°C frequency slope (ΔF/ΔT)

1 RMS phase jitter, integrated over 12 kHz to 20 MHz

2 Contact SiTime for AEC-Q100 version

MEMS Timing Outperforms Quartz

Higher Quality

Higher Reliability

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Automotive Higher Quality graphs

 

Higher Reliability Automotive

 

Tighter Stability

Better EMI Reduction

Tighter Stability Automotive

 

Better EMI Reduction Automotive

 

Immune to Vibration

Better Noise Rejection

Immune to Vibration Automotive Better Noise Rejection Automotive

Reliable Clocks are Essential for ADAS

ADAS (Advanced Driver Assistance System) computers are the brains of tomorrow’s self-driving cars. They collect data from various sensors such as Radar, LiDAR and camera systems. The data is processed, “driving” decisions are made, and control commands are issued to the various systems of the vehicle (powertrain, steering, brakes, etc.)

ADAS computers require several clocks.

  • A low jitter clock is essential to ensure proper PHY operation since data input usually occurs through a PHY (such as MIPI A-PHY, FPDLink, GMSL, etc.).
  • PCI-Express is widely used for on-board, device-to-device data exchange. This requires 100 MHz differential clocks, possibly with spread spectrum.
  • Multi-GB Ethernet for board-to-board communications requires 156.25-MHz, differential, low jitter clocks.
  • SoC, processors, and other devices require general purpose clocks.
  • A 32.768-kHz clock is necessary for time keeping and, in some systems, for safety functions.

SiTime oscillators offer several advantages over quartz crystals that are particularly important for automotive applications.

  • Up to 50x better reliability. Apart from reducing the amount of field failures, 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.
  • Up to 100x better resilience to shock, vibration, and electromagnetic interference, due to the smaller size (0.4 x 0.4mm) and lower mass of MEMS resonators compared to crystals.
  • Better frequency stability (down to ±100 ppb) and frequency response to temperature changes dF/dT (down to < ±1 ppb/°C). These characteristics provide better locking to GNSS and V2X, and avoid connection drops.

Watch Video: SiTime MEMS Oscillators for ADAS

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