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.

Download Application Brief

ADAS computers require many 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 – the SiT9025 is perfect for EMI reduction.
• Multi-GB Ethernet for communications require 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.

See also the Application Brief on Automotive Cameras.

Key concerns of designers

• Reliability
• Functional safety
• High temperature requirements
• Fast system startup time required (usually < 100 ms)
• EMI

SiTime advantages

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

• Up to 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.
• Up to 100x 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.
• Better frequency stability (down to ±100 ppb) and frequency response to temperature changes dF/dT (down to < 3.5 ppb/°C). These characteristics provide better locking to GNSS and V2X, and reduced connection drops.
• Silicon MEMS oscillators typically have a faster start-up time than crystal oscillators.
• SiT9025 features EMI reduction features: spread spectrum and configurable rise/fall times

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