Automotive Cameras

Automotive camera modules present several design challenges. Board space is constrained. Environmental conditions include extreme temperatures, fast temperature changes, shock, vibration, and electromagnetic interference. Increasing sensor resolution means higher data rates, which requires low jitter clocking.

SiTime MEMS-based oscillators meet these challenges. They offer small size, accuracy over temperature from -55 to 125°C (even with fast temp ramp), low jitter, resilience to shock and vibration, and EMI reduction features. Our devices have higher quality and reliability, with a FIT rate that is up to 50x better than quartz crystal devices to help systems meet functional safety metrics targets.

Download Application Brief

Cameras are built around an imager, of varying resolution depending on the camera’s purpose. After some processing, the data stream is sent to the vehicle’s ADAS computer by means of a serial interface. The most common kinds of PHY are MIPI A-PHY (Valens), FPDLink (TI), and GMSL (Analog Devices). Both imager and PHY require a high quality, low jitter clock to operate.

Cameras are usually complemented with radar, lidar and infrared sensors.

See also the Application Brief on ADAS Computer.

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.
• 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
• ADAS Computer