New Electronics – ST Unveils Advanced Global Shutter Image Sensor

STMicroelectronics has developed a global shutter image sensor for driver monitoring systems (DMS).

DMS continuously monitors the driver’s head movements to recognize signs of drowsiness and distraction, allowing vehicle systems to generate warnings that can keep occupants safe.

Traffic agencies estimate that around 95% of traffic accidents result from human error, many of which could be avoided by using systems such as DMS. With nearly 19,000 fatal accidents in Europe in 2020, recently enacted legislation will make DMS mandatory for all new automotive platforms in Europe in 2024 and for existing model platforms in 2026.

In fact, with road deaths twice as high in the United States, the National Transportation Safety Board (NTSB) has recommended DMS for all semi-autonomous vehicles.

“Drivers may not realize they cannot drive safely due to fatigue or distraction. DMS removes uncertainty by automatically detecting the issue, protecting all occupants as well as other people traveling on the road,” said Eric Aussedat, executive vice president, general manager, Imaging Subgroup, STMicroelectronics. “Our latest global shutter sensors offer sensitivity and compactness, simplifying DMS hardware and reducing the overall cost of system. This allows our customers and partners to provide efficient and reliable DMS systems that meet the expectations of the legislation.

The global shutter sensor, the VB56G4A, leverages ST’s in-house investment in manufacturing advanced 3D stacked back-illuminated image sensors (BSI-3D). These are more sensitive, smaller, and more reliable than conventional front-illuminated (FSI) sensors typically used in first-generation DMSs.

ST is now supplying samples of its new sensor to major customers, and mass production is scheduled for early 2023 for adoption in model year 2024 vehicles.

The global shutter sensor offers a number of advantages over rolling shutter imagers. By simultaneously exposing all pixels in the image, a global shutter sensor enables simple synchronization with NIR illumination, improving the power budget of the illumination subsystem. Additionally, the sensor achieves high quantum efficiency (QE), reaching 24% at a near-infrared wavelength of 940 nm, with a linear dynamic range down to 60 dB allowing a simple low-power LED emitter and no visible to provide adequate illumination for the sensor.

Operation outside of the visible spectrum also ensures consistent response in day or night riding and in bright or overcast conditions.

The sensor’s high QE, combined with a pixel size of just 2.6 µm, also helps to optimize overall power consumption and camera size. Additionally, the built-in automatic exposure control provides ease of use and simplifies application software design by minimizing system interaction with the sensor.

The sensor also provides flexible operating modes that help optimize system functionality and performance. These include programmable sequences of 4-frame contexts, illumination control outputs synchronized with sensor integration periods, input for an external frame start signal, automatic dark calibration, dynamic pixel correction, image cropping and mirror/reverse image playback. .

External connections include eight General Purpose Programmable I/O (GPIO) pins and a dual-lane MIPI CSI-2 transmitter interface operating at up to 1.5 Gbps per lane. The sensor can operate at up to 88 frames per second (fps) at full resolution and typical power consumption is 145 mW at 60 fps.

Michael C. Garrison