Video processor brings HD quality to backup cameras

Video processor brings HD quality to backup cameras

New Products |
By Christoph Hammerschmidt

Integrating an analog video decoder, two scalers and a MIPI-CSI2 SoC interface, the TW8844 enables the migration from analog to digital camera systems. It supports a variety of video interfaces and LCD panel resolutions up to full HD 1920 x 1080. The TW8844 LCD video processor is ideal for center stack/head units, full display rearview mirrors, instrument cluster displays, and dual headrest rear-seat entertainment systems.

Automakers are starting to make rearview camera systems standard equipment for all new car models worldwide. In the U.S., the National Highway Traffic Safety Administration mandated in March 2014 that automakers implement “rear visibility technology” as standard equipment for all vehicles under 10,000 pounds, as part of the Kids Transportation Safety Act. The new FMVSS-111 regulation specifies that the area behind a vehicle must be visible to the driver when the vehicle is placed into reverse, thereby minimizing blind spots. The law aims to reduce the number of deaths and injuries caused by driver backup accidents, many involving young children. The FMVSS-111 law requires that all new vehicles sold in the U.S., beginning in May 2018, have rearview backup cameras and the rear camera video must display in less than two seconds after the driver places the vehicle into reverse gear. While in Europe no such law is in place, the demand for rearview cameras is rising, in particular in the upmarket and SUV segments.

The TW8844 video processor with MIPI-CSI2 output and its sibling, the TW8845 video processor with BT.656 output, exceed the requirements of the FMVSS-111 law, displaying live video with graphics overlay in less than 0.5 seconds after vehicle ignition. The TW884x provides a robust rear-camera architecture to overcome the fast boot reliability issues inherent with today’s more complex center stack systems. Today’s head units are prone to operating system (OS) software freezes and hang-ups that display a frozen image or prevent the rear camera from displaying live video. With SoCs running increasingly complex operating systems, software freezes and hang-ups are more common. The TW884x eliminates this problem by monitoring the SoC and camera output to determine if they are in a frozen or corrupted state. If the TW884x detects any issue, it bypasses the SoC and instantly displays the rearview camera video.

According to Intersil (now a Renesas activity after it recently has been acquired by the Japanese chipmaker), the frozen-image detection feature is hardwired to trigger an interrupt signal if thresholds are violated, ensuring the vehicle’s rearview camera is FMVSS-111 compliant and live video is instantly displayed. In addition, the TW884x’s rearview camera bypass architecture decouples the camera-to-display signal path from the rest of the infotainment system, which makes attaining an ISO 26262 functional safety rating on the camera system easier for automakers.

The TW8844 and TW8845 can be combined with Renesas’ R-Car SoC family, as well as the ISL78302 dual LDO, ISL78322 dual 2A/1.7A synchronous buck regulator, and ISL78228 dual 800mA synchronous buck regulator to provide power rails for the TW884x, SoC and other key components on the automotive infotainment system board.

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