Intersil - Video SerDes Transceiver Targeting Automotive Rear View Video Safety Systems

The ISL76321 concentrates up to 16-bits wide video data and bi-directional I2C control information onto a single high-speed STP cable, and can transmit data in excess of 20 meters. Remote control of the far end of the link, an attractive feature of the ISL76321, allows a controller to access an imager via its I2C interface through which operating modes and adjustments, such as exposure and windowing, can be made. Ultimately this feature facilitates camera operation under dynamically changing conditions. Sending control data over the same cable as the video data eliminates unnecessary complexity in wiring looms and reduces weight.

A camera link comprises a pair of ISL76321s connected via a single STP cable to establish a high resolution, serial data link between a remote video camera and a central control unit. This interface transceiver accommodates a wide pixel clock range from 8MHz to 50MHz, and raw data rates up to 1000Mbps. This provides a robust link for a host of automotive video-based passive and active safety systems including Lane Departure Warning, Signpost Recognition and Pedestrian Avoidance systems. Interest in such systems is increasing, as demonstrated by recent statements from the U.S. auto-safety regulator (the National Highway Traffic Safety Administration) with proposals for backup cameras on all new vehicles in the U.S. by 2014 to reduce the dangers of drivers backing over pedestrians.

The ISL76321 uses industry standard 8b/10b encoding to improve signal integrity as well as giving the link hot plugging capability. Even in the noisiest environments, the unique, fast line-rate locking PLL system (10 microseconds to lock compared to >10 milliseconds with competing devices) helps ensure the reliability of the link - a key factor in safety-critical systems.

The ISL76321 enhances range by adding transmission pre-emphasis and cable equalization (EQ). These features have 16 levels of programmability, enabling the product to drive 20 meters of cable with multiple in-line connectors. Alternatively, in shorter distance applications the ISL76321 permits the use of lower cost cables to further reduce system costs. The transceivers' EQ increases the signal-to-noise ratio at the receiver end with no increase to radiated EMI.

Finally, Intersil's solution helps to facilitate the implementation of a low cost power-over-LVDS scheme for modest load currents (up to one amp). Such a system can supply remote end power over the same STP cable, further reducing wiring loom complexity, cost and weight, along with simplifying the OEM installation challenges.