4-ch video decoder for automotive surround-vision has MIPI-CSI2 interface

September 19, 2016 // By Graham Prophet
Intersil’s ISL79985/86 parts are four-channel analogue video decoders that are configured to route camera feeds to image processors in automotive vision systems. The -85 part has a MIPI-CSI2 interface (parallel-bus interfaces have been standard in this context); the -86 device multiplexes all four camera feed on to a 4x speed, 8-bit bus.

These parts continue the family of vision-oriented devices that Intersil acquired when it purchased Techwell in 2010. Intersil itself is now to be acquired by Renesas ; which is not the first time that the Intersil name will have been absorbed into another entity. The original Intersil was taken over by Harris; Harris resurrected the brand when spinning out the semiconductor operation, once again, in 1999.


One of the immediate drivers for this update of vision processing components is the requirement that by model year 2018, all vehicles in the US must have reversing (“back-up”) camera systems that. One parameter of this specification is that the rear-view camera systems must boot-up quickly, in less than 2 seconds, so that the reversing image is available immediately to the driver upon starting the car.


This is implemented as part of the function envisaged for the integrated ISL79985, which generates a 360-degree birds-eye-view, quality image for advanced driver assistance systems. It is positioned as the first four-channel analogue video decoder with MIPI-CSI2 output interface that supports the latest generation of SOCs and application processors. The ISL79985 replaces up to nine discrete components with a single chip to preserve critical board space. The ISL7998x family also includes the new ISL79986 with a line-interleaved BT.656 interface, at a 108-MHz rate.


The ISL79985 and ISL79986 integrate four analogue video decoders with 10-bit ADCs to support four analogue camera CVBS inputs simultaneously. The ISL79985’s MIPI-CSI2 interface lowers system EMI, reduces the number of pins compared to a traditional parallel interface, and makes it easy to interface with the newest SOCs and ADAS processors.


An issue with small cameras in ADAS systems can be dynamic range and contrast; critical image information can be washed-out or suppressed. Both decoders include Intersil’s proprietary automatic contrast adjustment (ACA) image enhancement feature that adapts to rapidly changing lighting conditions. ACA is able to automatically increase or reduce brightness