Enabling Advanced In-Vehicle Infotainment Video Conversions with ROHM’s ML86795 Interface Bridge IC

Abstract 

In-vehicle infotainment (IVI) systems in modern automobiles offer drivers and passengers an unprecedented level of connectivity, entertainment, and functionality. High-resolution displays and immersive graphics, video streaming, and real-time camera feeds are just a few ways video technology has transformed how information is displayed and accessed in vehicles. However, the increased complexity and diversity of video interfaces in automotive systems remain key challenges for designers. This paper explores trends and challenges in interface conversion in IVI systems, and introduces ROHM’s solution for addressing these challenges. 

Current IVI Trends and Challenges in the Automotive Industry

Automakers have moved towards manufacturing vehicles with higher-resolution displays and cameras, due to increasing user demands for advanced driver assistance systems (ADAS) and other immersive in-vehicle experiences. This trend has led manufacturers to adopt various video interface standards within vehicles, including LVDS and MIPI CSI-2, each with its unique characteristics and benefits. Infotainment systems must now support a wide range of formats and resolutions, from legacy standard-definition interfaces to cutting-edge high-definition and ultra-high-definition. Interface diversification, however, represents a challenge for designers who must ensure compatibility and interoperability between the various components of the IVI system. Generally, automakers buy components from suppliers, such as a camera module, ECU or display, and then combine the components to complete the car. In this case, the interface formats of camera modules, displays, and system-on-chips (SoCs) may be mismatched, so the camera module or display must be adapted to the interface of the SoC, or the SoC must be adapted to their interface.

How to Deal With Interface Mismatches 

One approach is to use programmable logic devices, such as field-programmable gate arrays (FPGAs), to implement interface bridging and conversion. FPGAs offer high flexibility and can be customized to support various interfaces and formats. However, using FPGAs can lead to high development costs and long design cycles.

Another approach is to use dedicated interface bridging video ICs. Those are optimized for efficiency and reliability in infotainment systems. These purpose-built ICs offer the necessary interface conversion and bridging functions in a single, compact package. These ICs also reduce development costs over FPGA-based solutions.

Interface bridging and conversion are essential for dealing with a diverse range of video formats and interfaces in automotive systems. However, the terms “bridging” and “conversion” refer to two distinct functions:

• Bridging: Selecting one of two video signals to route to a single output, which allows the system to switch between different video sources as needed.
• Conversion: Changing the format of a video signal from one interface standard to another, such as converting from LVDS to MIPI-CSI. The purpose of conversion is to enable compatibility between components with different native interfaces. 

ROHM ML86795 Interface Bridge IC for Automotive Video Applications

To address the evolving needs of automotive IVI systems and simplify integration of disparate video interfaces, ROHM has developed the ML86795 Bridge Interface IC with a comprehensive set of features and benefits for designers to create reliable, and feature-rich IVI systems. 

The ML86795 supports a wide range of video input and output interfaces, including:

• LVDS (single/dual): Up to 160 MHz for single and 80 MHz for dual
• LVTTL: 8-bit, up to 160 MHz
• MIPI CSI-2: 4-lane, up to 1 Gbps per lane

The ML86795 is packaged in a compact 64-pin 0.5-pitch WQFN package, measuring just 9mm x 9mm. This small form factor makes it ideal for space-constrained electronic control units (ECUs) and display modules, allowing designers to create compact and highly integrated IVI systems. 

Key Features and Benefits

A key feature of the ML86795 is its dual-input to single-output switching capability which allows designers to select between two video input sources and route the selected video stream to the desired interface, reducing the need for external switching components and simplifying system design. The ML86795 can handle video resolutions of up to 1920×1080 pixels (Full HD) at frame rates of up to 60 fps, meeting the demands of high-resolution automotive displays and cameras.

ROHM’s ML86795 IC supports conversions between LVDS, LVTTL, and MIPI CSI-2 interfaces, enabling designers to interconnect components with mismatched interface types. This capability eliminates the need for developing new software due to the interface mismatches. In addition to interface conversion, the ML86795 also supports various color formats (RGB and YCbCr) and bit depths, ensuring compatibility with various video sources and display technologies. It also handles both single and dual-link LVDS configurations, accommodating high-bandwidth video transmission for demanding automotive applications.

ML86795 also offers advanced features like virtual channels for efficient video data transmission and processing in infotainment systems. Virtual channel support allows two video streams to be multiplexed over a single MIPI CSI-2 output interface which can then be processed by a single SoC or display controller. This capability reduces the number of physical connections and makes it easier to incorporate multiple video sources into the IVI system. 

ML86795 Bridge Interface IC: Addressing Challenges in IVI Systems 

One of the main challenges in IVI system design is mismatches between the interface formats of camera modules, other video sources, and the SoCs responsible for processing and rendering video content. The ML86795 addresses this challenge by providing conversion between LVDS, LVTTL, and MIPI CSI-2 formats, enabling designers to connect components with different native interfaces without the need for changing to a new SoC or new camera module to use the same interfaces. Moreover, with its broad range of supported video interfaces and formats, the ML86795 offers the flexibility to adapt to various camera and display configurations without extensive hardware modifications. This flexibility enables faster time-to-market, reduces development costs, and simplifies system upgrades and maintenance. 

Key Applications

ROHM’s ML86795 interface bridge IC is a versatile solution that enables automotive designers to create advanced IVI systems with a wide range of features and functionalities, including:

ECU to ECU Connection

An IVI system may consist of multiple ECUs connected together. Each ECU is equipped with a SoC, but in general SoCs often have a MIPI-CSI input interface and an LVDS output interface. When these SoCs are connected to each other, one SoC outputs LVDS and the other SoC inputs MIPI-CSI, resulting in an interface mismatch.The ML86795 can perform LVDS input and MIPI-CSI output. This can solve the interface mismatch between ECU and ECU.

Camera-Based Electronic Mirror Systems 

Electronic mirrors have replaced standard side-view and rearview mirrors with higher-resolution cameras and displays, providing drivers with a clearer, customizable view of their surroundings. These systems are designed to automatically adjust the displayed image based on factors such as lighting conditions, vehicle speed, and drivers’ preferences. In an electronic mirror system powered by the ML86795, the side-view and rearview cameras typically output video streams in either LVDS or MIPI CSI-2 format. ROHM’s ML86795 interface IC can connect cameras to the vehicle’s displays while converting between video interface formats. The ML86795 supports a range of video input and output interfaces, including single/dual LVDS, 8-bit and 16-bit LVTTL, and 4-lane MIPI CSI-2. This versatility allows designers to integrate cameras and displays with different native interfaces without requiring additional conversion components. Its low-latency processing capabilities also minimizes any perceptible delays between inputs and the displayed output, providing a real-time viewing experience for the driver. 

Surround View Systems 

Surround view systems utilize cameras strategically placed around the vehicle (such as front grille, side mirrors, rear bumper, etc.) to generate a bird’s-eye view of the car and its immediate surroundings. The video streams from these cameras are stitched together to create a top-down view of the vehicle’s environment, which helps drivers navigate tight spaces, avoid obstacles, and park with greater ease. In most surround-view systems, each camera outputs a video stream in either LVDS or MIPI CSI-2 format. ROHM’s ML86795 converts these video streams to a common format and combines them with multi-stream and virtual channel support capabilities. Multi-stream support allows it to handle multiple video streams simultaneously, while virtual channel support enables the multiplexing of two video streams over a single MIPI CSI-2 output interface.Moreover, the ML86795’s small package size and low power consumption make it ideal for integration into space-constrained or thermally-sensitive automotive ECUs and camera modules. 

Conclusion

Dedicated interface bridging video ICs are optimized for efficiency and reliability in infotainment systems. By facilitating efficient conversion and routing of video signals, such ICs reduce system complexity, optimize resource usage, and enhance driver and passengers experiences. Offering flexible video interface bridging and conversion capabilities, ROHM’s ML86795 IC eliminates mismatches between cameras, SoC-to-SoC and SoC-SoC interfaces.

For more information on ROHM’s ML86795 interface bridge IC or application-specific inquiries, please visit the ROHM website or contact your local ROHM sales representative.