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Advances in auto infotainment systems

Posted: 18 Mar 2014     Print Version  Bookmark and Share

Keywords:infotainment system  GPS  digital audio broadcasting  MOST  SerDes 

There is also a need for encrypted or unencrypted transmission of uncompressed video data with bandwidths of 2Gbps, or more. These transmissions require additional point-to-point connections, usually employing serialisers and deserialisers (SerDes) (figure 3). Here, too, the technology has transitioned from simple, high-speed video transmission to combined methods that support the video and audio signals together with control channels, which in some cases support IP protocols.

It is also not surprising that technologies from the consumer-electronics sector are making their way into automotive electronics. This is where gigabit multimedia serial link (GMSL) technology is so valuable. GMSL devices support audio, video, and control communications and provide a wide range of bandwidths (figure 4). A GMSL SerDes chipset like the MAX9263/MAX9264 and a MAX9266 serialised with LVDS interface are optimised for display applications; the MAX9271/MAX9272 SerDes are optimised for camera applications. GMSL also supports differential or coaxial transmission media that accommodate the special requirements for EMC, ESD, power consumption, and the cost framework.

Figure 3: A modern in-vehicle infotainment system requires multiple point-to-point connections that usually use SerDes chipsets.

High bandwidth at a reasonable price
Recent rapid advancements in computer technology and multimedia applications provide excellent computing power, large memory capacities, high-value display units, and the required data rates at acceptable cost. Not surprisingly, automobile customers also expect their cars to have the same functions and applications that are already in home entertainment, mobile communications, and information technology. Common examples include individual configurations (i.e., personalisation), the integration of cell phones and smartphones, new added capabilities with software apps, and an appealing, state-of-the-art HMI offering high levels of convenience.

As a consequence, automotive-grade versions of the processor and memory products used in consumer electronics are being integrated into cars. The new automotive circuits must support typical interfaces such as USB, HDMI, and MHL, plus wireless technologies such as Bluetooth and Wi-Fi, and wireless energy transmission for charging purposes. While the technologies that have traditionally been employed in automotive and consumer electronics differed greatly in the past, significant technical convergence is evident now.

Figure 4: GMSL link with audio, video, and control communications.

Integration and protection of USB connections in vehicles
The Universal Serial Bus (USB) originally emerged in the 1990s as an interface for connecting disparate end-user devices to a computer. Since then, USB has become a standard interface for mobile communication devices. Now consumers want USB connections for their mobile devices in their vehicles. The expectation is that all smartphone capabilities will remain functional and, of course, the device's battery should be charged by the vehicle's electrical system.

There are significant challenges to making the USB interface usable in automobiles. Both the USB's data lines and its 5V VBUS power supply must be protected against short circuiting to the vehicle ground or to the battery voltage. Moreover, the same levels of ESD protection that are normally provided in a vehicle must be maintained. In accordance with ISO10605, devices like Maxim's MAX16984 achieve 25kV ESD protection (Air-Gap Discharge) for the USB connection.

Integrating the USB interface into a vehicle means that the cable connections from the host processor to the user's USB terminal device become longer. Permanently installed cables with lengths of up to three meters are now common in vehicles. The passengers cable to the smartphone adds to that length. Today's mobile devices require charging currents of up to 2A. Because of the ohmic losses in the cables, it is necessary to compensate for the voltage drop caused by the cables used when such high charging currents are employed. This compensation can be accomplished with a load-dependent increase in the VBUS voltage.

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