Electronic-component manufacturers are developing technologies that help the automotive designer achieve these objectives - for example through the deployment of mixed-signal-IC processes in SBCs (system-based chips) targeted at specific applications.. Network requirements The different requirements of various vehicle functions in terms of data rate and the degree to which applications were safety-critical led to the emergence or further development of several standard networks. Networks on a vehicle can be broken into clear groups, each with different needs:- Powertrain (engine and transmission): these are typically low-latency closed-loop control systems with a continuous flow of high amounts of data (typically around 100kbps). They are required to exchange data with other car domains and have a high redundancy requirement.- Chassis (suspension, steering and braking): again, these are low-latency closed-loop control systems that exchange data with other systems in the vehicle. Data flows in long heavy bursts at around 100kbps. Safety is key, so good network reliability and continuity is essential.- Body (comfort functions): although these represent the greatest number of functions in the vehicle, they are the least demanding in terms of network performance. They transport short bursts of slower data, usually triggered by driver and passenger inputs to comfort-function controls. The main demand on body-control networks is that they have flexibility - to accommodate car upgrades for example - and a high degree of compatibility, and are low-cost.- Active and passive safety (airbags, tyre-pressure monitoring, etc.): these networks feature low latency coupled with very high redundancy and safety. Airbags in particular have become widely adopted with the driver's airbag being standard on almost every vehicle. This is now widely being complemented by passenger airbags and complex side-curtain and other airbags in higher specification cars.- Telematics (wireless, navigation, entertainment, diagnostics): this is the noly part of an IVN that is required to exchange data with the external world and therefore must be compatible with non-automotive standards. Latency is not especially important for telematics networks, but these networks have to be able to exchange large amounts of multimedia data both inside and outside the vehicle. Information integrity and confidentiality can both be important.Network protocolsThe primary network protocols that exist to meet the needs of the five application groups are LIN (local interconnect network) and CAN (controller area network). Others used to a lesser extent are MOST (media-orientated systems transport) and FlexRay. Numerous manufacturer-specific protocols also exist. Single-wire LIN is commonly used and has the lowest cost per node. With a data rate of 20kbps (over up to 40m cable) plus good flexibility and extendibility, LIN is well-suited to the body-electronics functions for which it is commonly adopted. Dual-wire CAN is currently the most dominant bus system in the automotive market. It was developed by Bosch in the early 1980s and first used in Mercedes cars in 1992. Although it has the potential to achieve a data rate of 1Mbps (over up to 40m of cable), most current powertrain and chassis systems on which it is prevalent use a 500kbps set-up. MOST uses fibre optics in a point-to-point network with ring, star or daisy-chain topology. Specifically developed to serve rapidly evolving vehicle telematics, audio and multimedia applications, MOST runs at 24Mbps on 64 nodes. As steer-by-wire, brake-by-wire and active safety systems move closer to being adopted for mainstream vehicles, FlexRay is positioned as an ideal network for these types of safety-critical powertrain and chassis applications. Using dual-wire optical fibre, it is able to handle a gross data rate of 500kbps to 10Mbps - significantly higher than CAN, but also much more expensive. Integrated bus interfaceAll IVNs require transceiver functionality to sit between the protocol controller and the physical bus. In order to reduce cost and space requirements and at the same time improve robustness and long-term reliability, it is important that this circuitry be as integrated as possible. Thanks to the advent, in recent years, of mixed-signal processes such as AMI Semiconductor's Smart Power high-voltage, 0.35µm CMOS technology, high-voltage analogue circuitry is now able to co-exist with digital functionality in the same device (Figure 1). Further integration has allowed SBCs to be developed. These incorporate a transceiver, voltage regulator and a host of other features such as a watchdog mode and wake-up circuitry to save power, plus protection through thermal shutdown and ESD measures. SBCs effectively provide a one-chip solution that reduces the number of external components required to just a few de-coupling capacitors. Housed in small SoIC packages, SBCs occupy minimal board space and simplify the design process in what can often be a cramped installation. Add to this the well-proven benefits on reliability of hard-wired connections inside an encapsulated package (as opposed to external ones made on a printed-circuit board), and it’s easy to see why SBCs for IVNs are a key development. As LIN, CAN, FlexRay and MOST installations proliferate down through manufacturers’ vehicle ranges over the coming few years, SBCs, thanks to their ability to combine analogue and digital functions with these standards-based transceivers (Figure 2), will have increasing relevance.