Electronics & Connectivity - November 28, 2012 - 7

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Networks are doorway for new features and functions
The Local Interconnect Network (LIN) is one of the enablers for the many functions now found in doors. As the low-cost link continues to lower the complexity of wiring to expand its role by simplifying usage, designers are coming up with new ways to improve network efficiency. The inexpensive low-speed network is helping design teams cram more functions into doors while also aiding in the drive to trim weight and boost fuel economy. Networking also lets designers put controls further away from the modules they manage. “As more applications are being put on the LIN bus, the amount of wiring in the door is reduced even though new applications such as ambient lighting are increasing the number of LIN nodes in the door,” said David Schellenberger, Americas Marketing Manager at Microchip Technology’s Automotive Products Group. “Functions such as power seat controls that were previously located on the seat can easily be placed on the door panel to give the occupants better access.” Engineers note that LIN makes it possible to put more functions in tight spaces and reduce the weight of wiring. Side mirrors are a case in point. The network only requires three wires, so it’s easy to cram sensors, LEDs with controllers, and multiple motors into a side mirror. “If the load is centrally controlled, there are more than 20 wires required, which can generate big trouble in the mirror joint,” said Manuel Gärtner, Technical Marketing Engineer for STMicroelectronics Automotive Group. “Controlling the mirror with LIN minimizes the number of wires by a factor of seven, to only the ground, power, and data lines of LIN.” Chipmakers are doing more to help automakers implement LIN. For example, NXP Semiconductors makes controllers that are easy to configure when various versions of a door have different numbers of nodes. “Self-learning LIN nodes learn where on the bus they are,” said Lars Reger, Vice President of Automotive Strategy for NXP. “If you’ve got 30 nodes in a door,

LIN is helping fuel a dramatic increase in a broad range of comparatively simple electronic functions. (Microchip)
that saves a lot of time.” System engineers have also devised techniques that can trim overall power consumption. The CAN networks that manage LIN nodes will often shut down little-used areas such as seat and door sub networks. This scheme is called partial networking. “To save current and fuel, new idle modes are implemented,” Gärtner said. “The connection of front doors with the body controller will be done by a CAN physical layer with partial networking capability.” While LIN has become the dominant link inside doors, it doesn’t have the performance to meet the needs of safety systems. Airbags in doors usually have their own connections. “If there’s an airbag in the door, it needs to trigger in a millisecond, so it will typically use dedicated wiring,” Reger said. Terry Costlow

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November 28, 2012

Electronics & Connectivity - November 28, 2012

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