LIN as the last kilometer network becomes the best solution

When someone says "local network," you might think of the Internet , local area network (LAN) , Wi-Fi®, or Ethernet . Although these technologies are robust and wide-ranging, both wireless transceivers for Wi-Fi and protocols that support the enabling of applications on the Internet require high fees.

Highly integrated systems like cars need to support networks that require low overhead to easily route in the limited space in the car. With a large number of power nodes throughout, reducing the cost of each node is also crucial.

Specifically, if Wi-Fi networks are enabled on all the control units of a car, it means placing a radio transmitter/receiver on each node; not only is it expensive, but the antenna on the circuit board can be quite large. If Ethernet is enabled, there may not be a radio transceiver at each node, but it requires at least four wires to implement the physical layer - four wires can simultaneously send low-speed engine control unit (ECU) data and high-speed video data. In the trade-off between speed and overhead, two-wire controller area network (CAN) and single-wire local interconnect network (LIN) have been developed.

Designers favor high speed CAN (>5Mbps) and robustness against transmission failures. LIN is more like a single-wire ground return (SWER) transmission line used to bring the Internet to rural communities. To access the Internet, these rural households must be connected to the main network; however, distance and wiring costs to support these families make the traditional transmission line economically infeasible. In Figure 1, you can see that a SWER power line uses a wire to connect a remote home to the Internet. The construction of the SWER transmission line covers all remote areas. This is why LIN is called the “last mile network” because in the car, LIN can connect the remotely located node to the main network via a single line.

Figure 1: SWER transmission line connects rural communities to the network through a single line

Typical settings inside the car include a microcontroller with a CAN/LIN gateway . The CAN can pass the message to the microcontroller, which passes the messages along the LIN bus to the remote node. Figure 2 depicts this process, which shows how the radar system communicates with the seat motor via LIN. For many modules in a car, LIN is their only contact with the network. Table 1 lists the implementation differences between CAN and LIN.

Figure 2: This figure shows the car's radar network's message through LIN to the remote seat motor

Table 1: Implementation differences between CAN and LIN

As you can see, introducing CAN into remote nodes is a very difficult task that may increase the cost and complexity of the project. This is why LIN is the best solution for the last mile. Integrated LIN transceivers such as TI's TLIN1029-Q1 and TLIN2029-Q1 enable you to take full advantage of LIN's low-cost network connections for all 12V and 24V applications.