Local Interconnect Networks (LIN) Connect Automotive Gadgets

A local interconnect network (LIN) is a single-wire, bidirectional bus used to link simple devices along a low-speed bus. The protocol was first developed as LIN 1.3 in the late 1990s and has since been moved to ISO 17987 standardization. The LIN protocol describes the physical and data link layers. Standardizing physical connection and data link layers allowed compatibility among multiple devices within automobiles.

The physical arrangement is defined as one master and up to 16 slaves. It is based on ISO 9141 standard with modifications suited to automotive use. Modifications to meet electromagnetic compliance, to protect against electrostatic discharge, and to withstand transient pulse events were customized to the automotive operating environment. Automotive environments withstand greater swings in temperature and are susceptible to greater levels of noise.

The data link layer describes one master communicating with up to 16 slaves. The master communicates by sending serial data identified by a header and one or more strings of bytes. Serial data may form a request to the slave, which request the slave addresses as a response frame. Alternatively, the master may send response data along with an identifying header to which the slave listens.

Background for Automotive Local Interconnect Network

The LIN came about during a time when digital devices were becoming common within the automotive industry. Devices such as door locks, windshield wipers, turning lights, climate control, radio, seat position, cooling fans, and more were in need of low-cost solutions for wiring and communication. From this need, the LIN protocol came about.

Minimizing the number of cables and/or wires necessary to connect multiple devices to the automotive master control unit was needed. LIN was developed to support up to 16 devices, connecting to the same communication wire, along with a bus protocol that arranges data bytes for coherent transmission to microcontrollers for further processing. Using only one wire for 16 devices kept build and material costs contained while adding smart technology to cars.

LINs form clusters that communicate to the MCU

Bus speeds for LIN protocol require no more than 20 kps, and inexpensive clocking schemes are practiced to further keep the design simple yet functional. Developers conceived a configuration protocol that incorporates a LIN description file (LDF) to define specific use and syntax for LIN clusters. Together with the LIN configuration language, a workflow is implemented. With each LIN cluster configured, separate clusters are identifiable for communication with system level buses such as the Controller Area Network commonly found in automobiles.

Parameters to Consider When Selecting a LIN

Local Interconnect Networks are unique to automotive applications. They support many car accessories via one-wire communication channel. Together with a master device, usually a microcontroller, and the LDF configuration files, many devices may be grouped into clusters for information exchange with the master controller. Check to be sure which serial protocol you prefer for upstream communication, as some LIN ICs work with UART while others with SPI.

The following three parts give you options when researching possible parts for system use.

Texas Instruments, TLIN1024-Q1

This is a LIN transceiver supporting up to four connections to a local interconnect network. It is intended for use in automobiles support 12V battery applications. The transmit data rate operates up to 20 kbps, and the part is able to perform across a wide range from 4V to 36V. These ICs contain protection features such as under-voltage protection on the supply, a TXD dominant timeout protection circuit, thermal shutdown, and failsafe at unpowered nodes or ground disconnection.

The TLIN1024-Q1 device is a quad Local Interconnect Network (LIN) physical layer transceiver, which integrates wake up and protection features, compliant to LIN2.0, LIN2.1, LIN2.2, LIN2.2A and ISO/DIS 17987-4.2 standards.

Found on page 1 of TLIN1024-Q1 Quad LIN Transceiver datasheet

This part comes in a small profile QFN package, rated to AECQ100 and qualified for automotive applications. Some applications where this part may find use within an automobile include infotainment and cluster, hybrid electric vehicles and powertrain systems, and for passive safety circuitry.

Microchip, MCP2021/2/1P/2P

This is a LIN transceiver with an included voltage regulator. The part supports baud rates up to 20 kbps (kBaud) with LIN-compatible output driver. It is able to operate across an input supply of between 6V and 18V and may withstand input voltages up to 30V. Its protocol is compatible with an interface to both PIC^® EUSART and standard USART protocols for use with upstream microcontrollers arbitrating system tasks. The part incorporates its own on-chip voltage regulator able to output either 3.3V or 5.0V, depending on system needs.

The MCP2021/2/1P/2P provides a bidirectional, half-duplex communication physical interface to automotive and industrial LIN systems that meet the LIN bus specification Revision 2.1 and SAE J2602-2. The devices incorporate a voltage regulator with 5V at 50mA or 3.3V at 50mA regulated power-supply outputs.

Found on page 2 of MCP2021/2/1P/2P LIN Transceiver with Voltage Regulator datasheet

These parts come in a variety of packaging options, offering versatile design choices, able to support system needs.

ST Microelectronics, L99PM60

This LIN transceiver incorporates power management into overall functionality for device communication. It incorporates 5V low-drop voltage regulators, sourcing up to 100mA of current, in continuous operation. When not in use, leakage reduced to ultra-low 7µA quiescent current. It is compatible with automotive and communicates over an SPI interface for mode control and diagnostics.

The L99PM60J is a power management system IC that features one low-drop regulator, a direct drive for high-side drivers, and a LIN 2.1 compliant SAE J2602 transceiver. The integrated standard serial peripheral interface (SPI) controls all L99PM60J operating modes and provides driver diagnostic functions.

Found on page 8 of L99PM60J Power management IC with LIN transceiver datasheet

This part is available in a PowerSSO-16 package and is intended for use in automobiles. It is particularly suited for communication with automotive ECUs. It’s power management features allow monitoring of specific functional areas of the car.

If you are designing the environment of an automobile to include functional use through the car’s master control unit, a LIN transceiver is a good choice. Low-cost, and with efficient use of cabling and bandwidth, these parts are highly configurable into clusters for clear communication to and from the auto’s master control unit. If you’d like to know more, take a look at our similar parts finder.

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