Local Interconnect Network (LIN) Overview and Training


Local Interconnect Network. Today, we’ll discuss the
coexistence of CAN and LIN in automotive networks. We’ll do a brief LIN overview,
discuss the physical layer, and then follow on with
the LIN frame structure, and discuss the key LIN
features to consider when choosing a transceiver. We’ll also discuss the
conformance and EMC test reports that are available
for Texas Instruments LIN transceivers, and discuss
the different package options available. In today’s automobiles,
CAN is the main bus that connects multiple nodes
throughout the vehicle. It’s a differential
two-wire interface. Classic CAN operate up
to 1 megabit per second, and CAN FD operates up
to 5 megabits per second. LIN is a sub-bus. It’s a single-ended,
one-wire interface that communicates at
20 kilobits per second. So what is LIN? LIN stands for Local
Interconnect Network. The core of LIN is a serial
network protocol controller and a physical
layer transceiver. The transceiver transmitter
converts the logic level LIN protocol data stream
on the TXD input into a VBAT level
LIN bus signal using a current-limited, wave-shaping
driver, which reduces electromagnetic emissions. The transceiver receiver
converts the high-voltage data stream from the LIN bus
to logic level signals that are sent to
the microprocessor through the RXD pin. The network protocol controller
provides the synchronization, logic, error detection, and
other features that are usually associated with LIN. The network relies on a
single master communicating with up to 16 slave devices. LIN is a broadcast,
serial, one-wire interface, which is typically implemented
as a sub-bus of a CAN network. It allows automotive
manufacturers to reduce cost by offloading low-speed,
non-safety critical functions from a two-wire CAN
bus to a one-wire bus. One master coordinates
communication between up to 16 slave
devices on the network. The LIN physical layer signals
either recessive or dominant. To indicate dominant, the LIN
pin voltage must be less than or equal to 0.4 of the
system’s supply voltage. It is recessive when
the LIN pin voltage is greater than or equal to 0.6
of the system’s supply voltage. The LIN protocol
specification defines all types of frames that
may be sent on the LIN bus, the fields that make
up each type of frame, and the order of the
bits in each field. The physical layer is unchanged
for LIN specification versions 1.3 through 2.2A. Texas Instruments LIN
devices feature many benefits for customers. They operate off 12 and
24 volt battery systems, providing 45 and 58 volt
bus fault protection; transceiver transmitter,
supporting up to 20 kilobits per second;
transceiver receiver, supporting 100 kilobit
per second data rates to support inline
programming of LIN nodes; multiple node wake
up methodologies; small package options; 8 kV
HBM and IEC 6100-4-2 ESD; dominant estate
time-out support; undervoltage and thermal
shut down; integrated LDOs; as well as watchdogs. Texas Instruments
LIN devices also have conformance and EMC
reports for OEM certification. For conformance, LIN OSI
Layer 1 Physical Layer reports are available, as
well as SAE J2602-2. For EMC, the G5 EMC report,
commonly referred to as the IBEE Zwickau report,
is available as well. The SAE J2962-1 report
is also available. Texas Instruments provides
a full-featured, 8-pin LIN transceiver, using
industry-standard pinout in both SOIC and QFN packages. The full-featured
transceiver, in addition to the LIN transceiver,
has the inhibit and wake pin for system power control
and high-voltage input wake. There is also a reduced
feature 8-pin LIN transceiver in both the SOIC
and QFN package as well. These transceivers do not have
the inhibit and wake pins.