ISO 17987-4:2025

International
Standard
ISO 17987-4
Second edition
Road vehicles — Local Interconnect
2025-06
Network (LIN) —
Part 4:
Electrical physical layer (EPL)
specification 12 V/24 V
Véhicules routiers — Réseau Internet local (LIN) —
Partie 4: Spécification de la couche électrique physique (EPL)
12V/24V
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions .1
3.2 Symbols .2
3.3 Abbreviated terms .5
4 Conventions . 6
5 Electrical physical layer requirements . 6
5.1 Bit rate deviation .6
5.1.1 General .6
5.1.2 12 V LIN systems: parameters .6
5.1.3 24 V LIN systems: parameters .7
5.2 Timing requirements .9
5.2.1 Bit timing .9
5.2.2 Synchronization procedure .9
5.2.3 Bit sample timing .10
5.3 Line driver/receiver . 12
5.3.1 General configuration . 12
5.3.2 Definition of supply voltages for the physical interface . 12
5.3.3 Signal specification . 13
5.3.4 12 V LIN systems: electrical parameters .14
5.3.5 24 V LIN systems: Electrical parameters .18
5.3.6 Line characteristics .21
5.3.7 12 V LIN systems: performance in non-operation supply voltage range . 22
5.3.8 24 V LIN systems: performance in non-operation supply voltage range . 22
5.3.9 Performance during fault modes . 22
5.3.10 ESD/EMI compliance . 22
6 Procedures C, D and E . .23
Annex A (informative) LIN peripheral interface design considerations.24
Annex B (normative) LIN AA procedure C physical layer .29
Annex C (normative) LIN AA procedure D physical layer .32
Annex D (normative) LIN AA procedure E physical layer .39
Bibliography .43

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 31, Data
communication.
This second edition cancels and replaces the first edition (ISO 17987-4:2016), which has been technically
revised.
The main changes are as follows:
— master and slave terms used for the LIN node types in the ISO 17987 series are replaced within this
document with inclusive language terms commander and responder. This also applies for abbreviations
and file formats NCF and LDF;
— variables and formulae aligned with the ISO/IEC Directives, Part 2;
— updates of several parameter statements and requirements;
— various parameter values adopted in Annex C;
— editorial updates and several statements improved to avoid ambiguities.
A list of all parts in the ISO 17987 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The LIN protocol as proposed is an automotive focused low speed universal asynchronous receiver
transmitter (UART) based network. Some of the key characteristics of the LIN protocol are signal-based
communication, schedule table-based frame transfer, commander/responder communication with error
detection, node configuration and diagnostic service transportation.
The LIN protocol is for low-cost automotive control applications as, for example, door module and air
conditioning systems. It serves as a communication infrastructure for low-speed control applications in
vehicles by providing:
— signal-based communication to exchange information between applications in different nodes;
— bit rate support from 1 kbit/s to 20 kbit/s;
— deterministic schedule table-based frame communication;
— network management that wakes up and puts the LIN cluster into sleep state in a controlled manner;
— status management that provides error handling and error signalling;
— transport layer that allows large amount of data to be transported (such as diagnostic services);
— specification of how to handle diagnostic services;
— electrical physical layer specifications;
— node description language describing properties of responder nodes;
— network description file describing behaviour of communication;
— application programming interface.
The ISO 17987 series is based on the open systems interconnection (OSI) basic reference model as specified
in ISO/IEC 7498-1 which structures communication systems into seven layers.
The OSI model structures data communication into seven layers called (top down) application layer (layer 7),
presentation layer, session layer, transport layer, network layer, data link layer and physical layer (layer 1). A
subset of these layers is used in the ISO 17987 series.
The ISO 17987 series distinguishes between the services provided by a layer to the layer above it and the
protocol used by the layer to send a message between the peer entities of that layer. The reason for this
distinction is to make the services, especially the application layer services and the transport layer services,
reusable also for other types of networks than LIN. In this way, the protocol is hidden from the service user
and it is possible to change the protocol if special system requirements demand it.
The ISO 17987 series provides all documents and references required to support the implementation of the
requirements related to the following.
— ISO 17987-1: provides an overview of the ISO 17987 series and structure along with the use case
definitions and a common set of resources (definitions, references) for use by all subsequent parts.
— ISO 17987-2: specifies the requirements related to the transport protocol and the network layer
requirements to transport the PDU of a message between LIN nodes.
— ISO 17987-3: specifies the requirements for implementations of the LIN protocol on the logical level of
abstraction. Hardware-related properties are hidden in the defined constraints.
— ISO 17987-4 (this document): specifies the requirements for implementations of active hardware
components which are necessary to interconnect the protocol implementation.

v
— ISO/TR 17987-5: specifies the LIN application programming interface (API) and the node configuration
and identification services. The node configuration and identification services are specified in the API
and define how a responder node is configured and how a responder node uses the identification service.
— ISO 17987-6: specifies tests to check the conformance of the LIN protocol implementation according
to ISO 17987-2 and ISO 17987-3. This comprises tests for the data link layer, the network layer and the
transport layer.
— ISO 17987-7: specifies tests to check the conformance of the LIN electrical physical layer implementation
(logical level of abstraction) according to this document.

vi
International Standard ISO 17987-4:2025(en)
Road vehicles — Local Interconnect Network (LIN) —
Part 4:
Electrical physical layer (EPL) specification 12 V/24 V
1 Scope
This document specifies the 12 V and 24 V electrical physical layers (EPL) of the LIN communications system.
The electrical physical layer for LIN is designed for low-cost networks with bit rates up to 20 kbit/s to connect
automotive electronic control units (ECUs). The medium that is used is a single wire for each receiver and
transmitter with reference to ground.
Annex A provides recommendations on the LIN physical layer peripheral interface design of type UART and
frame controller for commander and responder nodes.
This document includes the definition of electrical characteristics of the transmission itself and also the
documentation of basic functionality for bus driver devices.
This document also provides the physical layer definitions for nodes with LIN AA capabilities according to
one of the procedures C, D and E.
All parameters in this document are defined for the ambient temperature range from −40 °C to 125 °C.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 17987-1, Road vehicles — Local Interconnect Network (LIN) — Part 1: General information and use case
definition
IEC 61000-4-2, Electromagnetic compatibility (EMC) — Part 4-2: Testing and measurement techniques —
Electrostatic discharge immunity test
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions given in ISO 17987-1 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
BR_Range_20K
LIN systems which operate at speeds up to 20 kbit/s

3.1.2
BR_Range_20K 12 V
12 V LIN systems which operate at speeds up to 20 kbit/s
3.1.3
BR_Range_20K 24 V
24 V LIN systems which operate at speeds up to 20 kbit/s
3.1.4
BR_Range_10K
LIN systems which operate at speeds up to 10,417 kbit/s
3.1.5
BR_Range_10K 12 V
12 V LIN systems which operate at speeds up to 10,417 kbit/s
3.1.6
BR_Range_10K 24 V
24 V LIN systems which operate at speeds up to 10,417 kbit/s
3.2 Symbols
C' line capacitance
LINE
C total bus capacitance
BUS
C capacitance of commander node
COMMANDER
C RXD capacitance (LIN receiver, RXD capacitive load condition)
RXD
C capacitance of responder node
RESPONDER
2 2 2 2
d V/dt second derivative of voltage (volt per second )
di/dt instantaneous rate of current change (amps per second)
D reverse battery supply protection diode
Rev_Batt
D serial internal diode at transceiver IC
ser_int
D serial commander diode
ser_commander
F commander bit rate deviation from nominal bit rate
TOL_RES_COMMANDER
F commander bit rate deviation from nominal bit rate in BR_Range_20K systems
TOL_RES_COMMANDER_A
F commander bit rate deviation from nominal bit rate in BR_Range_10K systems
TOL_RES_COMMANDER_B
F responder bit rate deviation from nominal bit rate
TOL_RES_RESPONDER
F responder bit rate deviation from nominal bit rate in BR_Range_20K systems
TOL_RES_RESPONDER_A
F responder bit rate deviation from nominal bit rate in BR_Range_10K systems
TOL_RES_RESPONDER_B
F responder node 1 bit rate deviation from nominal bit rate
TOL_RES_RESPONDER_1
F responder node 2 bit rate deviation from nominal bit rate
TOL_RES_RESPONDER_2
F responder node to responder node bit rate deviation
TOL_RESPONDER_to_RESPONDER
F responder node bit rate deviation from commander node bit rate after synchro-
TOL_SYNCH
nization
F responder node bit rate deviation from commander node bit rate after synchro-
TOL_SYNCH_A
nization in BR_Range_20K systems
F responder node bit rate deviation from commander node bit rate after synchro-
TOL_SYNCH_B
nization in BR_Range_10K systems
F deviation of synchronized responder bit rate to the commander node bit rate
TOL_SYNCH_BDM
F responder node 1 bit rate deviation from commander node bit rate after syn-
TOL_SYNCH_1
chronization
F responder node 2 bit rate deviation from commander node bit rate after syn-
TOL_SYNCH_2
chronization
F responder node bit rate deviation from nominal bit rate before synchronization
TOL_UNSYNCH
F responder node bit rate deviation from nominal bit rate before synchronization
TOL_UNSYNCH_A
in BR_Range_20K systems
F responder node bit rate deviation from nominal bit rate before synchronization
TOL_UNSYNCH_B
in BR_Range_10K systems
I current into the ECU bus line
BUS
I current limitation for driver dominant state driver on V = V into ECU
BUS_LIM BUS BAT_max
bus line
I current at ECU bus line when V is disconnected
BUS_NO_BAT BAT
I current at ECU bus line when V is disconnected
BUS_NO_GND GND_ECU
I current at ECU bus line when driver off (passive) at dominant LIN bus level
BUS_PAS_dom
I current at ECU bus line when driver off (passive) at recessive LIN bus level
BUS_PAS_rec
GND GND of ECU
Device
l total length of LIN bus line
BUS
LIN LIN network
Bus
R total bus-resistor including all responder node and commander node resistors
BUS
R = R ||R ||R || to ||R
BUS COMMANDER RESPONDER_1 RESPONDER_2 RESPONDER_N
R commander resistor with default range
COMMANDER
R pull-up resistor
pull_up
R responder resistor
RESPONDER
R precise responder resistor with small range
RESPONDER_SMALL
t byte field synchronization time
BFS
t basic bit times
BIT
t earliest bit sample time
EBS
t latest bit sample time
LBS
t propagation delay of receiver
rx_pd
t symmetry of receiver propagation delay rising edge propagation delay of receiver
rx_sym
t propagation delay time of receiving node at falling (recessive to dominant) LIN
rx_pdf
bus edge
t propagation delay time of receiving node at rising (dominant to recessive) LIN
rx_pdr
bus edge
t sample window repetition time
SR
V maximum dominant threshold of receiving node (volt)
TH_dom(max)
V minimum dominant threshold of receiving node (volt)
TH_dom(min)
V maximum recessive threshold of receiving node (volt)
TH_rec(max)
V minimum recessive threshold of receiving node (volt)
TH_rec(min)
V voltage at the anode of the diode
ANODE
V voltage across the ECU supply connectors
BAT
V voltage across the vehicle battery connectors
BATTERY
V voltage on the LIN bus
BUS
V centre point of receiver threshold
BUS_CNT
V receiver recessive voltage
BUS_rec
V voltage at the cathode of the diode
CATHODE
V battery ground voltage
GND_BATTERY
V voltage on the local ECU ground connector with respect to vehicle battery ground
GND_ECU
connector (V )
GND_BATTERY
V receiver hysteresis voltage
HYS
V recessive voltage
Rec
V voltage drop at the serial diodes
SerDiode
V battery shift
Shift_BAT
V difference between battery shift and GND shift
Shift_Difference
V GND shift
Shift_GND
V voltage at transceiver supply pins
SUP
V voltage which the device is not destroyed; no guarantee of correct operation
SUP_NON_OP
V receiver threshold voltage of the recessive to dominant LIN bus edge
th_dom
V receiver threshold voltage of the dominant to recessive LIN bus edge
th_rec
ΔF/F deviation of node bit rate from the commander node bit rate
COMMANDER
ΔF/F deviation from nominal bit rate
Nom
τ time constant
3.3 Abbreviated terms
AC alternate current
API application programming interface
ASIC application specific integrated circuit
BFS byte field synchronization
DC direct current
EBS earliest bit sample
ECU electronic control unit
EMC electromagnetic compatibility
EMI electromagnetic interference
EPL electrical physical layer
ESD electrostatic discharge
EVT event
GND ground
LBS latest bit sample
Max. maximum
Min. minimum
OSI open systems interconnection
Param parameter
RC RC time constant τ (τ = C × R )
BUS BUS
RX Rx pin of the transceiver
RXD receive data
SR sample window repetition
TRX transceiver
Tx Tx pin of the transceiver
TXD transmit data
Typ. typical
UART universal asynchronous receiver transmitter

4 Conventions
The ISO 17987 series and ISO 14229-7 are based on the conventions specified in the OSI service conventions
(see ISO/IEC 10731) as they apply for physical layer, protocol, network and transport protocol and diagnostic
services.
5 Electrical physical layer requirements
5.1 Bit rate deviation
5.1.1 General
The bit rate deviation of the LIN medium describes the bit rate deviation from a referenced bit rate. It is the
sum of the following parameters:
— inaccuracy of setting the bit rate (systematic failure due to granularity of the configurable bit rate);
— clock deviation over temperature and supply voltage range;
— clock source stability of the responder node starting from the end of the sync byte field up to the end of
the entire LIN frame (last sampled bit) when performing synchronization;
— bit time measurement failure of the responder node;
— clock source stability of the commander node starting from the end of the sync byte field up to the end of
the entire LIN frame (last transmitted bit).
On-chip clock may achieve a frequency deviation of better than ±14 % with internal calibration. This bit
rate deviation better than ±14 % is sufficient to detect a break field in the message stream. The subsequent
bit rate adaptation using the sync byte field ensures the proper reception and transmission of the message.
The on-chip oscillator shall allow for accurate bit rate measurement and generation for the remainder of the
message frame, taking into account effects of anything, which affects the bit rate, such as temperature and
voltage drift during operation.
The bit rates on the LIN bus are specified in the range of 1 kbit/s to 20 kbit/s. The specific bit rate used on a
LIN bus is defined as the nominal bit rate, F .
Nom
In case a non-LIN electrical physical layer (e.g. CAN physical medium attachment (PMA) as specified in
ISO 11898-2) is used, the bit rate can be adjusted.
5.1.2 12 V LIN systems: parameters
Table 1 defines the bit rate deviation from nominal bit rate.
Table 1 — Bit rate deviation from nominal bit rate
Number Bit rate deviation Name ΔF/F
Nom
Param 1 Commander node (deviation from nominal bit rate) F <±0,5 %
TOL_RES_COMMANDER
Param 2 Responder node without making use of synchronization (deviation F <±1,5 %
TOL_RES_RESPONDER
from nominal bit rate)
Param 3 Initial deviation of responder node bit rate from the nominal bit rate F <±14 %
TOL_UNSYNCH
according to 5.2.2.1.
This is required for a reliable break field detection to enter synchroni-
zation procedure.
Table 2 defines the responder node bit rate deviation from commander node bit rate.

Table 2 — Responder node bit rate deviation from commander node bit rate
Number Bit rate deviation Name ΔF/F
COMMANDER
Param 4 Deviation of responder node bit rate from the commander node bit F <±2 %
TOL_SYNCH
rate after synchronization; it is relevant for nodes making use of syn-
chronization. Any responder node shall stay within this deviation for
all fields of a frame which follow the sync byte field.
Table 3 defines the bit rate deviation for responder to responder communication.
Table 3 — Bit rate deviation for responder to responder communication
Number Bit rate deviation Name ΔF/F
COMMANDER
Param 5 For communication between any two nodes (i.e. data stream from one F <±2 %
TOL_RESPOND-
responder to another responder), their bit rate shall not differ by more
ER_to_RESPOND-
than F . The condition shall be checked for:
TOL_RESPONDER_to_RESPONDER ER
a)  |F − F | < F
TOL_RES_RESPONDER_1 TOL_RES_RESPONDER_2 TOL_RESPONDER_to_RE-
;
SPONDER
b)  |F − F | < F ;
TOL_SYNCH_1 TOL_SYNCH_2 TOL_RESPONDER_to_RESPONDER
c)  |(F + F ) − F |
TOL_RES_COMMANDER TOL_SYNCH_1 TOL_RES_RESPONDER_2
< F .
TOL_RESPONDER_to_RESPONDER
5.1.3 24 V LIN systems: parameters
The required accuracy is dependent on the used bit rate range. See Table 15 and ISO 17987-2.
Table 4 defines the bit rate deviation from nominal bit rate in BR_Range_20K systems.
Table 4 — Bit rate deviation from nominal bit rate in BR_Range_20K systems
Number BR_Range_20K bit rate deviation Name ΔF/F
Nom
Param 39 Commander node deviation from nominal bit rate. F
TOL_RES_
<±0,3 %
The nominal bit rate F is defined in the LDF or NCF.
Nom COMMANDER_A
Param 40 Responder node without making use of synchronization (deviation
from nominal bit rate) F
TOL_RES_RESPOND-
<±0,3 %
For communication between any two nodes, their bit rate shall not
ER_A
differ by more than ±0,6 %.
Param 41 Deviation of responder node bit rate from the nominal bit rate
before synchronization; it is relevant for nodes making use of F <±14 %
TOL_UNSYNCH_A
synchronization and direct break field detection.
Table 5 defines the bit rate deviation for responder nodes from commander node in BR_Range_20K systems.

Table 5 — Bit rate deviation for responder nodes from commander node in BR_Range_20K systems
Number BR_Range_20K bit rate deviation Name ΔF/F
COMMANDER
Param 42 Deviation of responder node bit rate from the commander node bit
rate after synchronization; it is relevant for nodes making
use of synchronization. Any responder node shall stay within F <±0,6 %
TOL_SYNCH_A
this deviation for all fields of a frame which follow the sync byte
field.
Param 43 For communication between any two nodes (i.e. data stream from
one responder to another responder), their bit rate shall not differ
by more than F . The condition shall be
TOL_RESPONDER_to_RESPONDER
checked for:
F
TOL_RESPOND-
a)  |F − F | < F
TOL_RES_RESPONDER_1 TOL_RES_RESPONDER_2 TOL_RESPOND- <±0,6 %
ER_to_RESPONDER
;
ER_to_RESPONDER
b)  |F − F | < F ;
TOL_SYNCH_1 TOL_SYNCH_2 TOL_RESPONDER_to_RESPONDER
c)  |(F + F )− F |
TOL_RES_COMMANDER_A TOL_SYNCH_1 TOL_RES_RESPONDER_2
< F .
TOL_RESPONDER_to_RESPONDER
Table 6 defines the bit rate deviation from nominal bit rate in BR_Range_10K systems.
Table 6 — Bit rate deviation from nominal bit rate in BR_Range_10K systems
Number BR_Range_10K bit rate deviation Name ΔF/F
Nom
Param 44 Commander node deviation from nominal bit rate. F
TOL_RES_
<±0,5 %
The nominal bit rate F is defined in the LDF or NCF.
Nom COMMANDER_B
Param 45 Responder node without making use of synchronization (devia-
tion from nominal bit rate) F
TOL_RES_RESPOND-
<±1,5 %
For communication between any two nodes, their bit rate shall
ER_B
not differ by more than ±2,0 %.
Param 46 Deviation of responder node bit rate from the nominal bit rate
before synchronization; it is relevant for nodes making use of F <±14 %
TOL_UNSYNCH_B
synchronization and direct break field detection.
Table 7 defines the bit rate deviation for responder nodes from commander node in BR_Range_10K systems.
Table 7 — Bit rate deviation for responder nodes from commander node in BR_Range_10K systems
Number BR_Range_10K bit rate deviation Name ΔF/F
COMMANDER
Param 47 Deviation of responder node bit rate from the commander node
bit rate after synchronization; it is relevant for nodes making
use of synchronization. Any responder node shall stay within F <±2,0 %
TOL_SYNCH_B
this deviation for all fields of a frame which follow the sync byte
field.
Param 48 For communication between any two nodes (i.e. data stream
from one responder to another responder), their bit rate shall not
differ by more than F . The following
TOL_RESPONDER_to_RESPONDER
conditions shall be checked for:
a)  |F − F | < F
F
TOL_RES_RESPONDER_1 TOL_RES_RESPONDER_2 TOL_RESPOND-
TOL_RESPOND-
<±2,0 %
;
ER_to_RESPONDER
ER_to_RESPONDER
b)  |F − F | < F :
TOL_SYNCH_1 TOL_SYNCH_2 TOL_RESPONDER_to_RESPONDER
c)  |(F + F ) − F
TOL_RES_COMMANDER_B TOL_SYNCH_1 TOL_RES_RESPOND-
|
ER_2
< F .
TOL_RESPONDER_to_RESPONDER
5.2 Timing requirements
5.2.1 Bit timing
If not otherwise stated, all bit times in this document use the bit timing of the commander node as a reference.
5.2.2 Synchronization procedure
The sync byte field is a byte field with fixed value 55 . It is transmitted as part of the header by the
commander node following the initial sync break field.
The commander node shall detect a mismatch between read back and sent data in the sync byte field (see
ISO 17987-3:2025, 5.4.2) and cancel the PID field transmission.
Responder nodes receive the sync break and sync byte field sequence and shall verify their validity before
accepting the PID field. In case of a failed verification the responder node waits for the next sequence.
Sync field processing in the responder node shall either be performed:
— as byte field reception (see ISO 17987-3:2025, 5.2.2.2) and validation against fixed value 55 or
— as a measurement between falling edges of the pattern (bit rate measurement range). The falling edges are
expected to be available in distances of 2 bit, 4 bit, 6 bit and 8 bit times. Validation of the received pattern
shall be performed on the measured 2-bit sequences or with equivalent measures (see ISO 17987-6:2025,
PT-CT 9).
Measured 2-bit sequences allow a calculation of the commander node bit time, t .
BIT
Effects like timer quantisation or physical layer voltage drifts shall be considered in the 2-bit sequence
measurement value comparison with a certain acceptance margin. A margin of ±1/4 t which can be
BIT
derived from the first measured 2-bit sequence is recommended.
Figure 1 shows the sync byte field and measurement range.
Figure 1 — Sync byte field
Responder nodes performing sync field measurement may offer one or both of the following options.

5.2.2.1 Bit rate synchronization option
The responder node synchronizes its bit rate to the commander node, called bit rate synchronization. This
is done to compensate an inaccurate oscillator (including temperature and/or voltage drift) used in the
responder node according to parameters 3, 41, 46.
— Synchronization shall be performed with every header received.
— Adapted bit rate shall be effective before the PID reception starts.
— Adapted bit rate shall achieve a deviation smaller than parameter 4/parameter 48 (including
measurement, calculation and configuration fault).
— If the measured bit rate is outside the expected range of the nominal bit rate the responder node shall
not synchronize to this bit rate (robustness) and shall not process the current header but shall wait for
the next sync break field. A maximum deviation to the nominal bit rate according to parameters 3, 41, 46
applies.
5.2.2.2 Bit rate detection option
The responder node detects and adapts to multiple network bit rates, called bit rate detection.
— Network bit rate detection and adaptation shall be performed each time after powering up when
communication starts.
— Latest the third frame header after powering up shall be handled correctly and with adapted bit rate.
NOTE Due to responder node bit rate adaptation over a wide bit range (init at a high bit rate and detected a
slow bit rate) it is possible that the frame used for initial bit rate detection is not received correctly.
— Measurement may stop after adaption to the detected network bit rate.
— Recommended validation: detected bit rate corresponds to expected bit rate (pre-configured in the
responder node); a frame with valid checksum byte is received.
It is recommended to consider two potentially lost frames at the beginning of communication in the
network design.
5.2.3 Bit sample timing
The bits of a byte field shall be sampled according to the following specification. In Figure 2, the bit sample
timing of a byte field is illustrated. The corresponding timing parameters are listed in Table 8.
A byte field shall be synchronized at the falling edge of the start bit. The byte field synchronization (BFS)
shall have an accuracy of t .
BFS
All methods for start bit sampling that met the byte field synchronization t are allowed.
BFS
After the byte field synchronization on the falling edge of the start bit, the data bit itself shall be sampled
within the window between the earliest bit sample (EBS) time, t , and the latest bit sample (LBS) time,
EBS
t . The latest bit sample time, t , depends on the accuracy of the byte field synchronization, t . The
LBS LBS BFS
dependency between t and t is given in Formula (1):
LBS BFS
t = 10/16 t − t (1)
LBS BIT BFS
The following bits shall be sampled within the same range as the sample window of the first data bit with
the sample window repetition time, t , respectively. The sample window repetition time, t , is specified
SR SR
from the EBS of the former bit (n-1) to the EBS of the current bit; see Formula (2):
t = t − t = t − t = t (2)
SR EBS(n) EBS(n-1) LBS(n) LBS(n-1) BIT

Table 8 — Bit sample timing
Number Parameter Min. Typ. Max. Unit Comment/condition
Param 6 t — 1/16 2/16 t Value of accuracy of the byte field detection
BFS BIT
Param 7 t 7/16 — — t Earliest bit sample time, t ≤ t
EBS BIT EBS LBS
Param 8 t — — — t Latest bit sample [see Formula (1)], t ≥ t
LBS BIT LBS EBS
For devices that make use of more than one sample per bit, the bit sample majority shall determine the bit
data. Furthermore, the sample majority shall be between the EBS and the LBS.
Table 9 defines the bit sample timing example.
Table 9 — Bit sample timing example
UART/SCI
t t t = 10/16 t − t
BFS EBS LBS BIT BFS
cycles per t
BIT
16 1/16 t 7/16 t 9/16 t
BIT BIT BIT
8 1/8 t (= 2/16 t ) 4/8 t (= 8/16 t ) 4/8 t (= 8/16 t )
BIT BIT BIT BIT BIT BIT
Figure 2 shows the bit sample timing.
Figure 2 — Bit sample timing
5.3 Line driver/receiver
5.3.1 General configuration
The bus line driver/receiver is based on ISO 9141. It consists of the bidirectional bus line LIN which
is connected to the driver/receiver of every bus node, and is connected via a termination resistor and a
diode to the positive transceiver supply voltage, V (see Figure 3). The diode is mandatory to prevent an
SUP
uncontrolled power supply of the ECU from the bus in case of a “loss of battery”.
It is important to note that the LIN specification refers to the voltages at the external electrical connections
of the electronic control unit (ECU), and not to ECU internal voltages. In particular, the parasitic voltage
drops of reverse polarity diodes shall be considered when designing a LIN transceiver circuit.
5.3.2 Definition of supply voltages for the physical interface
V denotes the supply voltage at the connector of the ECU. Electronic components within the unit may
BAT
see an internal supply V being different from V (see Figure 3). This can be the result of protection
SUP BAT
filter elements and dynamic voltage changes on the bus. This shall be taken into consideration for the
implementation of semiconductor products for LIN.
Figure 3 — Difference between external supply voltage, V , and the internal supply voltage, V
BAT SUP
5.3.3 Signal specification
Figure 4 shows the voltage levels on the bus line.
Figure 4 — Voltage levels on the bus line
For a correct transmission and reception of a bit, it shall be asserted that the signal is available with the
correct voltage level (dominant or recessive) at the bit sampling time of the receiver. Ground shifts as well as
drops in the supply voltage shall be taken into consideration as well as symmetry failures in the propagation
delay. Figure 5 shows the timing parameters that impact the behaviour of the LIN bus. The minimum and
maximum values of the different parameters are listed in the following tables.
Key
1 LIN bus signal
Figure 5 — Definition of bus timing parameters
The propagation delay of a receiver starts at the receiver threshold and ends on the edge of the RXD pin.
Figure 6 shows how the propagation delay is defined. In Figure 6 the threshold range for recessive to dominant
and dominant to recessive based on the parameters 19 and 20 (V and V ) are demonstrated too.
BUS_CNT HYS
Figure 6 — Description of the receiver propagation delay and the receiver propagation delay
symmetry.
5.3.4 12 V LIN systems: electrical parameters
5.3.4.1 DC parameters
The electrical DC parameters of the LIN electrical physical layer and the termination resistors are listed
in Tables 10 and 11, respectively. Unless otherwise specified, all voltages are referenced to the local ECU
ground and positive currents flow into the ECU.
In case of an integrated resistor/diode network, no parasitic current paths shall be formed between the bus
line and the ECU-internal supply (V ), for example by ESD elements.
SUP
Table 10 defines the electrical DC parameters of the LIN electrical physical layer.

Table 10 — Electrical DC parameters of the LIN electrical physical layer
Number Parameter Min. Typ. Max. Unit Comment/condition
a
Param 9 V 8 — 18 V ECU normal supply operating voltage range
BAT
i
Param 92 V 6,5 — 8 V ECU low supply operation voltage range
BAT_low
b
Param 10 V 7 — 18 V Normal supply operating voltage range
SUP
j
Param 93 V 5,5 — 7 V Low supply operating voltage range
SUP_low
Param 11 V −0,3 — 40 V Voltage range within which the device is not
SUP_NON_OP
destroyed; no guarantee of correct operation
c
Param 12 I 40 — 200 mA Current limitation for driver dominant state
BUS_LIM
d
driver on V = V
BUS BAT_max
Param 13 I −1 — — mA Input leakage current at the receiver
BUS_PAS_dom
including pull-up resistor as specified in
Table 11 parameter 26 driver off
V = 0 V
BUS
V = 12 V
BAT
Param 14 I — — 20 µA Driver off
BUS_PAS_rec
8 V < V < 18 V
BAT
8 V < V < 18 V
BUS
V ≥ V
BUS BAT
Param 15 I −1 — 1 mA Control unit disconnected from ground
BUS_NO_GND
GND = V
Device SUP
0 V < V < 18 V
BUS
V = 12 V
BAT
Loss of local ground shall not affect
communication in the residual network.
Param 16 I — — 100 µA V disconnected
BUS_NO_BAT BAT
V = GND
SUP
0 < V < 18 V
BUS
Node shall sustain the current that can flow
under this condition. Bus shall remain opera-
tional under this condition.
Param 17 V — — 0,4 V Receiver dominant state
BUS_dom SUP
Param 18 V 0,6 — — V Receiver recessive state
BUS_rec SUP
e
Param 19 V 0,475 0,5 0,525 V V = (V + V )/2
BUS_CNT SUP BUS_CNT th_dom th_rec
Param 20 V — — 0,175 V V = V − V
HYS SUP HYS th_rec th_dom
a
V denotes the supply voltage at the connector of the control unit and may be different from the internal supply, V , for
BAT SUP
electronic components (see 5.3.2).
b
V denotes the supply voltage at the transceiver inside the control unit and may be different from the external supply, V ,
SUP BAT
for control units (see 5.3.2).
c
I is the current flowing into the node.
BUS
d
A transceiver shall be capable to sink at least 40 mA. The maximum current flowing into the node shall not exceed 200 mA
under DC conditions to avoid possible damage.
e
V is the receiver threshold of the recessive to dominant LIN bus edge. V is the receiver threshold of the dominant to
th_dom th_rec
recessive LIN bus edge.
f
V is the voltage at the anode of the diode. V is the voltage at the cathode of the diode.
ANODE CATHODE
g
V is the voltage across the vehicle battery connectors. V is the voltage on the local ECU ground connector with
BATTERY GND_ECU
respect to vehicle battery ground connector (V ).
GND_BATTERY
h
This constraint refers to duty cycle D and D only.
1 2
i
Optional parameter in addition to parameter 9.
j
Optional parameter in addition to parameter 10.
k
This constraint refers to duty cycle D and D only.
3 4
TTaabblle 1e 10 0 ((ccoonnttiinnueuedd))
Number Parameter Min. Typ. Max. Unit Comment/condition
Param 21 V 0,4 0,7 1,0 V Voltage drop at the serial diodes
SerDiode
D , D and D in pull-up
ser_commander ser_int Rev_Batt
path (Figure 3)
f
V = V − V
SerDiode ANODE CATHODE
h
Param 22 V 0 — 11,5 % V Battery shift
Shift_BAT BAT
g
k
V = V − V − V
V 0 — 11,1 % V
...