Overview
ISO 17987-4:2025 - Road vehicles - Local Interconnect Network (LIN) - Part 4: Electrical physical layer (EPL) specification 12 V/24 V defines the electrical physical layer for LIN networks used in automotive systems. It specifies the 12 V and 24 V EPLs used for low-cost single-wire communication between electronic control units (ECUs) with bit rates up to 20 kbit/s. The standard covers electrical characteristics of transmission, basic bus-driver functionality, and physical layer variants for nodes with LIN AA capabilities (procedures C, D and E). All parameters apply across the automotive ambient range of −40 °C to 125 °C.
Key topics and technical requirements
The document addresses practical and testable EPL requirements, including:
- Bit rate deviation and tolerance definitions for BR_Range_20K and BR_Range_10K systems (up to 20 kbit/s).
- Timing requirements: bit timing, synchronization procedures and bit sampling timing for reliable UART-based LIN communication.
- Line driver and receiver specifications: supply voltage definitions, signal specifications and bus-driver basic functionality for both 12 V and 24 V systems.
- Line characteristics and bus capacitance considerations for single-wire networks referenced to ground.
- Performance during fault modes and non-operation supply voltage ranges to ensure robustness in automotive environments.
- ESD/EMI compliance references (normative reference includes IEC 61000-4-2).
- LIN AA procedures C, D, E - normative annexes defining physical layer behaviour for advanced node capabilities.
- Annex A (informative): recommendations for LIN peripheral interface design (UART and frame controller) for both commander and responder nodes.
Practical applications - who uses this standard
ISO 17987-4:2025 is essential for organizations designing, validating or integrating LIN physical layer hardware and systems:
- Automotive ECU hardware and transceiver manufacturers (12 V / 24 V LIN transceivers and bus drivers).
- Vehicle system architects and network integrators implementing LIN clusters for body electronics (doors, HVAC, seats, lighting).
- Embedded firmware and UART peripheral designers implementing LIN commander and responder behaviour.
- Test laboratories and compliance engineers performing conformance testing and EMC/ESD validation.
- Tier-1 suppliers and OEMs specifying LIN EPL requirements for robust in-vehicle communication.
Related standards
- ISO 17987-1: General information and use cases (LIN series overview)
- ISO 17987-2, -3: Transport and logical protocol requirements
- ISO 17987-5: LIN API and node configuration
- ISO 17987-6, -7: Conformance tests and EPL testing
- IEC 61000-4-2: ESD immunity testing
ISO 17987-4:2025 is the authoritative reference for implementing the LIN electrical physical layer (12 V/24 V), ensuring interoperability, durability and predictable behaviour across automotive ECUs and LIN networks.