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IEC 62228-1: EMC Evaluation of CAN Transceivers – General Conditions and Definitions
Integrated Circuits – EMC Evaluation of Transceivers for Controller Area Network (CAN)
EMC Testing Framework for CAN Transceivers
IEC 62228-1 (first edition, 2018) establishes the general conditions and definitions for electromagnetic compatibility (EMC) evaluation of integrated circuit transceivers used in Controller Area Network (CAN) systems. As CAN buses have become ubiquitous in automotive, industrial automation, and building control applications, the need for standardised EMC characterisation of the physical-layer transceiver ICs has become critical. This standard provides a common reference for both IC manufacturers and system integrators, enabling consistent comparison of EMC performance across different transceiver designs from various suppliers.
CAN transceivers operate in electrically harsh environments — adjacent to ignition systems, motor drives, and switching power converters. A transceiver that passes IEC 62228-1 EMC requirements is significantly more likely to achieve system-level EMC compliance without costly additional filtering or shielding.
The standard covers two fundamental aspects of EMC evaluation: electromagnetic emission (the unintentional RF energy generated by the transceiver during normal operation) and RF immunity (the transceiver’s ability to maintain correct bus communication when subjected to external electromagnetic interference). Key parameters defined include:
| Parameter | Specification | Test Condition |
|---|---|---|
| Supply voltage (VCC) | 5 V ± 10% | Normal operation |
| CAN bus voltage (Vbus) | Per ISO 11898-2/3 | Recessive/dominant levels |
| Bit rate | 125 kbit/s, 250 kbit/s, 500 kbit/s, 1 Mbit/s | Configurable per test requirement |
| Termination resistance | 60 Ω (two 120 Ω differential) | Per CAN standard |
| Common-mode choke | As per manufacturer recommendation | Optional; to be stated in test report |
| Temperature range | -40 °C to +125 °C (automotive grade) | Device junction temperature |
A crucial measurement detail: the standard specifies that emission measurements be performed with the transceiver driven by a pseudo-random bit sequence (PRBS-9 or PRBS-15) to represent realistic bus traffic. Using a simple periodic pattern can underestimate emission levels by up to 10 dB compared to PRBS excitation.
The ICP/IEC 62228 series extends beyond Part 1 (general conditions) to cover specific transceiver types in later parts: Part 2 for CAN, Part 3 for LIN, Part 4 for FlexRay, and Part 5 for Ethernet. Each part references the general definitions and test board specifications established in Part 1 while adding technology-specific test conditions. The standardised test board design (including PCB stack-up, connector placement, decoupling capacitor layout, and bus termination) ensures reproducibility across different test laboratories.
Test Methods and Performance Criteria
Emission testing under IEC 62228-1 employs the IEC 61967 family of measurement methods for integrated circuits, specifically the TEM/GTEM cell method (IEC 61967-2) and the surface scan method (IEC 61967-3). For conducted emissions, the 1 Ω/150 Ω direct coupling method (IEC 61967-4) measures RF currents on the supply and bus pins. The frequency range typically spans 150 kHz to 1 GHz for radiated measurements, with conducted measurements extending from 150 kHz to 230 MHz. Limits are specified in peak and quasi-peak detector modes to correlate with both narrowband and broadband interference sources.
Design engineers must pay particular attention to the decoupling network on the test board. The standard defines specific decoupling capacitor values (10 nF + 100 nF + 4.7 μF) and PCB layout rules to ensure that measured emissions originate from the transceiver rather than from resonances in the power delivery network. An improperly decoupled test board can produce measurement variations exceeding 6 dB between laboratories.
Immunity testing follows IEC 62132 methodology. The bulk current injection (BCI) method (IEC 62132-3) is the primary technique, injecting RF current from 1 MHz to 400 MHz (extensible to 1 GHz) directly onto the CAN bus cables via a current injection probe. The transceiver must maintain correct CAN communication without bit errors exceeding the specified criteria, typically defined as no more than one error frame per 106 transmitted bits at an RF level of 100 mA (or 200 mA for extended automotive requirements). The DPI (direct power injection) method (IEC 62132-4) complements BCI by evaluating immunity at the IC pin level, injecting RF power through a coupling capacitor into the supply and bus pins while monitoring for communication degradation.
| Test Method | Standard Reference | Frequency Range | Measurement |
|---|---|---|---|
| TEM/GTEM Cell | IEC 61967-2 | 150 kHz – 1 GHz | Radiated emission (electric field) |
| Surface Scan | IEC 61967-3 | 1 MHz – 1 GHz | Magnetic near-field mapping |
| 1 Ω/150 Ω Method | IEC 61967-4 | 150 kHz – 230 MHz | Conducted emission (RF current) |
| Bulk Current Injection (BCI) | IEC 62132-3 | 1 MHz – 400 MHz | RF immunity (cable level) |
| Direct Power Injection (DPI) | IEC 62132-4 | 150 kHz – 1 GHz | RF immunity (pin level) |
A well-designed CAN transceiver meeting IEC 62228-1 Class III (highest performance level) typically achieves 20 dB higher immunity and 10 dB lower emissions compared to a minimally compliant Class I device. For safety-critical automotive applications (e.g., brake-by-wire, steer-by-wire), Class III devices are strongly recommended despite their higher cost.
The standard also defines three performance classes for both emission and immunity. Class I represents basic compliance, suitable for non-critical applications with moderate EMC requirements. Class II targets general-purpose automotive and industrial applications. Class III is reserved for high-performance transceivers intended for safety-critical or severe electromagnetic environments. The test report must clearly state the achieved class, test configuration (including any external components such as common-mode chokes or bus termination variations), and the specific pass/fail criteria applied.
From a system design perspective, achieving EMC compliance at the transceiver level through IEC 62228-1 yields significant benefits at the ECU (electronic control unit) and vehicle level. A transceiver with well-characterised emission and immunity profiles simplifies PCB layout by reducing the need for additional filtering components, saves bill-of-materials cost, and shortens the EMC debugging phase during product development. Many automotive OEMs now specify minimum IEC 62228-1 performance classes in their component technical specifications, making this standard a de facto requirement for suppliers targeting the automotive market. For industrial applications, compliance with IEC 62228-1 Class II is typically sufficient for most factory automation and building control scenarios.
Frequently Asked Questions
Q1: What is the difference between IEC 62228-1 and the ISO 11898 series?
ISO 11898 defines the CAN protocol, physical layer signalling, and bus topology requirements. IEC 62228-1 specifically addresses the EMC characterisation of the transceiver IC that implements the physical layer. Both standards are complementary: a CAN design requires ISO 11898 compliance for bus communication and IEC 62228-1 compliance for EMC performance.
ISO 11898 defines the CAN protocol, physical layer signalling, and bus topology requirements. IEC 62228-1 specifically addresses the EMC characterisation of the transceiver IC that implements the physical layer. Both standards are complementary: a CAN design requires ISO 11898 compliance for bus communication and IEC 62228-1 compliance for EMC performance.
Q2: Does the standard cover CAN FD (Flexible Data-Rate)?
CAN FD operation is enabled by the same physical-layer transceivers as classical CAN. While IEC 62228-1 does not yet have CAN FD-specific provisions, the test methodology applies equally; the key difference is that CAN FD requires higher bit rates (up to 5 Mbit/s in the data phase), which may affect emission and immunity behaviour at higher frequencies.
CAN FD operation is enabled by the same physical-layer transceivers as classical CAN. While IEC 62228-1 does not yet have CAN FD-specific provisions, the test methodology applies equally; the key difference is that CAN FD requires higher bit rates (up to 5 Mbit/s in the data phase), which may affect emission and immunity behaviour at higher frequencies.
Q3: How does the choice of common-mode choke affect EMC test results?
The common-mode choke is one of the most influential external components. A choke with higher common-mode impedance (typically ≥ 2 kΩ at 10 MHz) can improve immunity by 10-15 dB and reduce conducted emissions by 5-10 dB. However, the choke adds cost and PCB area, so its use should be justified by the target EMC class and application environment.
The common-mode choke is one of the most influential external components. A choke with higher common-mode impedance (typically ≥ 2 kΩ at 10 MHz) can improve immunity by 10-15 dB and reduce conducted emissions by 5-10 dB. However, the choke adds cost and PCB area, so its use should be justified by the target EMC class and application environment.
Q4: Are IEC 62228-1 tests required for certification in automotive applications?
While not mandated by law, most automotive OEMs require IEC 62228-1 compliance as part of their component EMC specifications. Passing this standard significantly streamlines vehicle-level EMC homologation per UN ECE Regulation 10 (R10).
While not mandated by law, most automotive OEMs require IEC 62228-1 compliance as part of their component EMC specifications. Passing this standard significantly streamlines vehicle-level EMC homologation per UN ECE Regulation 10 (R10).
