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IEC TS 62228: Integrated Circuits — EMC Evaluation of CAN Transceivers
IEC TS 62228 (First Edition, 2007) is a Technical Specification that defines comprehensive test and measurement methods for the electromagnetic compatibility (EMC) evaluation of CAN (Controller Area Network) transceivers. Developed by IEC Subcommittee 47A (Integrated Circuits), this specification is essential for automotive electronics engineers designing CAN-based communication systems where electromagnetic reliability is critical for vehicle safety and performance.
💡 Why CAN Transceiver EMC Matters: In modern vehicles, a single CAN bus may interconnect 20-50 electronic control units (ECUs) from multiple suppliers. A single noisy transceiver can disrupt communications across the entire network, potentially affecting safety-critical functions like braking, steering, and airbag deployment.
1. 📋 Scope and Test Overview
IEC TS 62228 specifies test and measurement methods, test conditions, test setups, test procedures, failure criteria, and test signals for four key EMC characteristics of CAN transceivers:
- RF emissions — narrowband conducted emissions on bus lines measured using the 150 Ω direct coupling method (IEC 61967-4)
- RF immunity — immunity against RF common mode disturbances on signal lines using the Direct Power Injection (DPI) method (IEC 62132-4)
- Transient immunity — immunity against electrical transients (function and damage testing per ISO 7637-2)
- ESD immunity — electrostatic discharge damage immunity (IEC 61000-4-2)
A key feature of the specification is that external protection circuits are NOT applied during testing — ensuring that the results reflect the inherent EMC performance of the transceiver IC itself, not the protection circuitry.
2. 🔬 Test Configurations and Conditions
2.1 Network Configurations
The specification defines two main test configurations:
- Three-transceiver network (powered) — used for RF emission, RF immunity, and transient immunity tests, representing a realistic minimum CAN network
- Single-transceiver test board (unpowered) — used for ESD damage tests on individual pins (bus lines, VBat, wake-up)
| Test | Configuration | Transceiver State | Reference Standard |
|---|---|---|---|
| RF emission | 3-transceiver network | Active (powered) | IEC 61967-4 |
| RF immunity (DPI) | 3-transceiver network | Active (powered) | IEC 62132-4 |
| Transient immunity (function) | 3-transceiver network | Active (powered) | ISO 7637-2 |
| Transient immunity (damage) | 3-transceiver network | Active (powered) | ISO 7637-2 |
| ESD immunity (damage) | Single transceiver board | Passive (unpowered) | IEC 61000-4-2 |
2.2 Communication Test Signals
The specification defines specific test signals (TX1, TX2) that exercise the CAN transceiver under controlled conditions. TX1 is a periodic dominant/recessive bit pattern designed to maximize EMI excitation, while TX2 simulates real-world traffic patterns with mixed frame types. These standardized test signals ensure reproducibility across laboratories.
⚠️ Engineering Critical Point: The minimum network configuration is a critical aspect of the test methodology. Using only three transceivers (instead of a fully populated bus) creates a best-case scenario for signal integrity. In a real vehicle installation with dozens of nodes, signal reflections, loading effects, and crosstalk can significantly degrade EMC performance. Engineers should apply a safety margin of at least 6 dB when using datasheet values obtained from this test configuration.
3. 📊 Detailed Test Methods
3.1 RF Emission Measurement
The 150 Ω direct coupling method measures conducted RF emissions on the CAN_High and CAN_Low bus lines. The measurement uses a decoupling network that presents a defined impedance to the bus while filtering out the DC component and low-frequency communication signals. Emission levels are measured in the frequency domain from 150 kHz to 1 GHz.
3.2 DPI (Direct Power Injection) Immunity
DPI testing evaluates the transceiver’s immunity to RF disturbances by injecting RF power directly into the bus lines, VBat (battery supply), and wake-up lines through coupling networks. The specification defines specific DPI levels, frequency steps, and modulation schemes. During testing, the CAN communication must remain error-free — any CRC error, acknowledge error, or bus-off condition constitutes a failure.
| Test Parameter | Emission Test | DPI Immunity | Transient Test | ESD Test |
|---|---|---|---|---|
| Frequency range | 150 kHz – 1 GHz | 150 kHz – 1 GHz | Pulse width: 0.1 μs – 200 ms | Contact: ±2 to ±8 kV |
| Measurement | Conducted power (dBm) | Forward power (dBm) | Voltage level (V) | Discharge count |
| Coupling | 150 Ω decoupling network | Capacitive (6.8 nF) | Capacitive (100 pF-1 nF) | 150 pF / 330 Ω |
| Failure criteria | Limit line violation | Communication error | Function loss or damage | Pin damage |
✅ Engineering Best Practice: When designing CAN transceivers for high-reliability automotive applications, pay particular attention to the DPI test results at frequencies around 1-100 MHz. This frequency range corresponds to common EMI sources in vehicles (DC-DC converters, ignition noise, switching regulators). A transceiver with poor DPI immunity in this range may exhibit intermittent communication failures that are extremely difficult to diagnose in the field.
4. 🔌 ESD Testing and Protection Design
ESD testing is performed on unpowered devices to evaluate damage immunity. The specification recommends ESD coupling to all relevant pins (CAN_High, CAN_Low, VBat, wake-up) using both contact discharge and air discharge methods. The test severity levels range from ±2 kV to ±8 kV contact discharge, reflecting the automotive environment where ESD events can reach several kilovolts from human handling during assembly or maintenance.
5. ❓ Frequently Asked Questions
Q1: Why does IEC TS 62228 require testing without external protection circuits?
Testing without external protection circuits reveals the intrinsic EMC robustness of the transceiver IC itself. This allows system designers to accurately assess how much additional protection is needed for their specific application environment. If protection circuits were included, the results would be specific to that protection design and not comparable across different transceiver products.
Q2: What is the difference between “function” and “damage” transient tests?
Function tests evaluate whether the transceiver continues to operate correctly during and after a transient disturbance — the device must maintain communication without errors. Damage tests apply higher stress levels to determine the destruction threshold of the IC, helping designers establish absolute maximum ratings and protection requirements.
Q3: How do CAN high-speed and CAN low-speed transceiver tests differ?
The specification provides separate circuit diagrams and test parameters for high-speed (ISO 11898-2) and low-speed (ISO 11898-3) transceivers. High-speed transceivers use differential voltage signaling with faster edge rates, making them more susceptible to common-mode RF disturbances. Low-speed transceivers use single-wire or voltage-referenced signaling. The termination networks and coupling circuits differ accordingly.
