Electromagnetic Compatibility for Electric Vehicles

IEC 61000-4-4 (Electric Fast Transients / Burst)

A burst arc occurs when a mechanical contact is open during the switching process. Burst sources:
• Circuit Breakers in electrical circuits
• High Voltage switchgear
• 110/230V Power Supply systems
• 24V Control Lines

A burst has a single pulse rise time/duration of 5 ns / 50 ns from a 50 Ohm source impedance.
Bursts of 15 ms duration with a repetition rate of 5 kHz (or 100 kHz) are applied every 300 ms.

Voltage test levels:
• Power ports: 0.5 KV, 1 KV, 2 KV, 4 kV
• Signal and Control ports: 0.25 KV, 0.5 KV, 1 KV, 2 kV

• Coupling method is used to transfer the transient to the DUT.
• Decoupling method is used to block the transient from entering the mains and damaging other equipment connected in the network.

• Power line coupling is done with direct CDNs (Coupling/Decoupling Networks).
• Signal line coupling is done with a CCC (Capacitive Coupling Clamp): two metal plates which sandwich the line under test (cable) to provide a distributed coupling capacitance.

Test waveform verification is mandatory prior to each test.
For equipment connected to power ports all lines are coupled simultaneously.

Christian Rosu

Electromagnetic Spectrum

Spectrum is a continuum of all electromagnetic waves (EM) traveling at constant speed (300,000 km/s). An electromagnetic wave consists of electric and magnetic fields which vibrates thus making waves. EM wave wavelength decreases as its frequency increases. Shorter the wavelength, higher is the EM wave energy. Waves with higher frequency can carry a higher energy. The energy is measured in Joules or Electron-Volt (1 J = 6.241509 *10^18 eV).

Wave speed is independent of frequency. Frequency has an inverse relationship to the wavelength, λ (lambda). Lambda * Frequency = Speed

Frequency Allocation Charts:

US: 2011_US_rf_spectrum_chart.pdf (334.3KB)

CANADA: 2014_Canadian_Radio_Spectrum_Chart.pdf (279.1KB)

UK: uk_frequency_allocations_chart.pdf (325.8KB)

AUSTRALIA: aust_rf_spectrum_allocations_chart.pdf (296.7KB)

Automotive Cold Crank, Load Dump, and Reverse Polarity Protection

The suppliers of automotive electronic devices are competing these days to lower the cost of theirs designs. This is a sample of rather expensive solution to ensure proper function of an automotive electronic device during transients on supply lines (12V Battery).

Sample of less expensive solution to prevent reverse polarity, load dump, and cranking pulse from disturbing circuits sourced from a 5V voltage regulator or directly from the 12V B+ line.

Automotive 12V Battery - Voltage Drops

Simple simulation to prevent voltage drop issues for 9V to 16V operating voltage range devices.

All DUT's functions are required to perform as designed during battery voltage drops of up to 1 ms.  For drops above 1 ms the functions are allowed to be temporarily disrupted or fail in a safe mode. Upon return to the operating voltage range the DUT is supposed to auto-recover and resume its operation. In the above example the DUT's functions should not be disrupted (dropout = 1.3 ms, B+ = 9.36 V).

In the above example (dropout = 1.67 ms, B+ = 8.65 V) a fail safe behavior is acceptable. The software will prevent the DUT from resuming its operation as long as B+ is detected below the voltage range. Once B+ line is above 9V the auto recover process should be initiated.

Automotive Cranking Pulse

The Cold Cranking Pulse occurs when starting the engine in the morning and even worse in cold weather. Controllers supporting CAN bus will be notified that a temporary low battery voltage condition will occur. Motion controllers modules (e.g. power lift gate) driving in that moment electrical motors will have to stop the ongoing operation and store their current status (e.g. lift gate position and direction) just before the Cold Cranking Pulse occurs. Once the Battery voltage returns to nominal (e.g. 12.8 V) the motion controller should safely resume its operation.

CAN Bus Higher Layer Implementations

As the CAN standard does not include tasks of application layer protocols, such as flow control, device addressing, and transportation of data blocks larger than one message, and above all, application data, many implementations of higher layer protocols were created. Several are standardized for a business area, although all can be extended by each manufacturer. For passenger cars, each manufacturer has its own standard. Among these implementations are:

• ARINC 825 (for the aviation industry)

• CANaerospace (for the aviation industry)

• CAN Kingdom

• CANopen (used for industrial automation)


• DeviceNet (used for industrial automation)

• EnergyBus (used for electrical vehicles)

• GMLAN (for General Motors)

• ISO 15765-4

• ISO 11783 or ISOBUS (agriculture)

• ISO 14229

• SAE J1939 (heavy road vehicles)

• ISO 11992 for heavy trailers

• MilCAN

CAN bus 10

• NMEA 2000 (marine industry)

• RV-C (used for recreational vehicles)

• SafetyBUS p (used for industrial automation)

• SmartCraft

• Smart Distributed System (SDS)

• VSCP (used for building automation)

Christian Rosu

CAN Bus Standards

There are several CAN physical layer and other standards:

ISO 11898-1: CAN Data Link Layer and Physical Signaling

ISO 11898-2: CAN High-Speed Medium Access Unit

ISO 11898-2 uses a two-wire balanced signaling scheme. It is the most used physical layer in car

Powertrain applications and industrial control networks.

ISO 11898-3: CAN Low-Speed, Fault-Tolerant, Medium-Dependent Interface

ISO 11898-4: CAN Time-Triggered Communication

ISO 11898-4 standard defines the time-triggered communication on CAN (TTCAN). It is based on the

CAN data link layer protocol providing a system clock for the scheduling of messages.

ISO 11898-5: CAN High-Speed Medium Access Unit with Low-Power Mode

ISO 11898-6: CAN High-speed medium access unit with selective wake-up functionality

ISO 11992-1: CAN fault-tolerant for truck/trailer communication

ISO 11783-2: 250 kbit/s, Agricultural Standard

ISO 11783-2 uses four unshielded twisted wires; two for CAN and two for terminating bias circuit

(TBC) power and ground. This bus is used on agricultural tractors. This bus is intended to provide

interconnectivity with any implementation adhering to the standard.

ISO 15765-2 also called ISO-TP, is a standard for flow control and handling of messages larger than eight bytes.

SAE J1939-11: 250 Kbit/s, Shielded Twisted Pair (STP)

SAE J1939-15: 250 Kbit/s, Unshielded Twisted Pair (UTP) (reduced layer)

The SAE J1939 standard uses a two-wire twisted pair, −11 has a shield around the pair while −15 does not. SAE 1939 defines also application data and is widely used in heavy-duty (truck) and autobus industry as well as in agricultural & construction equipment.

SAE = Society of Automotive Engineers; NMEA = National Marine Educators Association; SDS = Smart Distributed System