What are the challenges of electromagnetic compatibility design in automotive electronic circuits?
As engineers develop increasingly complex solutions to meet the needs of comfort, safety, entertainment, powertrain, engine management, stability and control applications, the number of modern in-vehicle electronics will continue to grow steadily. In addition, with the increasing popularity of very sophisticated and sophisticated electronic products in automotive applications, even the most basic types of vehicles are equipped with electronic devices that have been available for a few years ago.
In the past, the growth drivers of automotive electronics were applications that were not related to safety, such as comfort and convenience. Usually, if electric lift windows or central locking are used, these products simply replace the existing mechanical systems. Recently, the scope of automotive electronics has expanded to support security-related applications such as engine optimization, active and passive security systems, and advanced infotainment systems including GPS.
Now, we are welcoming the third revolution in the development of automotive electronics. Automotive electronics no longer only supports critical functions, but also goes deep into the control of the car, providing important driver information, control engines, collision avoidance monitoring and collision avoidance, performing line-controlled braking and steering, or intelligent control of the interior environment. .
Speed and cost are well known issues for general purpose embedded hardware electronic platforms. These platforms have basic or common hardware capabilities and are designed with application-oriented software to customize features for the same model range or for various models in different OEMs. System-on-a-chip (SoC) semiconductor devices integrate various functions into a single chip, reducing the number of components and footprint requirements, while ensuring long-term reliability, while successfully developing a universal embedded electronic platform It is important.
As the number of automotive electronics increases and the distribution of complex electronic modules throughout the vehicle increases, engineers face increasingly severe electromagnetic compatibility design challenges. The problems are mainly in three areas:
1. How to minimize electromagnetic susceptibility (EMS)? To protect electronic products from harmful electromagnetic radiation from other electronic systems such as mobile phones, GPS or infotainment systems.
2. How to protect electronic products from the harsh automotive environment? This includes disturbances caused by large changes in the supply voltage, heavy loads, or inductive loads such as lights and starters.
3. How to minimize the EME that may affect other automotive electronic circuits?
These issues will be even more challenging as system voltages, the number of in-vehicle electronic devices, and the frequency increase. In addition, many electronic modules will interface with inexpensive, less linear, and highly offset low-power sensors that operate in small-signal states, and the effects of electromagnetic interference on their operating conditions can be catastrophic.
Compliance and standards
The above problems indicate that automotive EMC compliance testing has become a major element in automotive design. Standardization of compliance testing has been carried out in car manufacturers, car supplier suppliers and different legislative bodies. However, the later the EMC problem is discovered, the more difficult it is to find the root cause of the EMC problem, the higher the cost of the solution, and the greater the limitations. Because of this, it is the basic design method to consider EMC issues from the whole process of IC design, PCB mass production, module implementation to vehicle design. To facilitate the implementation of this process, module-level pre-compliance testing and IC-level testing have been standardized.
Design EMC-compliant ICs and modules
The following are the EMC standards that IC design should follow:
EME standard IEC 61967: Measurement of radiated and conducted electromagnetic emissions in the 150 kHz to 1 GHz range.
EMS standard IEC 62132: Measurement of electromagnetic immunity (anti-electromagnetic interference) for the 150 kHz to 1 GHz range.
Transient standard ISO 7637: Measurement of conducted and coupled electrical interference caused by road vehicles.
How can a system design engineer ensure that their SoC and final modules meet the requirements of the above standards? The traditional SPICE model (an analog circuit simulator focused on integrated circuit design) does not work here because the electromagnetic field is not compatible with SPICE-based simulation environments. At the IC design level, electromagnetic fields can only be modeled by electric fields because the size of the chip and package is much smaller than the wavelength of the electromagnetic signal (the wavelength of the 1 GHz signal is 30 cm, which is much larger than the size of the IC). The key to note here is that radiated emissions and susceptibility are not major issues with ICs, and effective antennas on printed circuit boards and cables are the main cause of conductive emissions and susceptibility.