Automotive electronics system EMC design challenges

With engineers develop increasingly sophisticated solutions to meet the comfort, the demand for security, entertainment, powertrain, engine management, stability, and control applications, the number of modern automotive electronics products will continue to grow steadily. In addition, with very sophisticated electronic products in automotive applications gaining popularity, even the most basic type of vehicle is also equipped with a few years ago has been a high-end cars have electronic equipment.

In the past, growth in automotive power electronics is unrelated to security applications and other comfort and convenience. Typically, such as the use of electric lift windows or central locking, these products simply replace existing mechanical systems. Recently, automotive electronics categories have been expanded to support safety-related applications, such as engine optimization, active and passive safety systems and advanced infotainment systems include GPS including.

Now, we are to meet the third revolution in automotive electronics development. Automotive electronics is no longer just support key functions, and deep into the car under control, provide important driver information, control engine, monitoring and collision avoidance collision avoidance, brakes and steering-by-wire execution or implementation of intelligent control car environment .

For universal electronic embedded hardware platforms, speed and cost issues are well known. These platforms have basic or common hardware features through application-oriented software design can be tailored functionality for various models of the same or a different model series depot. System-on-chip (SoC) semiconductor devices to a variety of functions into a single chip, reducing the component count and footprint requirements, to ensure long-term reliability at the same time, for the successful development of general embedded electronic platform is to crucial.

Electromagnetic Compatibility

With the increase in the number of automotive electronics and complex electronic modules increase distribution throughout the vehicle, engineers face increasingly severe EMC design challenges, problems mainly in three aspects:

1. How electromagnetic susceptibility (EMS) is reduced to a minimum? To protect electronic products from the effects of other electronic systems (such as mobiles phoness, GPS or infotainment system) harmful electromagnetic radiation.

2. How to protect the electronics from the harsh automotive environment impact? Including the power supply voltage is large instantaneous changes in load or interference caused by heavy inductive loads (such as lights and starter).

3. How will likely have an impact on other automotive electronic control circuits EME minimum?

As the system voltage, the number of vehicle electronic device and the frequency increases, these problems will be more challenging. In addition, many electronic module with an inexpensive, low linearity, offset a large low-power sensor interface, these sensors work in small-signal state, the effects of electromagnetic interference on the status of their work could be disastrous.

Compliance and standards

These problems show that automotive EMC compliance testing has become a major element of car design. Standardized conformance testing has been carried out at the depot, the depot supporting suppliers and different legislative groups. However, the more EMC problems discovered late, find the root of the problem more difficult EMC, the higher the cost of the solution will be, subject to the limitations likely to be. Because of this, from IC design, PCB production, the whole process of implementation of the module to the vehicle's design to proceed to consider EMC problems will be the basic design. In order to facilitate the implementation of this process, module-level pre-compliance testing and IC-level testing has been standardized.

EMC-compliant IC design and modules

Here is the EMC standard IC design should follow:

EME standard IEC 61967: for 150kHz to 1GHz range radiated and conducted electromagnetic emission measurements.

EMS standard IEC 62132: 150kHz to 1GHz range for electromagnetic immunity (resistance to electromagnetic interference) measurements.

Transient standard ISO 7637: Electrical disturbance by conduction and coupling for road vehicles due measurements.

How does the system designer to ensure that its SoC modules meet the above criteria and final request? Traditional SPICE model (with a focus on IC design analog circuit simulator) in this matter, because the electromagnetic field is not compatible with SPICE-based simulation environment . In the IC design level, the electromagnetic field of an electric field can be modeled as, chip and package size than the wavelength of the electromagnetic signal is much smaller (1GHz signal wavelength is 30cm, much larger than the size of the IC). The key here is to be noted that the main problem is not radiated emission and susceptibility of IC, a printed circuit board and the effective antenna cable is causing major problems conduction emission and susceptibility and other reasons.

Design engineer to take a number of techniques to ensure EMC compliance, the following sequence study EME and EMS.

EM emission

EME (electromagnetic emissions) by the antenna-like outer loop frequency current generated by such a high frequency current comprising:

- Core digital logic switches, such as DSP and clock drivers (synchronous logic generates contains many high-frequency components of a large number of current spikes);

- Operation of analog circuits;