In more than ten years, our research on electromagnetic shielding materials (conductive cloth, conductive foam, etc.) has become increasingly sophisticated. When it comes to electromagnetic shielding, their synonymous words EMI (electromagnetic interference) and EMC (electromagnetic compatibility) make us not Don't mention it. Let us start from the back and explain the concept of EMC (Electromagnetic Compatibility) first.
When the company recently did a car project for BYD, it found that the number of electronic devices in modern bicycles is constantly increasing, and the standards for electromagnetic compatibility of products are becoming more and more stringent. The higher and higher integration of products has led to an increase in integrated circuit solutions. This article makes a series of discussions and explorations on the electromagnetic compatibility and integrated circuit problems faced by designers.
More than ten years ago, the pursuit of comfort and convenience gave us a deeper pursuit of electronic products, so that electromagnetic shielding and electromagnetic compatibility have become the basis for the evolution of electronic products, and it has also contributed to the pursuit of electromagnetic compatibility and electromagnetic shielding solutions. . Recently, the scope of automotive electronic equipment has expanded to support some keyword applications, such as engine optimization, active and passive safety systems, and advanced infotainment systems including global positioning systems.
In the current era of automotive electronics, electronic equipment not only supports key functions, but also shifts to control key functions, such as intelligent driving, intelligent detection, prevention and other fields. Following the trend of the times and the development of many electronic fields, it is not difficult for us to find that these applications require electronic solutions with lower cost, easy installation, stable performance and higher and higher intelligence.
Factors such as speed and cost contributed to the birth of a "universal" embedded hardware electronic platform. These platforms can provide basic or common hardware functions, and can customize different functions according to the requirements of different car manufacturers. System-on-chip semiconductor solutions integrate multiple functions into one integrated circuit, which can reduce the number of components and space requirements, while ensuring long-term reliability, which is extremely important for the development of a successful general-purpose embedded electronic platform.
With the continuous increase of automotive electronic equipment and the increasing application of complex electronic modules in various parts of the car, the issue of electromagnetic compatibility has increasingly become a design challenge faced by engineers. The three main issues are:
(a) How to minimize electromagnetic sensitivity so that electronic devices are not affected by electromagnetic emissions from other electronic systems such as mobile phones, global positioning systems, or infotainment equipment.
(b) How to protect electronic equipment from the harsh automotive environment, including transients in the power supply system and interference when switching lights and starting motors and other large loads or inductive loads.
(c) How to minimize electromagnetic emissions that can affect other automotive electronic circuits.
Moreover, with the increase of system voltage, the increase of vehicle electronic equipment and the frequency increase caused by more high-frequency electronic equipment, these problems have become more and more challenging. In addition, many electronic modules now also interface with low-power, inexpensive sensors with poor linearity and large zero offsets. These sensors rely on small signals, and electromagnetic interference will be catastrophic for their normal operation.
Compatibility testing, pre-compatibility testing and standards
These problems mean that automotive electromagnetic compatibility testing has become a basic element of automotive design. Compatibility testing has been standardized among car manufacturers, their suppliers and various legislative bodies. The later an electromagnetic compatibility problem is discovered, the harder it is to identify its root cause, and the solution may be more limited and expensive. Therefore, it is a basic approach to consider electromagnetic compatibility issues at all stages of the process-from integrated circuit design and printed circuit board layout to module installation and final car layout design. In order to simplify this process, pre-compatibility testing that considers electromagnetic compatibility issues at the module and integrated circuit stage has been standardized.
The latest semiconductor technology
Many designers are using mixed-signal semiconductor technology to provide the system-on-chip solutions required by today's automotive applications. The latest high-voltage mixed signal technology is particularly suitable for designs that require high-voltage output — such as driving motors or starting relays — and is combined with analog signal condition functions and complex digital processing.
The I2T and I3T series developed by AMIS are examples of the latest high-voltage mixed-signal application specific integrated circuit technology. I3T80 is based on a 0.35 micron CMOS process and can handle a maximum voltage of 80 volts, so that complex digital circuits, embedded microprocessors, memory, peripherals, high-voltage functions and various interfaces can be integrated in an integrated circuit.
Several functions are integrated in I3T80 single chip
Figure 1 illustrates several functions integrated in a single chip manufactured using I3T80 technology, including sensor analog interface (one of the most common requirements for automotive applications), high-voltage drivers for motors and transmissions, and the use of embedded 16/32-bit ARM ( tm) The digital processing circuit of the processor core. For low-power processing needs, an 8-bit embedded R8051 processor is also provided. As shown in the figure, other'standard' IP modules that AMIS can provide include timers, pulse width modulation (PWM) functions, JTAG to simplify device testing, interfaces, and communication transceivers that include CAN bus and LIN bus communication options. Finally, it should be pointed out that I3T technology contains built-in protection functions to protect the application specific integrated circuit from damage due to overvoltage or incorrect battery connection.
AMIS mixed signal technology
AMIS uses this mixed-signal technology and many electromagnetic compatibility reasonable design methods described in this article to develop various application-specific standard products (ASSP) for the automotive industry, including AMIS-41682 standard speed, AMIS-42665 and AMIS-30660 high-speed CAN transceiver. These devices provide an interface between the CAN controller and the physical bus, simplifying the design and reducing the number of components in 12V and 24V cars and industrial applications that require CAN communication at a maximum rate of 1 Mbaud. For example, AMIS-30660 fully complies with the ISO 11898-2 standard, and provides differential signaling capabilities for the CAN bus through the transmitting and receiving pins of the CAN controller. The integrated circuit provides designers with a choice of 3.3 volt or 5 volt logic level interfaces to ensure compatibility with existing applications and the latest low-voltage designs. The carefully matched output signal minimizes electromagnetic emissions, eliminating the need for common mode chokes; and the large common mode voltage range (±35 volts) input to the receiver ensures high electromagnetic sensitivity (EMS). Figure 2 shows the electromagnetic immunity performance comparison of AMIS-30660 and other competitive products.
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