The increasing importance of electronic products in automobiles has led to the increasing demand for low-cost and high reliability sensors and transmission devices. These devices do not exist independently, but must communicate with the main electronic control unit (ECU) of the system. In the past, sensor / transmission communication usually used one-way analog signal, and each remote device used its own special line to connect with ECU. Because the automotive environment is full of electrical noise, it is difficult to maintain signal integrity on these lines, and the reliability of the system will be affected. Cabling can cause other problems – occupying space, increasing weight and cost, and difficult to maintain. Fortunately, digital multiplex communication technology can solve the above problems. This technology can maintain signal integrity, reduce the number of lines required, and provide a new opportunity to realize the intelligent control of the whole vehicle.

Today’s two major trends – Automotive communication bus standardization and semiconductor technology are promoting the development of more intelligent sensors and transmission devices. At the same time, they also expand the application field of automotive electronic systems through efficient communication. The local area Internet (Lin) bus architecture has been developed to version 2.0, which can meet the needs of simple communication schemes for sensors / actuators, reduce costs and improve robustness through standardization。 The advent of Lin standard also caters to the development of mixed signal semiconductor process technology. Together, they can realize all the typical functions required for connecting sensors and drives to a single integrated circuit (IC). Moreover, Lin standard and advanced mixed signal technology also bring opportunities for automobile manufacturers to introduce low-cost, new electronic systems and reduce the cost of existing systems. While bringing high convenience and safety to car owners, they can also improve maintenance performance and reliability.

Step back and ask for the second

In the current automotive electronic bus standard, Lin can provide the best solution to meet the signal transmission requirements of sensors and transmission devices. There are a variety of proprietary solutions for digital transmission of signals through simple schemes such as pulse width modulation (PWM) or adjustable pulse width (VPW). These schemes are based on various physical layer (PHY) designs. In these schemes, each sensor or transmission device generally needs a communication line, and the communication from sensor to ECU or ECU to transmission device generally adopts one-way output. Therefore, these network architectures can not realize two-way communication and diagnosis, which limits their use. In addition, because they are proprietary solutions, they affect the industry to achieve economies of scale and design reuse through the implementation of open standards.

The alternative is to adopt mature communication standards (such as control area network (can) bus) to transmit signals between the sensor / transmission interface and ECU. However, can and similar communications generally require the use of microcontrollers and auxiliary circuits, resulting in complexity and cost beyond the required range or reasonable range of sensors and drives. In addition, can is also based on two-wire bus, and the best solution only needs to use one line to realize low-speed and low-cost communication.

Simple open standards

Although the initial design goal of Lin is vehicle body electronics, it is also useful in new applications, one of which is the sensor / transmission interface. The 20.0kbps data rate specified by Lin 2.0 is sufficient to meet the needs of most sensors and drives, and Lin phy and protocol controller can be easily integrated into mixed signal integrated circuits for remote devices. The Lin 2.0 specification contains the protocol definitions describing the physical layer and the data link layer; In addition, the specification also includes a configuration language description for defining system configuration and general interfaces between network nodes, which can also be used as input data for development and analysis tools; It also contains application programming interface (API) definitions for additional software. As a standard specially defined by Lin Alliance for automotive applications, this standard can realize seamless development and design tool chain, and improve the development speed and reliability of the network.

Lin is a single wire transmission mode, which can reduce the requirements of wiring and harness, thus helping to reduce weight and save space and cost. This standard specifies that a single master node has 16 independent slave nodes. The communication is triggered by the master node as planned, so there is no need to perform optimization between simultaneous reporting devices. The slave node has self synchronization characteristics, and the on-chip RC oscillator can be used instead of crystal or ceramic resonator, so as to greatly reduce the cost. Lin protocol can ensure the delay of signal transmission and realize the predictability of the system – this is the key element of most sensor / transmission signals. The protocol is extremely simple and can be run through asynchronous serial port (UART / SCI). Therefore, the implementation cost of the chip is very low, making Lin an excellent bus solution for mixed signal technology – which is mainly used to produce signal conditioning and output IC used in automotive sensors and transmission devices.

Realize mixed signal process

Lin standard is an important progress in automotive sensor / transmission communication. However, its importance is more prominent after it is integrated with the latest development of mixed signal semiconductor technology. Now, because they can make full use of their expertise in high-speed CMOS digital technology and advanced analog technology, IC manufacturers can achieve the system integration level that was Tianfang night lake a few years ago. Typical advanced mixed signal processes for automotive sensor / transmission applications include linear Bi CMOS (LBC), high voltage CMOS, and insulating silicon (SOI) processes. Many of the above processes can realize the implementation of the whole sensor / drive electronic system on chip (SOC), including power supply, high voltage, digital logic, storage and high-precision analog functions.

If intelligence is required on the chip, advanced mixed signal technology allows a reasonable level of digital logic to be integrated outside the Lin protocol controller. For example, the design may include logic devices that can report the status of sensors or drives so that the diagnostic function can be used for both timely maintenance and lifelong reliability database development. The next generation of mixed signal technology will allow the microcontroller to operate δ Yellow babbler? Umbrella 4 Dead howl? Low Minister? What pregnant music τ Magnesium chips? Knocking on the gully? Relief# 8220; Point touch window regulator – it needs to run an algorithm to prevent crushing fingers when the glass rises. For applications requiring more complex and faster communication, the semiconductor function of Lin communication integration also allows the integration of can function in mixed signal devices.

Examples of sensors / Drives

Tpic1021 lin-2.0 transceiver of Texas Instruments (TI) is the cornerstone of using advanced mixed signal integration technology to improve the robustness of Lin compatible sensor and transmission communication and maintain its low cost. This transceiver is based on TI’s lbc4 linear Bi CMOS process and operates with automotive battery voltage, so no external power supply is required. The fault protection function enables the equipment to withstand the voltage of – 40V ~ + 40V on the LIN bus, and the on-chip electrostatic discharge (ESD) protection function can withstand the peak voltage of up to 17kv (International Electrotechnical Commission) and 21kv (manikin). On this basis, more components required to connect the sensor or transmission to the automotive power grid and Lin network can be integrated. Typical on-chip functions include: Automotive voltage regulator meeting system requirements, analog filtering function of front-end input in sensor output, analog-to-digital converter (ADC), digital filtering and control, and Lin compatible protocol controller. Figure 1 illustrates a fully integrated sensor interface based on lbc4. The high integration and circuit protection function of this device makes it suitable for the harsh automotive environment with very limited space and cost.

Lin communication bus standard and mixed signal semiconductor technology improve vehicle maintenance performance and reliability

Tpic10271 transmission interface is a device specially designed for automotive applications based on lbc-4d. It integrates a 3.3V voltage regulator / monitor with battery power, a high voltage interface to the user switch, a high side FET (field effect transistor) driver for position sensors or other types of sensors, two low side FET drivers for motor control relays, a feedback operational amplifier, a protection circuit, and a Lin compatible phy (Figure 2). The output is directly connected to the microcontroller used to control the algorithm, such as the anti crush monitoring function of the window regulator. Like other devices in tpic1021 and Ti mixed signal series products, tpic10271 enters the power-saving sleep mode during non operation, and has low electromagnetic interference (EME) and high anti electromagnetic interference (EMI).

For other applications, the same mixed signal technology can integrate not only the functional blocks of the above two devices, but also other functions, including low voltage drop and switching voltage regulators for single rail and multi rail, high / low side drivers with different configurations, various operation amplifiers, digital logic devices, Lin interfaces and other communication interfaces. Available transmission interfaces include: H-bridge, intelligent driver suitable for DC brush / three-phase DC brush motor, and relay driver. These drivers are used for power seats and mirrors, door locks, windshield wipers and defrosters, glass and antenna lifters, HVAC, and various other electronic systems to provide user comfort and safety.

System advantages

Changing the sensor / actuator signal and communication interface to a Lin compatible mixed signal IC can produce a variety of system level advantages. The first is to improve the system robustness and diagnosis function. Reducing the number of lines can reduce costs and potential fault sources. Because Lin can realize two-way communication, the master device can obtain diagnostic information from the sub device, and the slave device can provide fault information in case of system problems. In addition, Lin eliminates the need for proprietary interfaces and can develop components and software by adopting a general communication scheme based on open and reliable standards.

With Lin, sensors or drives that require only three wires (battery, ground and Lin) can be built, reducing wiring and harness requirements. The device housing is smaller for better sensor / drive arrangement without excessive consideration of wiring. Lin and advanced mixed signal technology can reduce the system cost in many aspects: the number of components is reduced; Inventory reduction; More compact and simpler printed circuit board and sensor / drive housing; Using on-chip oscillator instead of crystal oscillator or resonator system as clock source; Higher reliability. Some of the above factors can also reduce weight and space consumption – a constant pursuit in automobile design.

This progress is only the first step in the development of intelligence and function of automotive sensors and transmission devices. The next generation hybrid signal vehicle IC will integrate smaller microcontrollers, which can realize programmable functions and higher flexibility, so as to meet the future needs of vehicles. With the increasing intelligence of automotive sensors and transmission devices, automotive designers can freely imagine the intelligent application of automotive systems.

Responsible editor: GT

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