More intelligent cars require a wide variety of robust yet inexpensive sensors, many of which have proven highly applicable to other embedded systems. Furthermore, digital programming techniques are simplifying the development process for adapting these automotive sensors to new applications. Currently, cars, trucks, and buses are not only mechanical devices but also almost entirely electronic. As more cars add advanced features such as stability control and electronic throttle control, their electronic content continues to increase. Since electronic systems operate solely on electrical signals, cars require sensors to convert various optical, chemical, and mechanical stimuli into electrical signals. While sensors have historically been very expensive, automotive sensors cannot be too pricey, as cost remains a critical factor in automotive manufacturing (even for high-end luxury cars). However, despite these strict cost constraints, automotive sensor designers cannot simply cut corners. These sensors must operate reliably for many years under harsh conditions of temperature, humidity, shock, vibration, and electromagnetic interference—conditions that significantly shorten the lifespan of conventional sensors. This challenging situation is actually good news for designers of embedded systems based on non-automotive sensors. These designers often find that they can adapt sensors originally developed for automobiles to other applications. This is because automotive sensors, while inexpensive, are extremely reliable. Furthermore, current programmable technology facilitates the modification of the ever-growing number of automotive sensors to meet the requirements of new uses. Many automotive sensors are now manufactured using IC processes, some of which produce chips with both analog functionality and non-volatile memory. This approach allows for the calibration and programming of each device to compensate for manufacturing defects. Therefore, programmability allows device manufacturers to loosen tolerances, thereby reducing costs while increasing device yield. However, IC designers must carefully consider whether increasing programmability truly reduces the cost of sensor chips. This trade-off can be extremely tricky. If not carefully considered, adding non-volatile memory to a primarily analog chip can increase, rather than decrease, costs. Combining non-volatile RAM with analog functionality requires more complex wafer fabrication processes; memory increases chip area, thus reducing yield, while programming increases testing time. While there are compelling reasons for the increasing dominance of IC technology in automotive sensing, not all automotive sensors are IC-based. Far from it. However, currently, no other manufacturing technology is as well-suited for producing these sensors. The batch processing technology for IC manufacturing allows for the production of large quantities of devices with precisely controlled functionalities, resulting in extremely low device costs. In fact, the packaging cost of many automotive sensor ICs is already higher than the cost of the chip itself. Even so, the cost of packaged devices is generally lower than devices produced by other methods. It can be said that in many cases, even if automakers were willing to pay a considerable price (and in fact, they are not), suitable devices simply cannot be produced by other methods. Packaging accounts for a significant portion of the cost . It is no surprise that packaging costs constitute a large proportion of the cost of automotive sensors. The packaging must protect the already fragile chip from extreme environments. Furthermore, some IC sensors place extremely demanding requirements on the packaging. For example, some position sensors require precise monitoring of the IC chip's position relative to external features of the package. Meeting these requirements necessitates specialized assembly processes and fixtures. Even without such specific requirements, automotive sensor packaging must protect the chip from operating conditions that most commercial devices never encounter. Not only the chip, but the package itself must be able to operate normally within a temperature range of -40 to +125°C (for ICs mounted on engine components, the operating temperature range is -40 to +150°C). Furthermore, the package must protect the chip from high humidity and, in some cases, from salt spray. It must also protect the chip from extreme shocks and vibrations, while the chip itself must withstand strong electrostatic and RF electromagnetic interference. These requirements are typically the same as those for ICs used in military and aerospace equipment, with only slight relaxations per unit volume in certain cases. Automotive companies don't pay military prices; in some cases, they even demand prices lower than those for ordinary goods. You might think that using the same sensors extensively in automotive systems would make custom packaging appealing to automotive customers. However, automotive sensor buyers prefer standardized packaged ICs whenever possible, at least from a size perspective. The basic structure of standard packages (such as test sockets) already exists, making it easier to find multiple manufacturers of standard packaged ICs than multiple manufacturers of specialty packaged ICs. IC sensor manufacturers estimate that at least half of the automotive sensors they produce are packaged in industry-standard form factors. Although the dimensions are standardized, almost all of these packages are versions adapted for the automotive industry by IC or packaging manufacturers. ISO (International Organization for Standardization) has established standards for various aspects of the performance of automotive ICs and IC packages. One such standard, ISO/TR7637/1, includes specifications for the device's ESD (electrostatic discharge) resistance. Sometimes, modifying commercial-grade devices for automotive applications requires more special attention to the packaging. Various modifications may necessitate significant changes to the wafer fabrication process. This is the case, for example, with light sensors mounted under the hood. Generally, photodiode detectors can only operate at temperatures up to 85°C; above this temperature (and in some cases, above 100°C), the leakage current of reverse-biased photodiodes becomes excessive. However, changing the doping of the device allows it to operate at an ambient temperature of 125°C. The Spiral Supply Chain Most of the purchasers of sensors are not the automakers themselves, but rather their suppliers or suppliers of components to the automakers. For example, Company A might sell power window regulators (special motors) to Company B, while Company B sells the complete door assembly to Company C, the car manufacturer. In this scenario, Company B is the most likely company to need a second supplier; however, Company B might mistakenly believe it has multiple suppliers. Suppose the power window regulator is a newer "one-touch up" device primarily manufactured with an electric motor, containing a lever (or obstruction) sensor. To prevent injury from someone blocking the window's upward movement with their hand or neck, older regulators required the driver or passenger to hold down the button throughout the upward movement. The "one-touch up" regulator only requires a single press; if a sensor on a chip determines that the motor's torque is too high, the control IC within the motor will reverse the window's movement. Even if Company B has a second supplier, D, that can supply the regulator, both Company A and D might obtain the lever-detecting motor control IC from Company E. Therefore, if a problem occurs at Company E, the supply of such regulators to Companies A and D will cease. Some non-automotive embedded systems use components developed for automotive devices. One concern for developers of such non-automotive embedded systems is the availability of necessary future support. Many non-automotive companies want to purchase these components, but in smaller quantities, only a few thousand or even a few hundred, while automotive suppliers contract to purchase hundreds of thousands or millions of components. Semiconductor manufacturers have several responses to this question. First, they say they recognize the overall sales potential of non-automotive sensors as a potentially lucrative business. To provide device designers with the information they need, most IC companies that manufacture automotive sensors publish detailed datasheets containing all the information required by design engineers intending to use these components in non-automotive devices. IC companies are also working to improve the application support capabilities of their distributors. Furthermore, several IC companies say their factory application support staff are genuinely eager to assist customers with smaller purchase volumes. Some companies (such as Melexis) not only provide demonstration boards but also development kits for their sensor products. Melexis has established its own website allowing customers to purchase these devices online. Sensors containing non-volatile RAM are available for online purchase because programmability is a critical issue for sensor specification developers and device designers using these devices. IC companies recognize that they must provide the information and equipment that enables designers to program sensors in the lab. Furthermore, device manufacturers often need to program sensor ICs using different tools in production, and IC companies commit to providing or developing the necessary resources for this. Diversity Needs Modern automobiles use a wide variety of sensors. Figure 1 shows where several sensors are installed in modern luxury cars. Table 1 lists several measured parameter values ​​and the technologies commonly used to measure these parameters (sensor types). However, this matrix is ​​incomplete. For example, it does not include flow sensors, nor does it list sensors that detect specific chemical components and elements (such as O2) (Figure 2). Chemical sensors are key components in automotive emission control systems. Available components and technologies are described relatively comprehensively. However, it's important to remember that because this book was written by a major automotive sensor manufacturer, the examples cited are all from their own company's various product lines. One sensing technology currently considered almost synonymous with automotive equipment is accelerometers based on MEMS (Micro-Electro-Mechanical Systems) technology. Although the fabrication of MEMS devices is closely related to IC manufacturing, and some MEMS-based sensors are simply chips that combine sensing elements with IC signal conditioners, MEMS manufacturers prefer not to call their products ICs. However, some mass-produced, fingernail-sized (or smaller) inexpensive devices capable of detecting or generating motion are novel and unique enough to evoke a science fiction feel. Undoubtedly, the application of MEMS-based automotive sensors will continue to expand beyond today's capacitive accelerometers. Indeed, MEMS is likely to become the leading automotive sensor technology; for example, some MEMS manufacturers are reportedly actively developing MEMS-based gyroscopes. Far less appealing than MEMS sensors, but still extremely important, are magnetic devices. While rotational position and velocity sensors largely utilize the Hall effect, some newer sensors are based on the GMR (Giant Magnetoresistance) effect. GMR technology has garnered significant attention due to its importance in increasing the areal density of hard disk drives. However, the advantage of Hall effect devices lies in their ability to combine detection and signal conditioning functions onto a single IC chip. Figure 3 illustrates the application of a magnetoresistive angle sensor in an automobile. Setting up a bus in a car The methods by which automotive sensors provide data are the subject of many papers. Most sensors are essentially analog sensors that detect physical phenomena in an analog manner. For decades, the analog output produced by each sensor has been unique for the range of variables detected by that sensor technology. Converting these output signals into a usable form is the task of a separate signal conditioner, which typically appears as a circuit module. The output of a sensing element is often a low-level analog voltage or current, and often a nonlinear function of the detected variable. Modern (or non-existent) calculation functions require linearized high-level outputs, scaled to the measured variable, and often corrected for compensation and gain. Later, several sensors and signal conditioning circuits were often integrated together, and the output was set to a standard range value. In industrial applications, especially in process control, the nominal output range is 4–20 mA. The significant reduction in size and cost of A/D converters has enabled the production of small digital output signal conditioners that cost almost as little as analog circuits. The widespread adoption of digital communication has driven the design of signal conditioners that can communicate via standard digital protocols. The development of IC-based sensors has made it possible to integrate sensors, signal conditioners, and standardized digital interfaces onto a single low-cost IC. Even so, many modern cars still use modular signal conditioners, such as the one shown in Figure 3. While this outcome sounds impressive, it's not without its problems. A major issue is that mastering this technology is too easy, or that too many electronics engineers are too creative, or that they overestimate their creativity. It seems that every living electronics engineer has designed at least one new bus and associated communication protocol, and any two of these buses and protocols are incompatible. The Tower of Babel, built from too many incompatible bus and protocol "standards," results in a huge waste of time, effort, and money. The automotive industry cannot escape the impact of this bus competition. The most famous automotive bus is CAN (Controller Area Network). CAN initially had a following among European automakers. A newer bus is LIN (Local Interconnect), which is not intended to replace CAN but rather complements CAM. LIN is a low-cost bus used in applications where the safety of the car owner is not critical. On the LIN Association's website, you can learn that numerous automotive and electronics companies are using the LIN bus. Summary Sensors have already played a major role in automotive design. This role is becoming increasingly important with the proliferation of automotive functions such as stability control and electronic throttle control. For many types of sensors, only IC technology can produce devices that meet the automotive industry's requirements—that is, low-cost devices that can operate reliably for many years in extreme environments. ICs that combine sensing capabilities with non-volatile RAM allow device manufacturers to program the chips to compensate for manufacturing defects. However, designers must find ways to prevent the cost of such hybrid ICs from increasing. Programmability allows non-automotive embedded system designers to modify automotive sensors to suit their needs, achieving robustness and high reliability at low cost.