Low-power devices in the 30 to 60V range are being integrated into monolithic ICs including serial interfaces and microcontrollers. Such a single application-specific IC can control a small motor or possibly an entire door node with motors and locks. For higher energy applications, where the cost or technology of a monolithic IC is not practical, integration can occur through the use of innovative packaging. Through the combination of high power MOSFETs with control integrated circuits contained within a single package, very high power intelligent systems are being built.

These intelligent devices offer improved monitoring of system performance and increase the reliability of the power system through integrated protection. Features such as over-current, over-voltage, and over-temperature protection are standard on these types of products. When the device senses the presence of one of these potentially catastrophic conditions, it can put the power MOSFET into a condition to self-protect the entire system. Additional diagnostic features can be integrated to monitor for open or shorted loads and help direct auto technicians to isolate and correct issues in the vehicle.

The last, and perhaps most important driving force behind all of these applications, and why many of these technologies are available, is product and system cost. In the automotive business, there is a constant push to reduce product and system cost. This is not only a push on the component cost but the entire cost of ownership of a vehicle.

For this article, reliability is also included as a cost driver. A low cost power device that leads to line or field failures is not a low cost device. When making decisions on components to be utilized in an automobile, the system designer must take cost and reliability as one major driving force.

The products discussed in this article are being designed specifically for automotive applications and systems and are characterized and qualified for automotive end use. The automotive market has established several product qualification standards for power and intelligent power devices. These are known as the AEC-Q100 and AEC-Q101 Automotive Electronics Council standards. Products developed and offered to the automotive market must be designed and characterized to meet these tough standards to assure the end system performance will meet the designer's, and more importantly, the vehicle owner's expectations for product value.

Conclusion
The breadth of power devices and design considerations in today's automobile has come a long way over the years from the 60 or 55V alternative that used to be one of the only design questions. With the proliferation of electronic systems for entertainment, instrumentation, power train control, safety, chassis and stability controls, and body and convenience features, the number of power devices in the typical automobile is in the hundreds and growing. Selecting the right device is now a complex challenge—but with many technical options available to meet the desired performance and cost objectives.

Jim Gillberg is director, Automotive Applications, and Gary Wagner is director, Body Electronics/Smart Switches, at Fairchild Semiconductor.