May 11, 2024

How automotive MOSFETs improve energy efficiency and quality reliability

When designing power systems for automotive electronics, engineers may encounter challenges that are common in any power application. Because the power device MOSFET must be able to withstand extremely harsh environmental conditions. Ambient operating temperatures exceeding 120 ° C will increase the junction temperature of the device, thereby causing reliability and other problems. In extreme environments (such as automotive electronics applications under the hood), a rapid rise in temperature can cause the MOSFET to turn on unexpectedly, causing the threshold voltage to approach zero volts.

In addition, the MOSFET must also be able to withstand the high voltage spikes caused by the switching off moment and the load dump fault. The large number of connectors in electrical wiring (located in appropriate locations to facilitate assembly and maintenance wiring) also greatly increases the possibility of interrupting the electrical connection to the device. The automotive industry is very concerned about quality and reliability, so MOSFETs must comply with the internationally recognized AEC Q101 standard.

Each of these aspects is very important. But there is another challenge, namely to provide higher energy efficiency. In the past few years, the proportion of electronically controlled car functions has increased dramatically. Therefore, the number of semiconductors in the car is also increasing. Some vehicles have more than 100 ICs. MOSFETs must be able to meet the ever-increasing energy requirements of powering more ICs. The development of the automotive subsystem itself also requires more energy. Electric steering systems and anti-lock braking systems, which are increasingly popular in light vehicles, are two good examples. In summary, all these trends have stimulated a strong demand for ICs that can carry more current.

To meet the demand for larger currents, semiconductor companies must develop power MOSFETs that can reduce the on-resistance (the resistance value when current flows). Compared with conventional MOSFETs, MOSFETs produced by trench semiconductor manufacturing processes help reduce the on-resistance by 20% to 40%.

But in recent years, advances in power MOSFET technology have reduced the on-resistance per silicon area to extremely low levels, so device manufacturers must now look for other ways to improve their products. This is especially important when using high-density trench technology to manufacture devices with low drain-to-source voltages. Protection is one of the strategies used by IC companies to provide performance advantages to their automotive customers.

More MOSFET options

To date, automotive designers who choose MOSFET devices have only two options: 1. Choose a "simple" PowerMOS with no protection strategy; 2. Choose a fully protected device that automatically shuts down when environmental conditions exceed specifications.

Unfortunately, fully protected devices with additional logic circuits and protection circuits also have the disadvantage that the cost of implementing protection is too high. Therefore, leading IC companies have been developing a new type of device to combine their respective advantages.

Philips Semiconductor's TrenchPLUS series products are a good example. TrenchPLUS fully integrates TrenchMOS technology and additional functions onto the chip. The TrenchMOS production process adopted in 1996 reduced the on-resistance RDS (on) of power MOSFETs by half. The advantages of TrenchMOS combined with other functions are that it can protect the system, save space, and does not require expensive smart power devices.

TrenchPLUS technology

TrenchPLUS devices integrate on-board temperature and current sensing features and additional resistors and diodes (including ESD protection). The TrenchPLUS solution helps system engineers create designs that can measure system activity during work to improve safety and optimize performance.

Figure 1 shows a typical component set of TrenchPLUS type devices.

Figure 1: Additional features that TrenchPLUS devices may have

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