An interesting case study was presented for the automotive market for the advantages of supporting the deployment of standard Ethernet and active Ethernet (PoE), mainly due to higher profits than most deployments using this method. The automotive industry has changed dramatically, and consumer and government demand for safer cars has greatly boosted the use of advanced driver assistance systems (ADAS). ADAS features are increasingly becoming a standard feature of automobiles, such as rear-view parking sensors and cameras that have become quite popular. Looking ahead, these systems will be more complex, exemplified by increasingly sophisticated sensor-based anti-collision systems designed to provide lane departures, road signs, traffic lights, and pedestrian identification. This article refers to the address: http:// Standard Ethernet provides high-bandwidth data transmission over low-cost, unshielded twisted-pair lines, and this solution has proven to be very attractive for ADAS applications. Looking back at technology development from a historical perspective, it has been found that standards-based solutions are well understood, with multiple vendors serving multiple markets, resulting in economies of scale and ultimately providing the lowest cost of ownership. However, there are other overall advantages to adopting standard Ethernet based on a number of complementary IEEE standards, which is often overlooked. One example is the use of Active Ethernet (PoE). So how does it work? From the car manufacturer's point of view, adding multiple camera sensors around the car increases the wiring content, no surprises, which is what they don't want to see. In addition, remotely located automotive sensors also need to transmit power along the data wiring. This usually results in an additional pair of wires for each sensor to remotely power each device. However, IEEE 802.3af (standard) and IEEE 802.3at (power-enhanced) specify the way in which power is distributed over the same cable based on data—using this type of technology means that remote sensor devices using standard Ethernet interfaces effectively eliminate The need for additional cables. In this example, not only is the number of wires reduced, but the advantages of using this standard technology to demonstrate this stable technology also benefit automotive applications – without adding additional system costs. The basic principle of IEEE802.3af/at PoE operation is shown in Figure 1. This explains how it can be implemented without adding additional system costs. Figure 1. IEEE802.3af/at active Ethernet; principle of phantom powering As shown, the PoE architecture consists of two major elements. The Power Supply Equipment (PSE) supplies power and the Power Receiving Equipment (PD) receives power. The dedicated PSE controller must detect and classify the PD and then power it in three phases: Discovery: PSE confirms whether it is connected to a valid and compatible device; Category: PSE checks the power requirements of the PD; Run: If No. 1 and Condition 2 does work and the PSE provides sufficient power, and the PSE will enable the VPSE voltage (between 44V and 57V). As a "phantom power" technology, the PoE voltage VPSE is applied to the center tap of a standard 100BASE-TX Ethernet transformer. The current flows down the two wires to the center of the Ethernet transformer at the PD end. Each winding carries the opposite current of half of the electrodes, so the total DC current through the transformer should actually be zero. This "phantom power" method has the important advantage of suppressing the common mode noise of the PD transformer, but this only applies to the 100BASE-TX Ethernet interface. As the common mode noise is dissipated into the differential Ethernet signal and cleared, the noise emitted by the PSE or the noise extracted along the twisted pair cable will couple. If the RX and TX wiring pairs are accidentally swapped, the PD side needs to use a bridge rectifier to enable rectification and function in a polarity insensitive manner. The center taps of the other transformers provide the ground loop path of the PSE, which creates a second important advantage, namely galvanic isolation of the PD and PSE ground. When the ground potentials at both ends are different, the role of galvanic isolation is very important to prevent the formation of a radiated ground loop - a situation that is likely to be significant for a car. This advantage is also unique to installing 100BASE-TX Ethernet. How phantom power can optimize for automotive applications There are considerable opportunities for optimization when using such IEEE PoE methods for automotive applications (Figure 2). Eliminating traditional PSE controllers is the main difference. This may be due to the known and fixed PD side of the automotive application, so there is no need to go through the discovery and classification stages. Let us consider the interface between the camera module and its head unit as an example. In this case, the relatively expensive PSE controller can be replaced with a low-cost DC-DC regulator to provide shutdown protection in the event of a current overload fault. With a lower PoE voltage VPSE, such as 12 V, which is more suitable for automotive applications, a lower voltage (and lower cost) DC-DC regulator can also be used on the PD side. It should be noted that each port can achieve a power rating of approximately 6W from 12V PoE operation, and a higher PoE voltage (or enhanced current rating magnetism) can be used if additional power is required. Another advantage is that since the car wiring will also be fixed, the PD terminal no longer requires a common bridge rectifier. Figure 2. Optimization opportunity to use "phantom powered" 100Base-TX PoE cars Table 1. Automotive PoE cost and performance advantages Despite being optimized and reducing the final cost, the standard Ethernet PoE for automotive applications has other advantages due to the “phantom power†approach. In particular, PD-side common mode noise suppression and PD / PSE ground isolation are shown in Table 1. It is clear that in automotive applications, IEEEPoE has all the advantages and no additional cost. There are no additional wiring and existing standard Ethernet magnetic components and existing standard power management can be used. 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