 The target of this presentation is to show the advantage of an integrated protection for power over Ethernet. PoE. Ethernet is everywhere. Most of you know and probably use it. It is one of the most popular links for data transfer. The big advantage? It is plug and play. The main disadvantage? It requires a power adapter. PoE embeds a 48 volt power supply up to 15 watt for standard PoE and 30 watt for the PoE plus. For backwards compatibility, PoE and PoE plus are fully compatible in terms of Ethernet data. It uses the same RJ45 plug and the same cable, so it is transparent to the user. Most of the small applications such as cameras, small Wi-Fi routers, IP phones can be supplied by a PoE switch. For a basic PC printer user, the interest may probably be low because an AC adapter will be required in any case. Removing the requirement for an AC adapter makes applications more cost effective. They are less expensive and cheaper to install as there is no need to get a power cable nearby. PoE is made of three parts. The terminal such as a camera or an IP phone also called the power device, PD. This part transmits and receives data as well as receiving power. The cable to transmit data and power. This is the same cable as for Ethernet. The last part is the power sourcing equipment, PSE. This part transmits and receives as well as delivering power. How does it work? For data, there is no difference with Ethernet. Each differential pair transmits data. To deliver power on the PSE side, the midpoint of one transformer is connected to ground and midpoint of a second one to minus 48 volts. On the PD side, the same connection is made and a DC to DC converter provides the correct DC voltages for the internal circuit boards. To better understand, here is the schematic for two power over Ethernet links. To make it more readable, we have represented a 100 megabit per second line, where only two pairs are used for data, but the concept is the same for one or 10 gigabit per second links. On some applications, the minus 48 volts is directly provided by the PSE controller. In this schematic, we use power MOSFETs. On the power device side, a basic diode bridge and a small DC to DC converter delivers the required voltage, for instance, for a camera. In theory, this works well, but in practice, cables are often subject to electrical disturbances and required to comply with surge standards such as IEC 61000-4-5. In that case, protection is required for both data and power supply lines. In most applications, protection is achieved by a TVS, such as a SMBJ58A or SM6068A on each power supply. All these protection devices are general purpose protection, specified with 10 by 1000 microsecond surge. But the question is, is it the right way to specify this protection? To answer this, let's take a look at the standards generally used. The IEC 61000-4-5. IEC 61000-4-5 is defined to simulate lightning and industrial disturbances. It specifies the environment, which is depending on where the equipment is located. Let's focus on the most used classes, class 1 and class 2. Depending on the environment, various surge levels must be applied. Ethernet equipment must generally comply with class 1, 500 volt surge, or class 2, 1 kilovolt surge. IEC 61000-4-5 specifies other voltages, but they are generally not used for PoE. IEC 61000-4-5 defines three different surge impedances for the surge generator. For power supply lines, the surge generator is used alone with its 2 ohm internal resistance, or with an additional 10 ohm resistor. For data lines, and this is a case for Ethernet and Ethernet PoE, an additional 40 ohm resistor is used. This leads to a current of 12 or 24 amps. The IEC surge generator is a combination wave generator, which means the voltage waveform in an open mode, 1.2 by 50 microseconds, is different from the current waveform in short circuit, 8 by 20 microseconds. Required surge specification is 8 by 20 microseconds and not 10 by 1000 microseconds. General purpose protection is, therefore, not well specified for this particular application. Many of the applications embed several Ethernet ports, and quite often the number of ports is a multiple of four. All equipments embed one SMA or SMB device per connector. As the number of connectors is a multiple of four, ST microelectronics has implemented four protection devices and four capacitances in an SO8 package. As we are talking about DC lines, there is no specific recommendation for layout, so there is no issue to use an integrated solution. ST's PEP01-5841 or PEP01 has been designed and specified to meet IEC 61000-4-5 with 1 kilovolt, 24 amps, and a maximum clamping voltage, VCL, equal to 100 volts, which generally corresponds to the technology of the power source equipment controller or to those of the power MOSFETs. As routers and switches embed more and more lines per board, space saving is a key point. Comparing four SMB packages, plus four capacitors, occupying 82 square millimeters total, without taking into account the space between the packages, and the 30 square millimeters of the SO8 package, ST's PEP01 provides a space saving of 74 percent. The SMB-J58A is a general purpose protection manufactured by several suppliers, with a maximum leakage current of one microampere at 25 Celsius degrees, at 58 volt, and with a surge specification defined in 10 by 1000 microseconds instead of 8 by 20 microseconds. The PEP01 is defined according to telecom operating temperature range, which is up to plus 85 Celsius degrees, with a maximum leakage current of one microampere at 85 Celsius degrees, and only 0.2 microampere at 25 Celsius degrees. This is five times lower than all our competitors. The PEP01 provides two big advantages regarding surge capability. First, it is rated with 24 amperes, 8 by 20 microsecond surge, to comply with IEC 61000-4-5 1 kilovolt. Second, the maximum clamping voltage is 100 volts to be compatible with PoE, controller technology, or 100 volt power MOSFETs. We also specify the dynamic resistance, RD, to calculate the maximum clamping voltage, VCL, whatever the surge current is, with a formula given in the data sheet. Last but not least, alpha T can be used to calculate the maximum clamping voltage, VCL max, depending on the temperature, with a formula given in the data sheet. In this case, the PSE controller embeds the power MOSFETs to deliver power. The PEP01 is used to protect the PSE controller. On this schematic, the PSE controller does not embed power MOSFETs. It is required to add them externally. The PEP01 is used to protect the four MOSFETs. The PEP01 is used to protect according to IEC 61000-4-5 up to 1 kilovolt. In the case of a harsh environment, it can be necessary to protect against 2 kilovolts. The use of discrete devices, such as SMBJ58A series, imposes to pair up two devices in parallel or to use one SMCJ58A per PoE power supply. One of the advantages of the integrated protection is the possibility to increase the surge capability without pairing up the protection because the four cells have the same characteristics. Then, paralleling two cells is possible with a 50% sharing of the current in each TVS. In this case, layout is sensitive to keep the same resistance and inductance for each cell to have good current sharing. This achieves a protection according to IEC 61000-4-5 at 2 kilovolts under 42 ohms. To summarize, the integration of four protection devices and capacitance allows to save PCB area or to have more lines per board, making applications more compact and cost effective. The equipment will be fully protected according to IEC 61000-4-5 up to 2 kilovolts. The design of the PEP01 is made to be compatible with PoE controller and power MOSFET technologies, which are generally 100 volt rated. The PEP01 is rated with a low leakage current at 85 Celsius degrees to limit power consumption. This protection has been developed according to IEEE 802-3AF and IEEE 802-3AT. This device is a cost effective solution to protect PoE equipment because it contributes to reduce the PCB area. The PEP01 is correctly specified according to IEC 61000-4-5 to avoid field return and is more cost effective than using four SMBJ58A devices. For more information, visit our website at www.st.com.pep01. Thank you for your attention.