QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 859 MULTIPLE OUTPUT PD LTC4267 DESCRIPTION Demonstration circuit 859 is a Multiple Output PD fea- turing the LTC4267. The board provides a complete The LTC4267 combines the above features with a cur- IEEE 802.3af power device (PD) interface and isolated rent mode switching controller designed for driving a 6V power supply solution for use in Power over Ethernet rated N-channel MOSFET. It features programmable (PoE) applications. It generates 1.8V 2.5A, 2.5V slope compensation, soft-start, and constant frequency 1.5A and 3.3V 0.5A. operation, minimizing electrical noise even with light loads. The LTC4267 integrates the 25kW signature resistor, classification current source, thermal overload protec- Design files for this circuit board are available. Call tion, signature disable and power good signal along with the LTC factory. an undervoltage lockout optimized for use with the IEEE , LTC and LT are registered trademarks of Linear Technology Corporation. required diode bridge. The precision dual level input current limit allows the LTC4267 to charge load capaci- tors and interface with legacy PoE systems. Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Turn-on Voltage Input from PSE -36V maximum Maximum Turn-off Voltage Input from PSE, PD switch turns off -32V Power Converter Input operating range V =3.3V, I = 0 to 2.6A -37V to -57V OUT OUT Maximum Input Current Input from PSE, PD high level current limit 375 mA, typical V =1.8V 2.5A OUT1 Maximum Output Current V =2.5V 1.5A OUT2 V =3.3V 0.5A OUT3 1.79V, typical Output Voltage V =48VDC from PSE 2.5V, typical IN 3.3V, typical V = 1.8V, V = -37 to -57VDC, zero to full load + 5% OUT1 IN Output Regulation V = 2.5V, V = -37 to -57VDC, zero to full load + 2% OUT2 IN V = 3.3V, V = -37 to -57VDC, zero to full load + 5% OUT3 IN 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 859 MULTIPLE OUTPUT PD QUICK START PROCEDURE Demonstration circuit 859 is easy to set up to evaluate 4. Turn on the PSE or alternate input power supply and the performance of the LTC4267. For proper equipment increase the voltage until the power converter turns setup, refer to figure 1 and follow the procedure below: on. Be careful not to exceed 57VDC. NOTE: Make sure that the input voltage does not exceed 57VDC. If a higher voltage is required, power components 1. With the power source to the PSE turned off, con- with higher voltage ratings should be used. nect the input power supply to the board through the 5. Verify proper classification and signature detection. J1 filtered Ethernet connector. 6. Check the output voltages. They should be as listed 2. In addition to a PSE, the DC859 board can be pow- in table 1. If there is no output, temporarily discon- ered by an alternate input power supply through the nect the load to make sure that the load is not set V+ (TP5) and VPORTN (TP14) terminals. Do not too high. connect more than one power source. 7. Once the proper output voltage is established, adjust 3. Set the SIGNATURE jumper (JP1) to the ENABLE the load current within the appropriate range and position. observe the output regulation, ripple voltage, effi- ciency and other parameters. OPERATION Demonstration circuit 859 interfaces with a customers displays the proper 25kW signature resistor. Signa- Power-Over-Ethernet test setup per Figure 1. The front ture detection may be disabled, if so desired, by set- end of the demo circuit implements the required ting the SIGNATURE jumper (JP1) to the DISABLE po- Ethernet input interface transformer coupling and sition. If signature classification is disabled, all inter- common-mode termination through the integrated face functions of the LTC4267 are disabled. Signature connector J1. The demonstration circuit is set up to detection, classification and the internal power allow data to pass in and back out of the demo circuit MOSFET switch are all disabled. while the DC859 performs IEEE 802.3af interface func- tions. The Power Sourcing Equipment (PSE) is con- Classification is programmed by the selection of a sin- nected to J1 and the PHY is optionally connected to gle external resistor, RClass, connected to the RCLASS J2. pin on the LTC4267. After detection and classification, the PD is powered The PD is required to have 0.1uF of capacitance during up when the input voltage exceeds the LTC4267 turn- detection this is provided by C2. It is also required to on under-voltage lock out (UVLO) through a dual-level have at least 5uF of capacitance after the in-rush cir- current-limited power switch. While the voltage be- cuit, provided by capacitors C1 and C9. tween POUT and VPORTN is above the Power Good This demo circuit allows detection and power classifi- trip point, the amperage through the power switch is cation of the PD per the IEEE 802.3af specification. held below the low-level current limit. When the volt- During the detection process of a PD, the LTC4267 age between POUT and VPORTN falls below the Power 2