DEMO MANUAL DC2093A LT4275/LT4321 ++ LTPoE /IEEE 802.3at/ IEEE 802.3af Compliant Powered Device Interface Description Demonstration circuit 2093A features the LT 4275, a Many of the main features from the previous generation fourth generation powered device (PD) controller and the PD controller are included in the LT4275 PD controller. LT4321, an ideal diode bridge controller for Power over These include a power good indicator, a power sourcing Ethernet (PoE) applications. equipment (PSE) type indicator, and support for an auxil- iary power input. The major difference from the previous The DC2093A is available in DC2093A-A, DC2093A-B, and generation PD controller is that the LT4275 drives an DC2093A-C versions to meet the power level required by external N-channel Hot Swap FET at the PoE high side the PD application. The DC2093A-A features the LT4275A voltage rail. This allows the user to choose a low R DS(ON) PD controller. This controller supports the IEEE 802.3at N-channel MOSFET to maximize power efficiency, reduce + ++ (Type 2, PoE ), IEEE 802.3af (Type 1, PoE) and LTPoE heat dissipation, and ease thermal design. An LED status ++ specifications. LTPoE adds four power levels to the indicator is included to indicate that the Hot Swap FET is existing IEEE standard with 38.7W, 52.7W, 70W, and 90W fully turned on and the PSE is powering the PD. A suf- of delivered PD power at the RJ45 jack. The DC2093A-B ficient load to sink more than 10mA is also included to features the LT4275B PD controller and is compliant with assure the PSE maintains power to the PD and to meet the IEEE 802.3at and IEEE 802.3af specifications. The the DC maintain power signature current required by the DC2093A-C features the LT4275C PD controller and is IEEE 802.3at/IEEE 802.3af specification. compliant with the IEEE 802.3af specification. Simply connect the output of the DC2093A to the DC/DC All three assemblies of the DC2093A include a PoE ideal converter that is right for the application. Linear Technology diode bridge controller, LT4321, and eight N-channel FETs offers a variety of DC/DC converter solutions that can be to reduce heat, maximize power efficiency, and increase used with the DC2093A (eg DC894, DC1317, etc). delivered power compared to a conventional diode bridge rectifier. This controller is designed to be used in PoE ap- Design files for this circuit board are available at plications without corrupting the PDs signature resistance DEMO MANUAL DC2093A p Table 2. DC2093A Performance Summary PARAMETER CONDITION VALUE PD Input Voltage After Start-Up (V ) At the PD Ethernet Port 49.8V to 57V PORT ++ LTPoE 38.7W ++ LTPoE 52.7W 47.8V to 57V ++ LTPoE 70W 45.1V to 57V ++ LTPoE 90W 41.0V to 57V IEEE 802.3at (Type 2, 25.5W) 42.5V to 57V IEEE 802.3af (Type 1, 13W) 37V to 57V Efficiency DC2093A-A, V = 48V, I = 1.1A 99.2% (Typical) PORT LOAD DC2093A-B, V = 48V, I = 600mA 98.9% (Typical) PORT LOAD DC2093A-C, V = 48V, I = 350mA 98.5% (Typical) PORT LOAD ++ PoE Type Switching Frequency An LTPoE PSE is Powering a DC2093A-A 840Hz heory of t o ++ ++ IEEE 802.3at, and LTPoE power levels from 3.84W to When an LTPoE PSE is connected to the DC2093A demo ++ board RJ45 connector, J1, via a CAT5e or CAT6 Ethernet 90W. Refer to Table 3 for the power levels. If an LTPoE cable, the PSE initiates the detection process. During this power level is selected, an IEEE 802.3af or IEEE 802.3at compliant PSE will classify this PD as a Class 4 PD. The process, the PoE ideal diode bridge controller is inac- tive and the body diodes of the PoE ideal diode bridge DC2093A-B includes a preselected R resistor to support CLS IEEE 802.3at 2-event classification and this board does not MOSFETs form a silicon diode bridge. The PD solution presents a 25k resistive load to the PSE. After the PD contain jumper blocks. The DC2093A-C includes multiple has passed the detection process, the PSE uses an IEEE jumpers to support all IEEE 802.3af power levels. Table 3 ++ 802.3at/IEEE 802.3af or LTPoE classification method shows each shunt position and its associated class number to determine the power level the PSE can deliver to the and power level for the DC2093A-A and -C boards. Use Table3 as a selection guide to choose a suitable power PD. The PSE turns on the port and provides power to the PD if the classification is successful. Once the LT4275 level for the load. detects the PSE has turned on the port, it drives an external Table 3. DC2093A-A and DC2093A-C Shunt Positions for PoE N-channel MOSFET to ramp up the output voltage. After a Power Levels successful PD controller output turn on, the LT4275 drives PoE POWER LEVEL AT a power good indicator (PWRGD) and a PSE type indicator ASSEMBLY CLASS THE PD INPUT RCLASS JUMPERS (T2P) (DC2093A-A and DC2093A-B only). The PWRGD DC2093A-A & -C 0 13W JP1 JP2 indicator signals the load to start drawing current and the DC2093A-A & -C 1 3.84W JP3 JP4 LT4321 to turn on the appropriate PoE ideal diode bridge DC2093A-A & -C 2 6.49W JP5 JP6 MOSFETs with low R in the high current path. This DS(ON) DC2093A-A & -C 3 13W JP7 JP8 reduces heat dissipation and increases delivered power DC2093A-A 4 25.5W JP9 JP10 compared to the conventional diode bridge. The T2P in- DC2093A-A 4* 38.7W JP11 JP12 dicator signals the load the type of PSE powering the PD. DC2093A-A 4* 52.7W JP13 JP14 DC2093A-A 4* 70W JP15 JP16 Classification Signaling DC2093A-A 4* 90W JP17 JP18 The resistors at R and R determine the clas- CLS CLS++ ++ *An LTPoE PD will be classified as Class 4 by an IEEE 802.3at/af sification signature and sequence. The DC2093A-A in- compliant PSE. cludes user-selectable jumpers to support IEEE 802.3af, dc2093af 2 peration erformance summary