DEMO MANUAL DC2046A-F LT4276, LT4321 PoE PD with Synchronous Flyback and Ideal Diode Bridge DESCRIPTION Demonstration circuit 2046A-F is an Ethernet Alliance sized power supply that utilizes a highly efficient flyback certified PoE Powered Device (PD) with an isolated power topology with synchronous rectification. The LT4321 supply using synchronous flyback topology, featuring the provides further efficiency improvement by minimizing LT 4276 and ideal diode bridge controller (LT4321). the bridge losses. The LT4276 provides IEEE802.3af (PoE, Type 1), The DC2046A-F supplies a 5V output at up to 2.3A. It + ++ IEEE802.3at (PoE , Type 2), and LTPoE PD interfacing also demonstrates the use of an optional auxiliary power and power supply control. When the PD is fully powered, supply input of 48V. When present, the auxiliary supply the PD interface switches power over from the Power becomes the dominant supply over PoE to provide power. Sourcing Equipment (PSE) to the switcher through an Design files for this circuit board are available. external, low resistance, high power N-channel FET. The All registered trademarks and trademarks are the property of their respective owners. highly integrated LT4276 controls a high power, small- PERFORMANCE SUMMARY Specifications are at T = 25C A PARAMETER CONDITIONS VALUE Port Voltage (V ) At Ethernet Port 37V to 57V PORT Auxiliary Voltage From AUX+ to AUX Terminals 37V to 57V Output Voltage 5V (Typ) Output Current 2.3A (Max) Output Voltage Ripple V = 37V, I = 2.3A 30mV (Typ) PORT OUT P-P Output Regulation 0.2% (Typ) Efficiency V = 48V, I = 2.3A, End to End 90% (Typ) PORT OUT Switching Frequency 250kHz (Typ) BOARD PHOTOS Top Side Bottom Side Rev G 1DEMO MANUAL DC2046A-F TYPICAL PERFORMANCE CHARACTERISTICS Top Side Bottom Side Figure 1. Thermal Pictures V = 57V, 5V/2.3A PORT 92 5.20 5.15 90 88 5.10 86 5.05 84 5.0 82 4.95 4.90 80 V = 37V V = 37V PORT PORT 78 V = 48V 4.85 V = 48V PORT PORT V = 57V V = 57V PORT PORT 76 4.80 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 LOAD CURRENT (A) LOAD CURRENT (A) DC2046A-F F02 DC2046A-F F03 Figure 2. Efficiency (End to End) Figure 3. Output Voltage Regulation Rev G 2 EFFICIENCY (%) V (V) OUT