1 dc2476aafb DEMO MANUAL DC2476A-A DESCRIPTION LT4295, LT4321 High Efficiency IEEE 802.3bt (PoE++, Type 4, 62W/71W) PD with Flyback DC/DC Converter and Auxiliary Supply Input Demonstration Circuit 2476A is an IEEE 802.3bt (Draft 2.2) compliant power over ethernet (PoE) powered device (PD). It features the LT ® 4295 PD interface and switch- ing regulator controller and the LT4321 PoE ideal diode bridge controller. The LT4295 provides IEEE 802.3af (PoE, Type 1), IEEE 802.3at (PoE + , Type 2), and IEEE 802.3bt (PoE ++ , Type 3 and 4) compliant interfacing and power supply control. It utilizes an external, low R DS(on) (30mΩ typical) N-channel FET for the hot swap function to improve efficiency. The LT4295 controls a DC/DC converter that utilizes a highly efficient flyback topology with synchronous rectification. The LT4321 controls eight low R DS(on) (30mΩ typical) N-channel FETs to further improve end-to-end power L, LT, LTC, LTM, Linear Technology, LTPoE++ and the Linear logo are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners. PERFORMANCE SUMMARY BOARD PHOTO delivery efficiency and ease thermal design. This solution replaces the eight diodes typically found in a passive PoE rectifier bridge. The DC2476A-A accepts up to 71W of delivered power from a power sourcing equipment (PSE) via the RJ45 connector (J1) or a local 48V DC power supply using the auxiliary supply input. When both supplies are connected, the auxiliary supply input has priority over the PoE input. The DC2476A-A supplies a 24V output at up to 2.7A. Design files for this circuit board are available at http://www.linear.com/demo/DC2476A-A PARAMETER CONDITIONS VALUE Port Voltage (V PORT ) At RJ45 37V to 57V Auxiliary Voltage From AUX+ to AUX– Terminals 37V to 57V Output Voltage (V OUT ) 24V (Typical) Output Current (I OUT ) 2.7A (Max) Output Voltage Ripple V PORT = 41.2V, I OUT = 2.7A 200mV P-P (Typical) Load Regulation 0.5% (Typical) Efficiency V PORT = 50V, I OUT = 2.7A, End-to-End 91.5% (Typical) Switching Frequency 250kHz (Typical) Top Side Bottom Side
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1dc2476aafb
DEMO MANUAL DC2476A-A
Description
LT4295, LT4321 High Efficiency IEEE 802.3bt (PoE++, Type 4, 62W/71W) PD
with Flyback DC/DC Converter and Auxiliary Supply Input
Demonstration Circuit 2476A is an IEEE 802.3bt (Draft 2.2) compliant power over ethernet (PoE) powered device (PD). It features the LT®4295 PD interface and switch-ing regulator controller and the LT4321 PoE ideal diode bridge controller.
The LT4295 provides IEEE 802.3af (PoE, Type 1), IEEE 802.3at (PoE+, Type 2), and IEEE 802.3bt (PoE++, Type 3 and 4) compliant interfacing and power supply control. It utilizes an external, low RDS(on) (30mΩ typical) N-channel FET for the hot swap function to improve efficiency. The LT4295 controls a DC/DC converter that utilizes a highly efficient flyback topology with synchronous rectification.
The LT4321 controls eight low RDS(on) (30mΩ typical) N-channel FETs to further improve end-to-end power
L, LT, LTC, LTM, Linear Technology, LTPoE++ and the Linear logo are registered trademarks of Analog Devices, Inc. All other trademarks are the property of their respective owners.
performance summary
BoarD photo
delivery efficiency and ease thermal design. This solution replaces the eight diodes typically found in a passive PoE rectifier bridge.
The DC2476A-A accepts up to 71W of delivered power from a power sourcing equipment (PSE) via the RJ45 connector (J1) or a local 48V DC power supply using the auxiliary supply input. When both supplies are connected, the auxiliary supply input has priority over the PoE input. The DC2476A-A supplies a 24V output at up to 2.7A.
Design files for this circuit board are available at http://www.linear.com/demo/DC2476A-A
PARAMETER CONDITIONS VALUE
Port Voltage (VPORT) At RJ45 37V to 57V
Auxiliary Voltage From AUX+ to AUX– Terminals 37V to 57V
Figure 6. Load Transient Response (Conditions: VPORT = 41.2V, Load Step: 1.35A to 2.7A to 1.35A)
6dc2476aafb
DEMO MANUAL DC2476A-A
typical performance characteristics
Figure 7. Gain and Phase Margin of the Flyback DC/DC Converter (Conditions: VPORT = 57V, VOUT = 24V, IOUT = 2.7A)
CROSSOVER FREQUENCY GAIN MARGIN PHASE MARGIN
3.8kHz 18dB 64°
7dc2476aafb
DEMO MANUAL DC2476A-A
Quick start proceDurePower over Ethernet (PoE) Input
1. Disconnect auxiliary supply if it is connected to AUX+ and AUX– inputs of the DC2476A-A.
2. Place and connect test equipment (voltmeter, ammeter, oscilloscope and electronic load) as shown in Figure 8.
3. Turn down the electronic load to a minimum value and turn off the electronic load.
4. Connect the output of the IEEE 802.3bt compliant PSE to the RJ45 connector (J1) of the DC2476A using a CAT5e or CAT6 Ethernet cable. (See Note.)
5. After the LED (D4) on the DC2476A is lit, check the output voltage using a voltmeter. Output voltage should be within 24.0V ±0.3V.
6. Turn on the electronic load and increase its load cur-rent up to 2.7A. Observe the output voltage regulation, efficiency, and other parameters.
7. Verify T2P response with an oscilloscope as shown in Figure 8. The T2P response to the type of PSE connected to the DC2476A-A is provided in Table 1.
Note: An 802.3bt PSE has not yet been released. In the interim, an LTPoE++® compliant PSE (DC1814A-D) may be used to provide power to the DC2476A-A. The LTPoE++ classification will not be 802.3bt compliant, but the PSE will provide a compatible detection and power output. Specifically, the T2P output of the DC2476A-A is different from the behavior stated in Table 1 and will indicate connection to a Type 2 PSE. Otherwise PD behavior will be unaffected.
Figure 8. Setup Diagram for PoE Input
Table 1. T2P ResponsePSE T2P Response Negotiated PD Input Power
IEEE
Logic High 13W
Logic Low 25.5W
50% Logic High/50% Logic Low, Toggle at 976Hz ±7% 51W
75% Logic High/25% Logic Low, Toggle at 976Hz ±7% 71W
LTPoE++, 90W Logic Low 71W
VOLTMETER
+
– AMMETER
+
–
ELECTRONICLOAD
+
–
OSCILLOSCOPE+
–
DC2476AA F09
IEEE 802.3btPSE
CAT5eOR CAT6CABLE
+
–
DC POWERSUPPLY
+
–
8dc2476aafb
DEMO MANUAL DC2476A-A
Quick start proceDureAuxiliary Supply Input
1. Place and connect test equipment (voltmeter, ammeter, oscilloscope and electronic load) as shown in Figure 9.
2. Turn down the electronic load to a minimum value and turn off the electronic load.
3. Connect the output of the auxiliary supply to the DC2476A as shown in Figure 9. Turn on the auxiliary supply and set its current limit to 2A. Then increase its output voltage to 48V.
4. Once the LED (D4) on the DC2476A is lit, check the output voltage using a voltmeter. Output voltage should be within 24.0V ±0.3V.
5. Turn on the electronic load and increase its load cur-rent up to 2.7A. Observe the output voltage regulation, efficiency, and other parameters.
6. Verify T2P response with an oscilloscope as shown in Figure 9. The T2P response during auxiliary power operation is: 75% Logic High/25% Logic Low, Toggle at 976Hz ±7%.
Figure 9. Setup Diagram for Auxiliary Supply Input
VOLTMETER
+
– AMMETER
+
–
ELECTRONICLOAD
+
–
OSCILLOSCOPE+
–
AUXILIARYSUPPLY
+ –
DC2476AA F09
9dc2476aafb
DEMO MANUAL DC2476A-A
parts listITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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14dc2476aafb
DEMO MANUAL DC2476A-A
LINEAR TECHNOLOGY CORPORATION 2016
LT 0817 REV B • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.