AD-PS3803-RD

PoE+ with Ideal Diode Bridge to Isolated Flyback DC/DC (12V, 2A)

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Figure 1 AD-PS3803-RD Board

The AD-PS3803-RD reference design is a power converter capable of harnessing any IEEE802.3at (PoE+, Type 2)-compliant downstream power over Ethernet (PoE) supply to provide a galvanically isolated DC power.

At the core of this solution is the LT8306 60V no-opto flyback controller, stepping down the 37V to 57V PoE input voltage to a 12V, 24W DC output.

The on-board LT4275 LTPoE++/PoE+/PoE power delivery (PD) controller handles interfacing and power delivery to any PoE supply.

The LT4321 ideal diode bridge controller is used for improved end-to-end power delivery efficiency and eased thermal design by utilizing low RDS(ON) N-Channel FETs, replacing the eight-diode configuration typically found in passive PoE rectifier bridge.

The AD-PS3803-RD also has auxiliary DC power support for a wide input range of 37V to 57V.

Features

  • Galvanically isolated 12 V flyback DC output with up to 24 W of output power capability

  • No transformer third winding or opto-isolator for output regulation

  • Supports IEEE802.3at (PoE+, Type 2) and IEEE802.3bt (PoE++, Type 3 and 4) interfacing and power supply control via a configurable jumper array

  • Supports a wide input DC auxiliary power of 37 V to 57 V

Applications

  • Industrial Automation

  • Surveillance Camera Systems

  • VoIP Phones

  • Payment Terminal Systems

  • Wireless Access Points

Block Diagram

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Figure 2 AD-PS3803-RD Simplified System Block Diagram

Specifications

Table 1 Board Performance Summary

Characteristic

Condition

Value

Port Voltage (VPORT)

At Ethernet Port

37 VDC to 57 VDC

Auxiliary Voltage (VAUX)

From AUX+ to AUX- terminals

37 VDC to 57 VDC

Output Voltage (VOUT)

VPORT = 54 V, IOUT = 100 mA to 2 A

12.0 V ±5%

Max Output Current (IOUTMAX)

VPORT = 54 V

2 ADC

Output Regulation

VPORT = 54 V, 0% to 100% of IOUT

± 0.30% of VOUT(Typ.)

Load Transient Response

Load step from 25% to 100%

±5%

Efficiency

VPORT = 54 V, IOUT = 2 A

85.4% (Typ.)

Components and Connections

Basic Input and Output Ports

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Figure 3 Basic Input Output Ports

Warning

Observe correct polarity for each port connection to prevent damaging the device.

Power Supply Ports

Power the board either through its RJ45 female connector (PoE input) or via its DC auxiliary terminals.

Both ports can handle input voltage of 37 V:sub:DC to 57 V:sub:DC.

  • P1 - RJ45 input port for PoE from PSE

  • AUX+ - Positive input terminal for auxiliary DC power supply

  • AUX- - Negative input terminal for auxiliary DC power supply

Output Ports

  • VOUT+ - Positive output terminal of the board

  • VOUT- - Negative output terminal of the board

  • TP14 - POE_OUT+ terminal. This is the positive terminal of the passthrough voltage from either the PoE input or the auxiliary input.

  • TP15 - POE_OUT- terminal. This is the positive terminal of the passthrough voltage from either the PoE input or the auxiliary input.

  • P2 - RJ45 output port for PHY

LED Indicators

  • DS1 - Indicator for successful PD and PSE handshaking. This should remain turned on during normal operation.

Test Points

Numerous test points such as turrets and test pads were added for easier probing of signals.

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Figure 4 Board Test Points

Ethernet Pairs

  • TP1 - DATA-1 wire pair test pad

  • TP2 - DATA-2 wire pair test pad

  • TP3 - SPARE-1 wire pair test pad

  • TP4 - SPARE-2 wire pair test pad

Accessory Test Points

  • TP5 - Turret for AUX+ terminal

  • TP6 - Turret for AUX- terminal

  • TP7 - Test pad for T2P~

  • TP8 - Test pad for PWRGD

  • VPORT+ - Test pad for the positive terminal of the rectified voltage after the ideal diode bridge

  • VPORT- - Test pad for the negative terminal of the rectified voltage after the ideal diode bridge

  • PWRGD - Power good indicator. This terminal is pulled high when negotiation with PSE is established and power is available. Logic level is equal to voltage at POE_OUT+ terminal with respect to POE_OUT-.

  • T2P~ - PSE type indicator. Pulled down when a IEEE802.3at (PoE+, Type 2) compliant PSE is connected. A square wave with 50% duty cycle can be read when a LTPoE+.+ compliant PSE is detected.

  • TP16 - Turret for VOUT+ terminal

  • TP17 - Turret for VOUT- terminal

Class Select Jumpers

The board’s operating power level can be configured by changing the position of the class select jumpers, allowing different PSEs to be compatible with the device.

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Figure 5 Class Select Jumper Array

Table 1: Jumper Position

Power Level

Jumper 1 Position

Jumper 2 Position

25.5 W

JP9

JP10

38.7 W

JP11

JP12

52.7 W

JP13

JP14

70.0 W

JP15

JP16

90.0 W

JP17

JP18

Circuit Evaluation

AD-PS3803-RD Quick Start Procedure

Power over Ethernet using a Power Sourcing Equipment (PSE)

Figures 6 and 7 show the setup for evaluating the AD-PS3803-RD using a PSE. A resistive load or an active load can be used at the output stage of the device.

Tip

Default class select shunt positions are at JP9 and JP10 on the AD-PS3803-RD board.

With this configuration, any PSE with sufficient power will turn on the board. Refer to Table 2 for the shunt positions in selecting a different power level.

  1. Check the power delivery capacity of the PSE, ensure that it can provide the required power and load.

    Important

    Avoid selecting a jumper configuration corresponding to a higher power level than the PSE can provide. Otherwise, the PSE will not turn on the board after its classification stage.

  2. Connect the output of the PSE to the RJ45 connector (P1) on the AD-PS3803-RD board using a CAT5e or CAT6 Ethernet cable.

  3. After connection has been established, verify that the LED (DS1) is on. This indicates successful handshaking between the PSE and AD-PS3803-RD.

  4. Check for the proper output voltages. The output at the VOUT+ and VOUT- ports should be regulated at 12 V (±5%).

  5. Once the proper output voltage is established, connect the load at the VOUT+ and VOUT- ports of the AD-PS3803-RD, observing proper polarity of the terminals.

  6. Adjust the load current within the operating range and observe the output voltage regulation, ripple voltage, and other parameters.

    Note

    The AD-PS3803-RD requires a very small minimum load to maintain good output voltage regulation. A Zener diode is placed on the output to clamp the voltage to 13V at no load.

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    Figure 6 AD-PS3803-RD Setup with a Power Sourcing Equipment (PSE)

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    Figure 7 AD-PS3803-RD Setup Using a PSE Board Module

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    Figure 8 Example Setup using a PSE Module (DC2541A)

Auxiliary Power Supply

Refer to Figure 9 for evaluating the AD-PS3803-RD using an auxiliary power supply. A resistive load or an active load can be used at the output stage of the device.

  1. Connect the auxiliary supply to the AUX+ to AUX- inputs. Observe proper polarity of voltage connection before turning on the auxiliary power supply.

  2. Turn on the auxiliary power supply and verify that the LED (DS1) is on.

  3. Check for the proper output voltages. The output at the VOUT+ and VOUT- ports should be regulated at 12 V (±5%).

  4. Once the proper output voltage is established, connect the load at the VOUT+ and VOUT- ports of the AD-PS3803-RD as illustrated in Figure 9.

Warning

Observe correct polarity of connections to prevent damaging the device.

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Figure 9 AD-PS3803-RD Test Setup using an Auxiliary Power Supply

Demo Setup

Equipment Needed

  • One (1) Programmable DC power supply capable of 60V/3A (DC power supply)

  • One (1) DC2541A PSE controller board (PSE)

  • One (1) RJ45-to-RJ45 Ethernet cable

  • One (1) Digital multimeter (Voltmeter #1)

  • One (1) Electronic load capable of 12V/2A (DC electronic load)

Getting Started

Note

The setup described below uses the DC2541A Demo Board as PSE Controller. Other PSE boards can also be used as alternative, but ensure that the interface and power range is compatible with the AD-PS3803-RD.

  1. Before connecting any power supplies, adjust the DC power supply’s output to 0V and set the current limit to 0.1A.

  2. Turn the supply OFF.

  3. Connect all the equipment, as shown in Figure 1. Do NOT connect the Ethernet cable to AD-PS3803-RD yet.

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    Figure 10 AD-PS3803 Test Setup Diagram

  4. Verify that the electronic load is initially at the OFF position.

  5. Ensure that the indicated jumper position for DC2541A is set correctly, as shown in Table 1 and Figure 3.

Table 2: DC2541A PSE Board Jumper Configuration

PSE Type

Power Mode (JP6)

PORT+ (JP1) / PORT-(JP2)

MID (JP3)

DUALPD (JP4)

LEGACY (JP5)

IEEE 802.3at Type 2 (25.5W)

Type 2 (25.5W)

2-PAIR

LO/HI

LO

LO
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Figure 11 Jumper Connections

Test Measurement

  1. Turn the DC power supply ON and set the voltage to approximately 48V.

  2. Set the DC power supply current limit to 1A.

  3. Connect the RJ45-to-RJ45 Ethernet cable to AD-PS3803-RD, as illustrated in Figure 1.

  4. Turn ON the DC electronic load and set carefully set the current to 2A only.

  5. Check the output voltage reading from Voltmeter #1 and verify that it is within the maximum and minimum limits, as indicated in Table 3.

Table 3: Output Voltage Limits

Assembly

Output Voltage Range (V) [Voltmeter #1]

AD-PS3803-RD

Minimum (V) 11.76

Maximum (V) 12.24

  1. Set the DC power supply voltage to approximately 57V.

  2. Verify that the DC electronic load is still set to the current of 2A.

  3. Check the output voltage reading from Voltmeter #1 and verify that it is within the maximum and minimum limits as indicated in Table 3.

  4. Set the DC electronic load to 0A.

  5. Disconnect the RJ45-to-RJ45 Ethernet cable from AD-PS3803-RD.

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Figure 12 AD-PSD3803 Actual Test Setup

System Performance

Efficiency

Below figure shows the efficiency performance of AD-PS3803-RD at PoE input voltage of 48V and 57V.

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Figure 13 AD-PS3803-RD Efficiency vs. Load Current Performance

Output Regulation

The AD-PS3803-RD maintains within ±5% across its entire output current capability.

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Figure 14 AD-PS3803-RD: Output Voltage vs. Load Current Performance

Resources

Design & Integration Files

Download

AD-PS3803-RD Design & Integration Files

  • Schematic

  • PCB Layout

  • Bill of Materials

  • Allegro Project

  • LTspice Simulation

Help and Support

For questions and more information, please visit the Analog Devices Engineer Zone.