Class 3 - Mulitple Output, High Efficiency Driven Flyback Converter for PoE Applications


Design files


This converter is used for Class 3 PoE applications where high efficiency and multiple outputs are required. The flyback converter with synchronous rectifier provides excellent efficiency and small size for PoE applications such as IP Phones. The TPS23785B contains both the PoE Powered Device and the PWM controller functions.

  • High efficiency (90%)
  • Multiple outputs for 10V/0.2A, 5V/1A, 3.3V/1.5A
  • Isolated Flyback with synchornous rectifier
  • Small size solution
  • Uses TPS23785 with PoE interface PD and PWM controller
  • This circuit design is full-functional tested and recommended for new designs.
Output voltage options PMP8408.1 PMP8408.2 PMP8408.3
Vin (Min) (V) 36 36 36
Vin (Max) (V) 57 57 57
Vout (Nom) (V) 3.3 5 10
Iout (Max) (A) 1.5 1 .2
Output Power (W) 4.95 5 2
Isolated/Non-Isolated Isolated Isolated Isolated
Input Type DC DC DC
Topology Flyback- Synchronous^POE Flyback- Synchronous^POE Flyback- Synchronous^POE
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A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products

Design files

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SLUUA89.PDF (1933 K)

Test results for the reference design, including efficiency graphs, test prerequisites and more

SLURA09.PDF (55 K)

Detailed schematic diagram for design layout and components

SNVR184.PDF (102 K)

Detailed schematic diagram for design layout and components

SLURA10.PDF (140 K)

Complete listing of design components, reference designators, and manufacturers/part numbers

TIDC430.ZIP (314 K)

Design file that contains information on physical board layer of design PCB


Includes TI products in the design and potential alternatives.


CSD18533Q5A60-V, N channel NexFET™ power MOSFET, single SON 5 mm x 6 mm, 5.9 mOhm

Data sheet: PDF | HTML
Powered devices

TPS23785BHigh-Power, High-Efficiency PoE PD and DC-to-DC Controller

Data sheet: PDF
Shunt voltage references

TL431Adjustable precision shunt regulator

Data sheet: PDF | HTML

Technical documentation

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Type Title Date
Test report PMP8408 Test Results Jan. 18, 2013

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