Class 1 Mulitple Output High Efficiency Flyback Converter for PoE Applications Reference Design


Design files


This converter is used for Class 1 PoE applications where high-efficiency and multiple-outputs are required. The multi-outputs for this design are 3.3V/0.7A, 5V/0.145A, 3.3V/1.5A. The flyback converter with synchronous rectifier provides excellent efficiency, and small size for PoE applications, such as an IP phone solution.

The TPS23785B contains both the PoE powered device and the PWM controller functions.

  • Multiple outputs for 3.3V/0.7A, 5V/0.145A, 3.3V/1.5A
  • High efficiency (89%)
  • Isolated flyback with synchronous rectifier
  • Small solution size
  • Uses TPS23785 with PoE interface PD and PWM controller
  • This circuit design is full-functional tested and recommended for new designs.
Output voltage options PMP8752.1 PMP8752.2
Vin (Min) (V) 36 36
Vin (Max) (V) 57 57
Vout (Nom) (V) 3.3 5
Iout (Max) (A) .7 .15
Output Power (W) 2.31 .75
Isolated/Non-Isolated Isolated Isolated
Input Type DC DC
Topology 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

Download ready-to-use system files to speed your design process.


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

SLURA13.PDF (51 K)

Detailed schematic diagram for design layout and components

SLURA14.PDF (140 K)

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

TIDC443.ZIP (314 K)

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


Includes TI products in the design and potential alternatives.

N-channel MOSFETs

CSD17507Q5A30-V, N channel NexFET™ power MOSFET, single SON 5 mm x 6 mm, 10.8 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
Shunt voltage references

TLV431A1% accuracy, low-voltage, adjustable precision shunt regulator

Data sheet: PDF | HTML

Technical documentation

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Type Title Date
Test report PMP8752 Test Results Feb. 01, 2013

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