MAXREFDES1175: PoE Powered Device and 5V/1.4A No-Opto Flyback DC-DC Converter Using the MAX17690 and MAX5969B


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Power over Ethernet (PoE) is a technology that allows network cables to deliver power to a powered device (PD) through power-sourcing equipment (PSE) or midspan, and has many advantages over traditional methods of delivering power. PoE allows power and data to be combined, removing the need for altering the AC mains infrastructure and can be installed by non-electricians. PoE is an intelligent system designed with protection at the forefront, preventing overload, underpowering, and installation errors, while allowing simple scalability and reliability.

The MAX17690 implements an innovative algorithm to accurately determine the output voltage by sensing the reflected voltage across the primary winding during the flyback time interval. By sampling and regulating this reflected voltage when the secondary current is close to zero, the effects of secondary-side DC losses in the transformer winding, the PCB tracks, and the rectifying diode on output voltage regulation can be minimized. The MAX17690 also compensates for the negative temperature coefficient of the rectifying diode.


  • IEEE 802.3af/at Compliance
  • Thermally Enhanced, 3mm × 3mm, 10-Pin TDFN Package (MAX5969B)
  • 30V to 60V Input Voltage Range
  • Programmable Switching Frequency from 50kHz to 250kHz
  • Programmable Input Enable/UVLO Feature
  • Programmable Input Overvoltage Protection
  • Adjustable Soft-Start
  • 2A/4A Peak Source/Sink Gate Drive Capability
  • Hiccup Mode Short-Circuit Protection
  • Fast Cycle-by-Cycle Peak Current Limit
  • Thermal Shutdown Protection
  • Space-Saving, 16-Pin, 3mm × 3mm TQFN Package
  • -40°C to +125°C Operating Temperature Range


Designed, Built, Tested

Board pictured here has been fully assembled and tested. Not available for sale.



PCB Layout

Bill of Materials

Test Results


Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 30 60 1.4 - 5 7 Isolated Flyback


Input Type DC
Vin(Min) 30
Vin(Max) 60
Iout(Max) 1.4
Single/Multiple Output -
Vout(V) 5
Pout(W) 7
Isolated/Non-Isolated Isolated
Topology Flyback

Maxim Devices (2)

Part Number Name Product Family Order Design kits and evaluation modules
MAX5969B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Complete System Power Protection IC Buy Now Design Kits
MAX17690 60V, No-Opto Isolated Flyback Controller Isolated Power Buy Now Design Kits

Maxim Devices (2)

Part Number Product Family
Complete System Power Protection IC
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET
Isolated Power
60V, No-Opto Isolated Flyback Controller

Design Files (4)

Title Type Size Date
TTS MAXREFDES Test Results Template_Rev 0_0318 PDF 349KB 2019-01-25
maxrefdes1175-schematic PDF 24KB 2019-01-25
maxrefdes1175-pcb PDF 2MB 2019-01-25
maxrefdes1175-bom PDF 104KB 2019-01-25
Date Type

TTS MAXREFDES Test Results Template_Rev 0_0318

(PDF, 349KB)



(PDF, 24KB)



(PDF, 2MB)



(PDF, 104KB)

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