MAXREFDES1022: 5V/2A, Synchronous No-Opto Isolated Flyback DC-DC Converter


Reference Design Disclaimer See the  Important Notice and Disclaimer  covering reference designs and other Maxim resources.


Due to its simplicity and low cost, the flyback converter is the preferred choice for low-to-medium isolated DC-DC power-conversion applications. However, the use of an optocoupler or an auxiliary winding on the flyback transformer for voltage feedback across the isolation barrier increases the number of components and design complexity. The MAX17690 eliminates the need for an optocoupler or auxiliary transformer winding and achieves ±5% output voltage regulation over line, load, and temperature variations.

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.

An isolated no-opto flyback DC-DC converter using the MAX17690 and MAX17606 is demonstrated for a 5V DC output application. The power supply delivers up to 2A at 5V.


  • 4.5V 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 x 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


Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 10 50 2 - 5 10 Isolated Flyback


Input Type DC
Vin(Min) 10
Vin(Max) 50
Iout(Max) 2
Single/Multiple Output -
Vout(V) 5
Pout(W) 10
Isolated/Non-Isolated Isolated
Topology Flyback

Maxim Devices (1)

Part Number Name Product Family Order Design kits and evaluation modules
MAX17690 60V, No-Opto Isolated Flyback Controller Isolated Power Buy Now Design Kits

Maxim Devices (1)

Part Number Product Family
Isolated Power
60V, No-Opto Isolated Flyback Controller

Design Files (3)

Title Type Size Date
maxrefdes1022-pcb PDF 2MB 2019-07-09
maxrefdes1022-schematic PDF 90KB 2019-07-09
maxrefdes1022-bom PDF 213KB 2019-07-09
Date Type


(PDF, 2MB)



(PDF, 90KB)



(PDF, 213KB)

MAXREFDES1022 Related Videos

View All Videos