MAXREFDES1194: Five-Output, No-Opto Flyback DC-DC Converter Using the MAX17690


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The MAXREFDES1194 is a no-opto flyback DC-DC power supply that delivers five outputs from a 6V to 60V supply voltage. It is designed for equipment that needs multichannel, isolated power supplies with a wide input voltage range.

The MAXREFDES1194 employs the no-opto flyback control technique of the MAX17690. This document explains how the MAX17690 peak current-mode PWM converter can be used to generate five isolated outputs from a 6V to 60V input voltage. An overview of the design specification is shown above.

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.


  • 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.



Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 6 60 0.3 - 3 1.084 Isolated No-Opto Flyback


Input Type DC
Vin(Min) 6
Vin(Max) 60
Iout(Max) 0.3
Single/Multiple Output -
Vout(V) 3
Pout(W) 1.084
Isolated/Non-Isolated Isolated
Topology No-Opto 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 (6)

Title Type Size Date
MAXREFDES1194-PCB PDF 129KB 2019-07-09
MAXREFDES1194-schematic PDF 436KB 2019-07-09
maxrefdes1194-pcb PDF 479KB 2019-08-27
maxrefdes1194-schematic PDF 21KB 2019-08-27
maxrefdes1194-bom PDF 1MB 2019-07-09
TTS MAXREFDES Test Results Template_Rev 0_0318 PDF 191KB 2019-07-09
Date Type


(PDF, 129KB)



(PDF, 436KB)



(PDF, 479KB)



(PDF, 21KB)



(PDF, 1MB)


TTS MAXREFDES Test Results Template_Rev 0_0318

(PDF, 191KB)

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