MAXREFDES1253: Miniature 17V, 0.75A No Opto Flyback DC to DC Converter Using the MAX17690


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The MAXREFDES1253 is a no-opto flyback converter that delivers up to 0.75A at 17V from a 18V to 54V supply voltage. It is designed for industrial equipment that needs isolated voltage from wide input supply voltage.

The MAXREFDES1253 illustrates techniques using the no-opto flyback converter to generate isolated output. This document explains how the MAX17690 no-opto flyback converter can be used to generate 17V from 18V to 54V input voltage.

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.




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PCB Layout


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Test Results


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Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 18 54 0.75 Single 17 12.75 Isolated No-Opto Flyback


Input Type DC
Vin(Min) 18
Vin(Max) 54
Iout(Max) 0.75
Single/Multiple Output Single
Vout(V) 17
Pout(W) 12.75
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

Maxim Devices (1)

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

Design Files (4)

Title Type Size Date
MAXREFDES1253 BOM CSV 4KB 2021-11-21
MAXREFDES1253 PCB Layout PDF 660KB 2021-06-26
MAXREFDES1253 Schematic PDF 16KB 2021-11-21
MAXREFDES1253 Test Results PDF 132KB 2021-11-21
Date Type


(CSV, 4KB)



(PDF, 660KB)


MAXREFDES1253 Schematic

(PDF, 16KB)


MAXREFDES1253 Test Results

(PDF, 132KB)

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