MAXREFDES1002: 6W, Synchronous No-Opto Flyback DC-DC Converter


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The MAX17690 is a peak current mode, fixed-frequency switching controller specifically designed for the isolated flyback topology operating in Discontinuous Conduction Mode (DCM). The device senses the isolated output voltage directly from the primary-side flyback waveform during the off-time of the primary switch. No auxiliary winding or optocoupler is required for output voltage regulation. 

The MAX17690 is designed to operate over a wide supply range from 4.5V to 60V. The switching frequency is programmable from 50kHz to 250kHz. The MAX17690 provides an input overvoltage protection through the OVI pin. The 7V internal LDO output of the MAX17690 makes it suitable for switching both logic-level and standard MOSFETs used in flyback converters. With 2A/4A source/ sink currents, the MAX17690 is ideal for driving low RDS(ON) power MOSFETs with fast gate transition times. The MAX17690 provides an adjustable soft-start feature to limit the inrush current during startup. 

The MAX17690 provides temperature compensation for the output diode forward-voltage drop. The MAX17690 has robust hiccup-protection and thermal protection schemes, and is available in a space-saving 3mm x 3mm 16-pin TQFN package with a temperature range from -40℃ to +125℃. 

A no-opto flyback DC-DC converter using the MAX17690 is demonstrated for a 12V DC output application. The power supply delivers up to 0.5A at 12V.


  • No Optocoupler or Third Winding Required
  • 2A/4A Peak Source/Sink Gate Drive Currents
  • 50kHz to 250kHz Programmable Switching Frequency
  • Input EN/UVLO Feature
  • Input Overvoltage Protection
  • Programmable Soft-Start
  • Hiccup-Mode Short-Circuit Protection
  • Thermal Shutdown Protection
  • -40℃ to +125℃ Operating Temperature Range
  • Space-Saving, 3mm x 3mm, 16-Pin TQFN Package


Designed, Built, Tested

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



PCB Layout

Test Results


Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 18 36 0.5 - 12 6 Isolated Flyback


Input Type DC
Vin(Min) 18
Vin(Max) 36
Iout(Max) 0.5
Single/Multiple Output -
Vout(V) 12
Pout(W) 6
Isolated/Non-Isolated Isolated
Topology Flyback

Maxim Devices (1)

Part Number Name Product Family Order Design kits and evaluation modules
MAX17606 Secondary-Side Synchronous MOSFET Driver for Flyback Converters Isolated Power Buy Now Design Kits

Maxim Devices (1)

Part Number Product Family
Isolated Power
Secondary-Side Synchronous MOSFET Driver for Flyback Converters

Design Files (7)

Title Type Size Date
refdes1002-test-results-load-transient PDF 174KB 2018-03-19
maxrefdes1002-pcb PDF 2MB 2019-07-09
refdes1002-test-results-kgd PDF 128KB 2019-07-09
MAXREFDES1002_MAX17690_BOM_apps_p1 PDF 222KB 2019-07-09
maxrefdes1002-schematic PDF 90KB 2019-07-09
refdes1002-test-results-output-ripple PDF 518KB 2019-07-09
REFDES1002-TestResults PDF 727KB 2019-07-09
Date Type


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