Features and Benefits

  • Drives External Power MOSFET with External ISENSE Resistor
  • Application Input Voltage Limited Only by External Power Components
  • Senses Output Voltage Directly from Primary Side Winding—No Optoisolator Required
  • Accurate Regulation Without User Trims
  • Regulation Maintained Well into Discontinuous Mode
  • Switching Frequency from 50kHz to 250kHz with External Capacitor
  • Optional Load Compensation
  • Optional Undervoltage Lockout
  • Available in 16-Pin SO and SSOP Packages

Product Details

The LT1725 is a monolithic switching regulator controller specifically designed for the isolated flyback topology. It drives the gate of an external MOSFET and is generally powered from a third transformer winding. These features allow for an application input voltage limited only by external power path components. The third transformer winding also provides output voltage feedback information, such that an optoisolator is not required. Its gate drive capability coupled with a suitable external MOSFET can deliver load power up to tens of watts.

The LT1725 has a number of features not found on most other switching regulator ICs. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regulation well into discontinuous mode in most applications. Optional load compensation circuitry allows for improved load regulation. An optional undervoltage lockout pin halts operation when the application input voltage is too low. An optional external capacitor implements a soft-start function. A 3V output is available at up to several mA for powering primary side application circuitry.


  • Telecom Isolated Converters
  • Offline Isolated Power Supplies
  • Instrumentation Power Supplies

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (8)

Tools & Simulations


LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.


Models for the following parts are available in LTspice:


Product Recommendations

LT1725 Companion Parts

Recommended µModule Regulator

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.


LT1725 Didn't find what you were looking for? Ask the Analog community »

Sample & Buy

Sample & Buy functionality exists in desktop site
Check Inventory

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

Price Table Help


Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.