1. Products
  2. Power Management
  3. Switching Regulators
  4. Multitopology DC/DC
  5. LT1939


Features and Benefits

  • Wide Input Range: 3V to 25V
  • Short-Circuit Protected Over Full Input Range
  • 2A Output Current Capability
  • Adjustable/Synchronizable Fixed Frequency Operation from 250kHz to 2.2MHz
  • Soft-Start/Tracking Capability
  • Output Adjustable Down to 0.8V
  • Adjustable Linear Regulator/Driver with 13mA Output Capability
  • Power Good Comparator with Complementary Outputs
  • Low Shutdown Current: 12μA
  • Thermally Enhanced 3mm × 3mm DFN Package

Product Details

The LT1939 is a current mode PWM step-down DC/DC converter with an internal 2.3A switch. The wide input range of 3V to 25V makes the LT1939 suitable for regulating power from a wide variety of sources, including automotive batteries, industrial supplies and unregulated wall adapters.

Resistor-programmable 250kHz to 2.2MHz frequency range and synchronization capability enable optimization between efficiency and external component size. Cycle-by-cycle current limit, frequency foldback and thermal shutdown provide protection against a shorted output. The soft-start feature controls the ramp rate of the output voltage, eliminating input current surge during start-up, and also provides output tracking.

The LT1939 contains an internal NPN transistor with feedback control which can be configured as a linear regulator or as a linear regulator controller.

The LT1939’s low current shutdown mode (<12μA) enables easy power management in battery-powered systems.


  • Automotive Battery Regulation
  • Industrial Control
  • Wall Transformer Regulation
  • Distributed Power Regulation

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 (1)

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.

To launch ready-to-run LTspice demonstration circuits for this part:

Step 1: Download and install LTspice on your computer.

Step 2: Click on the link in the section below to download a demonstration circuit.

Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.


Models for the following parts are available in LTspice:


Product Recommendations

LT1939 Companion Parts

Recommended Related Parts

Recommended Suggested Oscillator

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.View our quality and reliability program and certifications for more information.

Part Number Material Declaration Reliability Data Pin/Package Drawing CAD Symbols, Footprints & 3D Models
LT1939EDD#PBF Material Declaration Reliability Data 12-Lead DFN (3mm x 3mm w/ EP)
LT1939EDD#TRPBF Material Declaration Reliability Data 12-Lead DFN (3mm x 3mm w/ EP)
LT1939IDD#PBF Material Declaration Reliability Data 12-Lead DFN (3mm x 3mm w/ EP)
LT1939IDD#TRPBF Material Declaration Reliability Data 12-Lead DFN (3mm x 3mm w/ EP)
Wafer Fabrication Data R530 Reliability Data

Sample & Buy

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Buy Now Pricing

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List Pricing

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Price Table Help


Evaluation Boards

Pricing displayed is based on 1-piece.

Up to two boards can be purchased through Analog.com. To order more than two, please purchase through one of our listed distributors.

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.