LT1939 - Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller

Features

  • 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
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LT1939 Typical Application
LT1939 Typical Application
LT1939 Typical Application

Description

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.

Packaging

CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
Drawing
RoHS
LT1939EDD#PBF 3x3 DFN-12 DD E 05-08-1725 Yes
LT1939EDD#TRPBF 3x3 DFN-12 DD E 05-08-1725 Yes
LT1939IDD#PBF 3x3 DFN-12 DD I 05-08-1725 Yes
LT1939IDD#TRPBF 3x3 DFN-12 DD I 05-08-1725 Yes


LT1939 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LT1939EDD#PBF 3x3 DFN-12 E $4.36 $3.05 Yes
LT1939EDD#TRPBF 3x3 DFN-12 E $3.11 Yes
LT1939IDD#PBF 3x3 DFN-12 I $5.23 $3.66 Yes
LT1939IDD#TRPBF 3x3 DFN-12 I $3.72 Yes
Buy NowRequest Samples
* 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 Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1293A LT1939EDD | Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller Contact Factory
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LT1939IDD#PBF 3x3 DFN-12 I $5.23 $3.66 Yes
LT1939IDD#TRPBF 3x3 DFN-12 I $3.72 Yes
Buy NowRequest Samples
* 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 Linear Technology sales office or authorized distributor.

Applications

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

Product Notifications

Please login to your MyLinear account for notifications of datasheet updates, new document releases and LTspice model announcements for your favorite products. If you do not have a MyLinear account you may Sign Up Now.

Forgot your password? Click here.
Need help? Email mylinear@linear.com with questions and comments.

Design Tools

LTspice

LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

To launch a ready to run LTspice demonstration circuit for this part:

  • Step 1: If you have not installed LTspice on this computer, download and install LTspice
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice does not automatically open after clicking the link above, 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

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice:
LT1939

LTpowerCAD

The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD

Design tools for the following parts are available in LTpowerCAD:
LT1939

Technical Support