LT3957 - Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch


  • Wide Input Voltage Range: 3V to 40V
  • Single Feedback Pin for Positive or Negative Output Voltage
  • Internal 5A/40V Power Switch
  • Current Mode Control Provides Excellent Transient Response
  • Programmable Operating Frequency (100kHz to 1MHz) with One External Resistor
  • Synchronizable to an External Clock
  • Low Shutdown Current < 1μA
  • Internal 5.2V Low Dropout Voltage Regulator
  • Programmable Input Undervoltage Lockout with Hysteresis
  • Programmable Soft-Start
  • Thermally Enhanced QFN (5mm × 6mm) Package

Typical Application

LT3957 Typical Application
LT3957 Typical Application


The LT3957 is a wide input range, current mode DC/DC converter which is capable of generating either positive or negative output voltages. It can be configured as either a boost, flyback, SEPIC or inverting converter. It features an internal low side N-channel power MOSFET rated for 40V at 5A and driven from an internal regulated 5.2V supply. The fixed frequency, current-mode architecture results in stable operation over a wide range of supply and output voltages.

The operating frequency of LT3957 can be set with an external resistor over a 100kHz to 1MHz range, and can be synchronized to an external clock using the SYNC pin. A minimum operating supply voltage of 3V, and a low shutdown quiescent current of less than 1μA, make the LT3957 ideally suited for battery-powered systems.

The LT3957 features soft-start and frequency foldback functions to limit inductor current during start-up.

LT3957 -
LT3957A Improved Load Transient Performance 


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
LT3957EUHE#PBF 5x6 QFN-36 UHE E 05-08-1836 Yes
LT3957EUHE#TRPBF 5x6 QFN-36 UHE E 05-08-1836 Yes
LT3957IUHE#PBF 5x6 QFN-36 UHE I 05-08-1836 Yes
LT3957IUHE#TRPBF 5x6 QFN-36 UHE I 05-08-1836 Yes

LT3957 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
LT3957EUHE#PBF 5x6 QFN-36 E $4.22 $2.95 Yes
LT3957EUHE#TRPBF 5x6 QFN-36 E $3.01 Yes
LT3957IUHE#PBF 5x6 QFN-36 I $4.84 $3.39 Yes
LT3957IUHE#TRPBF 5x6 QFN-36 I $3.45 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
DC1544A LT3957EUHE Demo Board | Boost, 4.5V ≤ VIN ≤ 20V, Vout = 24V @ 0.6A $175.00
Buy Now
Click here to view our complete list of demo boards


  • Automotive
  • Telecom
  • Industrial

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 with questions and comments.

Design Tools


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:

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

Models for the following parts are available in LTspice:


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:

Technical Support