LT3740 - Wide Operating Range, Valley Mode, No RSENSE Synchronous Step-Down Controller

Features

  • Wide VIN Range: 2.2V to 22V
  • Internal Boost Provides 6V Gate Drive For VIN Down to 2.2V
  • No Sensing Resistor Required
  • Dual N-Channel MOSFET Synchronous Drive
  • Valley Current Mode Control
  • Optimized for High Step-Down Ratio
  • Power Good Output Voltage Monitor
  • 0.8V Reference
  • Three Pin-Selected Current Limit Levels
  • Constant Switching Frequency: 300kHz
  • Programmable Soft-Start
  • Output Voltage Tracking
  • Available in 16-Pin 5mm × 3mm DFN

Typical Application

LT3740 Typical Application
LT3740 Typical Application

Description

The LT3740 is a synchronous step-down switching regulator controller that drives N-channel power MOSFET stages. The controller uses valley current mode architecture to achieve very low duty cycles with excellent transient response without requiring a sense resistor.

The LT3740 includes an internal step-up converter to provide a bias 7.8V higher than the input voltage for the drive. This enables the part to work from an input voltage as low as 2.2V.

The XREF pin is an external reference input that allows the user to override the internal 0.8V feedback reference with any lower value, allowing full control of the output voltage during operation, output voltage tracking or soft-start.

The LT3740 has three current limit levels that can be chosen by connecting the RANGE pin to ground, open, and input respectively.

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
LT3740EDHC#PBF 5x3 DFN-16 DHC E 05-08-1706 Yes
LT3740EDHC#TRPBF 5x3 DFN-16 DHC E 05-08-1706 Yes


LT3740 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
LT3740EDHC#PBF 5x3 DFN-16 E $2.96 $1.95 Yes
LT3740EDHC#TRPBF 5x3 DFN-16 E $2.01 Yes
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* 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
DC947A LT3740EDHC Demo Board $125.00
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Click here to view our complete list of demo boards

Applications

  • Notebook and Palmtop Computers, PDA
  • Portable Instruments
  • Distributed Power Systems

Product Notifications

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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:
LT3740

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:
LT3740

Technical Support