LT3743 - High Current Synchronous Step-Down LED Driver with Three-State Control

Features

  • PWM Dimming Provides Up to 3000:1 Dimming Ratio
  • CTRL_SEL Dimming Provides Up to 3000:1 Dimming Ratio Between Any Current
  • Three-State Current Control for Color Mixing
  • ±6% Current Regulation Accuracy
  • 6V to 36V Input Voltage Range
  • Average Current Mode Control
  • 2μs Maximum Recovery Time Between Any Current Regulation State
  • <1μA Shutdown Current
  • Output Voltage Regulation and Open-LED Protection
  • Thermally Enhanced 4mm × 5mm QFN and 28-Pin FE Package

Typical Application

LT3743 Typical Application
LT3743 Typical Application

Description

The LT®3743 is a fixed frequency synchronous step-down DC/DC controller designed to drive high current LEDs. The average current mode controller will maintain inductor current regulation over a wide output voltage range of 0V to (VIN – 2V). LED dimming is achieved through analog dimming on the CTRL_L, CTRL_H and CTRL_T pins and with PWM dimming on the PWM and CTRL_SEL pins. Through the use of externally switched load capacitors, the LT3743 is capable of changing regulated LED current levels within several μs, providing accurate, high speed PWM dimming between two current levels. The switching frequency is programmable from 200kHz to 1MHz through an external resistor on the RT pin.

Additional features include voltage regulation and overvoltage protection set with a voltage divider from the output to the FB pin. Overcurrent protection is provided and set by the CTRL_H pin.

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
LT3743EFE#PBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LT3743EFE#TRPBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LT3743EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LT3743EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LT3743IFE#PBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LT3743IFE#TRPBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LT3743IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LT3743IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes


LT3743 Package Drawing
LT3743 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
LT3743EFE#PBF TSSOP-28 E $7.07 $4.95 Yes
LT3743EFE#TRPBF TSSOP-28 E $5.01 Yes
LT3743EUFD#PBF 4x5 QFN-28 E $6.86 $4.80 Yes
LT3743EUFD#TRPBF 4x5 QFN-28 E $4.86 Yes
LT3743IFE#PBF TSSOP-28 I $8.31 $5.82 Yes
LT3743IFE#TRPBF TSSOP-28 I $5.88 Yes
LT3743IUFD#PBF 4x5 QFN-28 I $8.07 $5.65 Yes
LT3743IUFD#TRPBF 4x5 QFN-28 I $5.71 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
DC1470A LT3743EUF Demo Board | High Current Step-Down LED Driver Controller, 6.5V ≤ VIN ≤ 24V, VLED = 6V @ 20A $175.00
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Click here to view our complete list of demo boards

Applications

  • DLP Projectors
  • High Power Architectural Lighting
  • Laser Diodes

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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:
LT3743

Technical Support