LT3474/LT3474-1 - Step-Down 1A LED Driver

Features

  • True Color PWM Delivers Constant Color with 400:1 Dimming Range
  • Wide Input Range: 4V to 36V
  • Up to 1A LED Current
  • Adjustable 200kHz–2MHz Switching Frequency
  • Adjustable Control of LED Current
  • Integrated Boost Diode
  • High Output Current Accuracy is Maintained Over a Wide Range from 35mA to 1A
  • Open LED (LT3474) and Short-Circuit Protection
  • High Side Sense Allows Grounded Cathode Connection
  • Uses Small Inductors and Ceramic Capacitors
  • LT3474-1 Drives LED Strings Up to 26V
  • Compact 16-Lead TSSOP Thermally Enhanced Surface Mount Package
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LT3474 Typical Application
LT3474 Typical Application

Description

The LT3474/LT3474-1 are fixed frequency step-down DC/DC converters designed to operate as constant-current sources. An internal sense resistor monitors the output current allowing accurate current regulation, ideal for driving high current LEDs. High output current accuracy is maintained over a wide current range, from 35mA to 1A, allowing a wide dimming range.

Unique PWM circuitry allows a dimming range of 400:1, avoiding the color shift normally associated with LED current dimming.

The high switching frequency offers several advantages, permitting the use of small inductors and ceramic capacitors. Small inductors combined with the 16 lead TSSOP surface mount package save space and cost versus alternative solutions. The constant switching frequency combined with low-impedance ceramic capacitors result in low, predictable output ripple.

With their wide input range of 4V to 36V, the LT3474/ LT3474-1 regulate a broad array of power sources, from 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies. A current mode PWM architecture provides fast transient response and cycle-by-cycle current limiting. Frequency foldback and thermal shutdown provide additional protection.

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
LT3474EFE-1#PBF TSSOP-16 FE E 05-08-1663 (BA) Yes
LT3474EFE-1#TRPBF TSSOP-16 FE E 05-08-1663 (BA) Yes
LT3474EFE#PBF TSSOP-16 FE E 05-08-1663 (BA) Yes
LT3474EFE#TRPBF TSSOP-16 FE E 05-08-1663 (BA) Yes
LT3474IFE-1#PBF TSSOP-16 FE I 05-08-1663 (BA) Yes
LT3474IFE-1#TRPBF TSSOP-16 FE I 05-08-1663 (BA) Yes
LT3474IFE#PBF TSSOP-16 FE I 05-08-1663 (BA) Yes
LT3474IFE#TRPBF TSSOP-16 FE I 05-08-1663 (BA) Yes


LT3474 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
LT3474EFE-1#PBF TSSOP-16 E $4.22 $2.95 Yes
LT3474EFE-1#TRPBF TSSOP-16 E $3.01 Yes
LT3474EFE#PBF TSSOP-16 E $4.21 $2.95 Yes
LT3474EFE#TRPBF TSSOP-16 E $3.07 Yes
LT3474IFE-1#PBF TSSOP-16 I $5.06 $3.54 Yes
LT3474IFE-1#TRPBF TSSOP-16 I $3.60 Yes
LT3474IFE#PBF TSSOP-16 I $5.06 $3.54 Yes
LT3474IFE#TRPBF TSSOP-16 I $3.66 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
DC1309A LT3474EFE-1 Demo Board | Buck LED Driver, 4 ≤ VIN ≤ 36V, VLED up to 26V @ 1A $100.00
DC842A LT3474EFE/IFE Demo Board | Step-Down LED Driver, 6V ≤ VIN ≤ 36V, VLED = 3.9V @ 1A $100.00
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
LT3474IFE-1#PBF TSSOP-16 I $5.06 $3.54 Yes
LT3474IFE-1#TRPBF TSSOP-16 I $3.60 Yes
LT3474IFE#PBF TSSOP-16 I $5.06 $3.54 Yes
LT3474IFE#TRPBF TSSOP-16 I $3.66 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 and Avionic Lighting
  • Architectural Detail Lighting
  • Display Backlighting
  • Constant Current Sources

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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:
LT3474
LT3474-1

Technical Support