LT3478 - 4.5A Monolithic LED Drivers with True Color PWM Dimming

Features

  • True Color PWM™ Dimming Delivers Constant LED Color with Up to 3000:1 Range
  • Wide Input Voltage Range: 2.8V to 36V
  • 4.5A, 60mΩ, 42V Internal Switch
  • Drives LEDs in Boost, Buck-Boost or Buck Modes
  • Integrated Resistors for Inductor and LED Current Sensing
  • Program LED Current:
      100mA to 1050mA (LT3478-1)
      (10mV to 105mV)/RSENSE (LT3478)
  • Program LED Current De-Rating vs Temperature
  • Separate Inductor Supply Input
  • Inrush Current Protection
  • Programmable Soft-Start
  • Fixed Frequency Operation from 200kHz to 2.25MHz
  • Open LED Protection (Programmable OVP)
  • Accurate Shutdown/UVLO Threshold with Programmable Hysteresis
  • 16-Pin Thermally Enhanced TSSOP Package
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LT3478 Typical Application
LT3478 Typical Application

Description

The LT3478/LT3478-1 are 4.5A step-up DC/DC converters designed to drive LEDs with a constant current over a wide programmable range. Series connection of the LEDs provides identical LED currents for uniform brightness without the need for ballast resistors and expensive factory calibration.

The LT3478-1 reduces external component count and cost by integrating the LED current sense resistor. The LT3478 uses an external sense resistor to extend the maximum programmable LED current beyond 1A and also to achieve greater accuracy when programming low LED currents. Operating frequency can be set with an external resistor from 200kHz up to 2.25MHz. Unique circuitry allows a PWM dimming range up to 3000:1 while maintaining constant LED color. The LT3478/LT3478-1 are ideal for high power LED driver applications such as automotive TFT LCD backlights, courtesy lighting and heads-up displays. One of two CTRL pins can be used to program maximum LED current. The other CTRL pin can be used to program a reduction in maximum LED current vs temperature to maximize LED usage and improve reliability.

Additional features include inrush current protection, programmable open LED protection and programmable soft-start. Each part is available in a 16-pin thermally enhanced TSSOP Package.

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
LT3478EFE-1#PBF TSSOP-16 FE E 05-08-1663 (BC) Yes
LT3478EFE-1#TRPBF TSSOP-16 FE E 05-08-1663 (BC) Yes
LT3478EFE#PBF TSSOP-16 FE E 05-08-1663 (BC) Yes
LT3478EFE#TRPBF TSSOP-16 FE E 05-08-1663 (BC) Yes
LT3478IFE-1#PBF TSSOP-16 FE I 05-08-1663 (BC) Yes
LT3478IFE-1#TRPBF TSSOP-16 FE I 05-08-1663 (BC) Yes
LT3478IFE#PBF TSSOP-16 FE I 05-08-1663 (BC) Yes
LT3478IFE#TRPBF TSSOP-16 FE I 05-08-1663 (BC) Yes


LT3478 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
LT3478EFE-1#PBF TSSOP-16 E $5.14 $3.60 Yes
LT3478EFE-1#TRPBF TSSOP-16 E $3.66 Yes
LT3478EFE#PBF TSSOP-16 E $5.14 $3.60 Yes
LT3478EFE#TRPBF TSSOP-16 E $3.66 Yes
LT3478IFE-1#PBF TSSOP-16 I $6.17 $4.32 Yes
LT3478IFE-1#TRPBF TSSOP-16 I $4.38 Yes
LT3478IFE#PBF TSSOP-16 I $6.17 $4.32 Yes
LT3478IFE#TRPBF TSSOP-16 I $4.38 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
DC949A-A LT3478EFE-1 Demo Board | Boost LED Driver, Internal RSENSE, 2.8V ≤ VIN ≤ 25V, VLED up to 36V @ 350mA $125.00
DC949A-B LT3478EFE Demo Board | Boost LED Driver, Adj LED Current, 2.8V ≤ VIN ≤ 25V, VLED up to 36V @ 350mA $125.00
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
LT3478IFE-1#PBF TSSOP-16 I $6.17 $4.32 Yes
LT3478IFE-1#TRPBF TSSOP-16 I $4.38 Yes
LT3478IFE#PBF TSSOP-16 I $6.17 $4.32 Yes
LT3478IFE#TRPBF TSSOP-16 I $4.38 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

  • High Power LED Driver
  • Automotive Lighting

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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:
LT3478
LT3478-1

Technical Support