LT3909 - 2-String × 60mA, 2MHz Step-Up LED Driver with ±2% Current Matching

Features

  • Up to 36V of LEDs, 2-String × 60mA LED Driver
  • Wide Input Range: 2.9V to 40V
  • Up to 40,000:1 PWM Dimming (250ns LED On-Time) (Independent of Leakage at VOUT)
  • ±2% LED Current Matching (Typ ±0.3%)
  • Integrated Schottky Diode
  • Internal 400mΩ, 40V, 1A Switch
  • Single Resistor Sets LED Current (10mA to 60mA) for Both High-Side Current Sources
  • Output Adapts to LED VF for Optimum Efficiency
  • LED Current Regulated Even for VIN > VOUT
  • Fault Flag + Protection for Open-LED and LED-Short-to- GND (Other String Remains in Regulation)
  • Programmable Maximum VOUT (Regulated)
  • Internal Compensation, Soft-Start and Thermal Regulation
  • Accurate EN/UVLO Threshold
  • Fixed 2MHz Switching Frequency

Typical Application

LT3909 Typical Application
LT3909 Typical Application

Description

The LT®3909 is a 2-string × 60mA LED driver with a fixed 2MHz step-up DC/DC converter capable of driving up to 36V of LEDs. Each LED string contains an accurate high-side current source with ±2% current matching. Output voltage adapts to variations in LED VF for optimum efficiency.

Maximum LED current can be programmed from 10mA to 60mA per string using a single resistor. LED brightness can be reduced with analog dimming (up to 10:1) or with PWM dimming (up to 40,000:1 at 100Hz, up to 160:1 at 25kHz) (independent of leakage at VOUT). The LED pins can be paralleled for higher LED current.

Additional features include: programmable maximum VOUT for open LED protection, a fault flag to indicate open-LED or LED-short-to-GND and an internal regulation loop to safely limit junction temperature. The LT3909 also includes internal compensation, internal soft-start and micropower shutdown. The LT3909 is available in the 12-pin (3mm × 3mm) DFN and 12-pin MSOP packages.

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
LT3909EDD#PBF 3x3 DFN-12 DD E 05-08-1725 Yes
LT3909EDD#TRPBF 3x3 DFN-12 DD E 05-08-1725 Yes
LT3909EMSE#PBF MS-12E MSE E 05-08-1666 Yes
LT3909EMSE#TRPBF MS-12E MSE E 05-08-1666 Yes
LT3909IDD#PBF 3x3 DFN-12 DD I 05-08-1725 Yes
LT3909IDD#TRPBF 3x3 DFN-12 DD I 05-08-1725 Yes
LT3909IMSE#PBF MS-12E MSE I 05-08-1666 Yes
LT3909IMSE#TRPBF MS-12E MSE I 05-08-1666 Yes


LT3909 Package Drawing
LT3909 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
LT3909EDD#PBF 3x3 DFN-12 E $3.57 $2.50 Yes
LT3909EDD#TRPBF 3x3 DFN-12 E $2.56 Yes
LT3909EMSE#PBF MS-12E E $3.57 $2.50 Yes
LT3909EMSE#TRPBF MS-12E E $2.56 Yes
LT3909IDD#PBF 3x3 DFN-12 I $3.93 $2.75 Yes
LT3909IDD#TRPBF 3x3 DFN-12 I $2.81 Yes
LT3909IMSE#PBF MS-12E I $3.93 $2.75 Yes
LT3909IMSE#TRPBF MS-12E I $2.81 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
DC2176A LT3909EDD Demo Board | 2-String Boost LED Driver, 7V ≤ VIN ≤ 36V, VLED up to 35V @ 50mA (x2) $199.00
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Click here to view our complete list of demo boards

Applications

  • PDAs, Handheld Computers
  • GPS Receivers
  • Automotive Displays
  • High Contrast Instrument Clusters

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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:

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  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
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Models for the following parts are available in LTspice:
LT3909

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