RD-169: 30mA @ 21V Max, 8 ~ 16 Vin

Summary

The reference design, with National Semiconductor’s LM3431 three-channel, constant-current LED driver, uses two strings of six series-connected LEDs at a current of 30 mA per string. Each LED has a forward voltage drop of about 3.5V, making the total voltage across each string between 21V and 27V. With a 12V power source, the LM3431 is configured as a boost converter to generate this 21V to 27V output voltage.

The design also includes a circuit utilizing a photodiode to make the brightness of the LEDs proportional to ambient light thus improving the readability of the display under all lighting conditions.

Specifications

Manufacturer Texas Instruments
Category Lighting
Sub-Category LED Drivers - DC In
Eval Board Board not Stocked
Voltage In 8 ~ 16 V
Topology Step Up
Current Out 30 mA
Voltage Out (Max) 21 V
Outputs and Type 2 Non-Isolated
Efficiency @ Conditions >75%, 8 ~ 16V in, 2 x 21V @ 30 mA
Features Ambient Light Adaptive
Dimming Control
Switching Frequency 500 kHz
Component Count + Extras 47 + 6
Design Author Texas Instruments
Application / Target Market LCD Backlighting
Main I.C. Base Part LM3431
Date Created By Author
Date Added To Library 2011-03

Support Documents & Media

RD-169 - User Guide LM3431 - Datasheet Ultra Librarian Software:CAD Symbols and Footprints (Zip File) TI's CAD/CAE Symbols and Footprint Search

Media

RD_169__Schematic.JPG RD_169__Board.JPG