WHITE LED STEP-UP CONVERTER

LM1937

FEATURES

• Inherently Matched LED Current

• High Efficiency: 84% Typical

• Drives Up to Four LEDs from a 3.2V Supply

• Drives Up to Six LEDs from a 5V Supply

• 36V Rugged Bipolar Switch

• Fast 1.2MHz Switching Frequency

• Uses Tiny 1mm Tall Inductors

• Requires Only 0.22µF Output Capacitor

• Moisture Sensitivity Level 3

APPLICATIONS

• Cellular Phones

• PDAs, Handheld Computers

• Digital Cameras

• MP3 Players

• GPS Receivers

ORDERING INFORMATION

DESCRIPTION

TYPICAL APPLICATION CIRCUIT

Figure 1. Li-Ion Powered Driver for Three White LEDs

Jul. 2010 - Rev. 1.1.1

HTC

- 1 -

Package

Marking

Device

LM1937SF5

1937

SOT-23 5L

The LM1937 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current.

The device can drive two, three or four LEDs in series from a Li-Ion cell. Series connection of the LEDs

provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors.

The output capacitor can be as small as 0.22µF, saving space versus alternative solutions. A low 95mV

feedback voltage minimizes power loss for better efficiency.

SOT-23 5L (SOT-25)

1.SW 2.GND 3.FB 4.SHDN 5.VIN