MIC3291

1.2MHz PWM White LED Driver

with Internal Schottky Diode and

Single-Wire Linear Brightness

Control

MLF and MicroLead Frame are registered trademarks of Amkor Technologies, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose,

CA 95131 • USA • tel +1 (

September 2010

M9999-092810

(408) 944-0800

General Description

The MIC3291 is a PWM switching boost regulator that is

optimized for constant current white LED (WLED) driver

applications. The MIC3291 features an internal Schottky

diode, allowing an efficient DC/DC solution that requires

only four external components.

The MIC3291 allows for a single-wire simple digital

interface to control the dimming over 16 steps with a linear

scale. The preprogramming feature allows the user to

select any one of the 16 WLED current levels as the start

up brightness level.

The feedback voltage of the MIC3291 is only 250mV,

allowing high efficiency while retaining excellent accuracy

for the WLED current.

The MIC3291 implements a constant frequency 1.2MHz

PWM control scheme. The high frequency PWM operation

saves board space by reducing external component sizes.

The 1.2MHz PWM scheme also reduces switching noise

and ripple to the input power source.

The 2.5V to 6.5V input voltage range of the MIC3291

allows direct operation from single cell Li-Ion as well as 3

to 4 cell NiCad/NiMH/Alkaline batteries. Battery life is

preserved with a low 1µA shutdown current.

The MIC3291 is available in a low profile Thin SOT23 6-

pin and 2mm × 2mm MLF

temperature range of –40

°C to +125°C.

Data sheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• Single wire combines 16 level linear brightness and

shutdown control

• 18V / 25V OVP options supports up to four and six

WLEDs

• Startup in any one of 16 brightness levels

• Internal Schottky diode

• 2.5V to 6.5V input voltage

• 1.2MHz PWM operation

• Over 500mA switch current

• 250mV reference voltage

• ±5% LED current accuracy

• <1µA shutdown current

• UVLO and over-temperature protection

• Thin SOT23-6L package option

Applications

• Mobile handsets

• LCD handset backlighting

• Digital cameras

• Portable media players/MP3 players

• Portable applications

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Typical Application

White LED Driver with OVP and Digital Control