MIC3289

1.2MHz PWM White LED Driver with

Internal Schottky Diode and True 1-Wire

Digital Control

MicroLead Frame and MLF are registered trademarks of Amkor Technologies.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (

June 2007

M9999-061807

(408) 944-0800

General Description

The MIC3289 is a PWM boost-switching regulator that is

optimized

for

constant-current

white

LED

driver

applications. The MIC3289 features an internal Schottky

diode, allowing an efficient DC/DC solution that requires

only 4 external components.

The MIC3289 allows for a single wire simple digital

interface to control the dimming over 16 steps with a log

scale to give better resolution at the lower currents and to

better match the sensitivity of the human eye. The pre-

programming 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 MIC3289 is only 250mV,

allowing high efficiency while retaining excellent accuracy

for the white LED current.

The MIC3289 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 MIC3289 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 MIC3289 is available in a low profile Thin SOT23 6-

lead package and a 2mm × 2mm MLF

has a junction 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 logarithmic brightness &

shutdown control

• 16V / 24V OVP options supports up to 4 & 6 WLEDs

• Start-up in any one of 16 brightness levels

• Internal Schottky diode

• 2.5V to 6.5V input voltage

• 1.2 MHz PWM operation

• Over 500mA switch current

• 250mV reference voltage

• ±5% LED current accuracy

• <1µA shutdown current

• Over temperature protection

• UVLO

• Thin SOT23-6L package option

• 2mm × 2mm leadless MLF

• –40

Applications

• White/Blue LED driver for backlighting

-

Cell phones

-

PDAs

-

GPS systems

-

Digital cameras

-

Multimedia / MP3 players

• LED flashlights

• Constant current power supplies

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