MIC3291 Datasheet, PDF (1/17 Pages) Micrel Semiconductor – 1.2MHz PWM White LED Driver with Internal Schottky Diode and Single-Wire Linear Brightness Control

MIC3291
1.2MHz PWM White LED Driver
with Internal Schottky Diode and
Single-Wire Linear Brightness
Control
General Description
Features
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^® 8-pin packages with 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.
• 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
• 2mm × 2mm leadless MLF^® package option
• –40^oC to +125^oC junction temperature range
Applications
• Mobile handsets
• LCD handset backlighting
• Digital cameras
• Portable media players/MP3 players
• Portable applications
___________________________________________________________________________________________________________
Typical Application
White LED Driver with OVP and Digital Control
MLF and MicroLead Frame are registered trademarks of Amkor Technologies, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
September 2010
M9999-092810
[phone]