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
•
Single wire combines 16 level linear brightness and
optimized for constant current white LED (WLED) driver
shutdown control
applications. The MIC3291 features an internal Schottky
•
18V / 25V OVP options supports up to four and six
diode, allowing an efficient DC/DC solution that requires
WLEDs
only four external components.
•
Startup in any one of 16 brightness levels
The MIC3291 allows for a single-wire simple digital
•
Internal Schottky diode
interface to control the dimming over 16 steps with a linear
•
2.5V to 6.5V input voltage
scale. The preprogramming feature allows the user to
•
1.2MHz PWM operation
select any one of the 16 WLED current levels as the start
up brightness level.
•
Over 500mA switch current
The feedback voltage of the MIC3291 is only 250mV,
•
250mV reference voltage
allowing high efficiency while retaining excellent accuracy
• ±5%
LED current accuracy
for the WLED current.
•
<1µA shutdown current
The MIC3291 implements a constant frequency 1.2MHz
•
UVLO and over-temperature protection
PWM control scheme. The high frequency PWM operation
•
Thin SOT23-6L package option
saves board space by reducing external component sizes.
The 1.2MHz PWM scheme also reduces switching noise
•
2mm × 2mm leadless MLF
®
package option
and ripple to the input power source.
•
–40
o
C to +125
o
C junction temperature range
The 2.5V to 6.5V input voltage range of the MIC3291
allows direct operation from single cell Li-Ion as well as 3
Applications
to 4 cell NiCad/NiMH/Alkaline batteries. Battery life is
preserved with a low 1µA shutdown current.
•
Mobile handsets
The MIC3291 is available in a low profile Thin SOT23 6-
•
LCD handset backlighting
®
pin and 2mm × 2mm MLF 8-pin packages with a junction
•
Digital cameras
temperature range of –40°C to +125°C.
•
Portable media players/MP3 players
Data sheets and support documentation can be found on
•
Portable applications
Micrel’s web site at:
___________________________________________________________________________________________________________
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 +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
September 2010
M9999-092810
(408) 944-0800