January 2006

1

M9999-010306

MIC3287

Micrel, Inc.

MIC3287

Thin SOT-23 and 2mm x 2mm MFL™

General Description

The MIC3287 is a 1.2MHz pulse width modulated (PWM)

step-up switching regulator that is optimized for constant

current white LED driving applications. With a maximum

output voltage of 24V and a switch current of over 350mA,

the MIC3287 drives a string of up to 4 white LEDs in series,

ensuring uniform brightness and eliminating several ballast

resistors.

TheMIC3287implementsaconstantfrequency1.2MHzPWM

current-mode control scheme. The high frequency PWM op-

eration saves board space by reducing external component

sizes. The added benefit of the constant frequency PWM

control scheme as opposed to variable frequency control

schemes is much lower noise and input ripple injected back

to the battery source. To optimize efficiency, the feedback

voltage is set to only 250mV. The MIC3287 is also available

with a maximum 24V over-voltage protection.

The MIC3287 is available in low profile Thin SOT-23 5-pin

and Thin SOT-23 6-pin packages. The MIC3287 has a junc-

tion temperature range of –40°C to +125°C.

All support documentation can be found on Micrel’s web site

at: www.micrel.com.

Typical Application

10µH

0.22µF

250mV

1-Cell

Li Ion

1µF

2

3

1

4

5

MIC3287YD5

VIN

EN

SW

FB

GND

3-Series White LED Driver in Thin SOT-23-5

Features

• 2.8V to 5.5V Input Voltage

• 350mA Switch Current

• 1.2 MHz PWM Operation

• 250mV Feedback Voltage

• 24V Output Over-Voltage Protection (OVP) Option

• <1% Line and Load Regulation

• <1µA Shutdown Current

• Over-Temperature Protection

• Under-Voltage Lock Out (UVLO)

• Low Profile Thin SOT-23-5 Package Option

• Low Profile Thin SOT-23-6 Package Option

• 8-pin 2mm x 2mm MLF™ Package Option

• –40°C to +125°C Junction Temperature Range

Applications

• White LED Driver for Backlighting:

- Cell phones

- PDAs

- GPS systems

- Digital cameras

- MP3 players

- IP phones

• LED Flashlights

• Constant Current Power Supplies

Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.

10µH

0.22µF

1µF

1-Cell

Li Ion

MIC3287-24YD6

VIN

EN

SW

OVP

FB

GND

250mV

5

1

3

4

4

6

4-Series White LED Driver

with Output OVP in Thin SOT-23-6