August 2004

1

M0510-081104

MIC2287

Micrel

MIC2287

2mm

××××× 2mm MLF™ and Thin SOT-23

General Description

The MIC2287 is a 1.2MHz pulse width modulated (PWM),

boost-switching regulator that is optimized for constant-

current, white LED driver applications. With a maximum

output voltage of 34V and a switch current of over 500mA, the

MIC2287 easily drives a string of up to 8 white LEDs in series,

ensuring uniform brightness and eliminating several ballast

resistors.

The MIC2287 implements a constant frequency, 1.2MHz

PWM control scheme. The high frequency PWM operation

saves board space by reducing external component sizes.

The added benefit of the constant frequency PWM scheme

as opposed to variable frequency topologies is much lower

noise and input ripple injected back to the battery source.

To optimize efficiency, the feedback voltage is set to only

95mV. This reduces the power dissipation in the current set

resistor and allows the lowest total output voltage, hence

minimal current draw from the battery.

The MIC2287 is available with 3 levels of overvoltage protec-

tion, 15V, 24V, and 34V. This allows designers to choose the

smallest possible external components with the appropriate

voltage ratings for their applications.

The MIC2287 is available in low profile Thin SOT-23 5-lead

and an 8-lead 2mm

× 2mm MLF™ package options. The

MIC2287 has a junction 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

10

µH

0.22

µF

6.3

Ω

95mV

1-Cell

Li Ion

1

µF

2

3

1

4

5

MIC2287BD5

VIN

EN

SW

FB

GND

CMDSH-3

3-Series White LED Driver in Thin SOT-23

Features

• 2.5V to 10V input voltage

• Output voltage up to 34V

• Over 500mA switch current

• 1.2 MHz PWM operation

• 95mV feedback voltage

• Output Overvoltage Protection (OVP)

• Options for 15V, 24V, and 34V OVP

• <1% line and load regulation

• <1

µA shutdown current

• Over-temperature protection

• UVLO

• Low profile Thin SOT-23-5 package option

• 8-lead 2mm

× 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

• Photo flash LED driver

• LED flashlights

• Constant current power supplies

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

MLF and

10

µH

0.22

µF

1

µF

1-Cell

Li Ion

6.3

Ω

MIC2287-34BML

VIN

EN

SW

OVP

FB

GND

95mV

CMDSH-3

6-Series White LED Driver

with Output OVP in 2mm

××××× 2mm MLF™-8