MIC2289

White LED Driver Internal Schottky

Diode and OVP

MLF and MicroLeadFrame are registered trademarks of Amkor Technology, 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

July 2007

M9999-071007

General Description

The MIC2289 is a PWM (pulse width modulated), boost-

switching regulator that is optimized for constant-current

white LED driver applications. The MIC2289 features an

internal Schottky diode and three levels of output

overvoltage protection providing a small size and efficient

DC/DC

solution

that

requires

only

four

external

components.

To optimize efficiency, the feedback voltage is set to only

95mV. This reduces power dissipation in the current set

resistor and allows the lowest total output voltage, hence

minimal current draw from the battery.

The MIC2289 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

in caparison to variable frequency is much lower noise and

input ripple injected to the input power source.

The MIC2289 clamps the output voltage in case of open

LED conditions, protecting itself and the output capacitor.

The MIC2289 is available with three output OVP options of

15V, 24V, and 34V. The different OVP options allows the

use of the smallest possible output capacitor with the

appropriate voltage rating for a given application.

The MIC2289 is available in low profile 6-pin Thin SOT-23

and 8-pin 2mm × 2mm MLF

MIC2289 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

• 2.5V to 10V input voltage

• Output voltage up to 34V

• Internal Schottky diode

• 15V, 24V, 34V output OVP options

• 1.2 MHz PWM operation

• Over 500mA switch current

• 95mV feedback voltage

• <1% line and load regulation

• <1µA shutdown current

• Overtemperature protection

• UVLO

• –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

Typical Application

10µH

0.22µF/16V

95mV

1-Cell

Li Ion

1µF

MIC2289-15BML

VIN

EN

SW

FB

OUT

GND

3-Series White LED Driver

70

72

74

76

78

80

82

0

5

10

15

20

25

I

3-Series LED Efficiency

V