MIC2297

40V PWM Boost Regulator

White LED Driver

MLF and MicroLeadFrame is a trademark of Amkor Technology, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (

March 2008

M9999-032708

General Description

The MIC2297 is a 600KHz PWM boost-switching regulator

that is optimized for driving 6-10 series white LEDs. With

its internal 40V switch and a guaranteed switch current of

1.2A, the MIC2297 easily drives a string of 10 white LEDs

in series at 20mA, ensuring a high level of brightness and

eliminating several ballast resistors.

The MIC2297 implements constant frequency 600KHz

PWM control. The high frequency PWM operation saves

board space by reducing external component sizes. The

added benefit of the constant frequency PWM operation is

much lower noise and input ripple injected back to the

battery source than with variable frequency topologies.

To optimize efficiency, the feedback voltage is set to

200mV. This reduced voltage reduces the power

dissipation in the current set resistor, and allows the lowest

total output voltage, hence minimal current draw from the

battery.

The MIC2297 is available with output over-voltage

protection that protects the IC and external components in

case of open LED conditions.

The MIC2297 is available in low profile small size 10-pin

2.5mm x 2.5mm MLF

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

Features

• 2.5V to 10V input voltage range

• Output voltage up to 40V

• 1.2A switch current

• 600KHz PWM operation

• Trimmed 200mV feedback voltage

• Output over voltage protection (fixed or adjustable)

• PWM Brightness Control

• DAC Brightness Control

• <1% line regulation

• 1µA shutdown current

• Over temperature protection

• UVLO

Applications

• PDAs

• GPS systems

• Smart phones

• Mini PCs

• Digital cameras

• IP phones

• LED flashlights

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Typical Applications

VIN

EN

SW

FB

MIC2297

-42BM L

0.47µF

/50V

6.8µH-22µH

10

OVP

PGND

1µF

1-Cell

Li I on

3V to 4.2V

BRT

REF

AGND

COMP

1µF

PWM

VIN

EN

SW

FB

MIC2297

-42BM L

0.47µF

/50V

6.8µH-22µH

10

OVP

PGND

1µF

1-Ce ll

Li I on

3V to 4.2V

BRT

REF

AGND

COMP

0.1µF

1µF

0.1µF

10 Series LED Driver with Output OVP

10 Series LED Driver with PWM Brightness Control