MIC2297_08 Datasheet, PDF (1/11 Pages) Micrel Semiconductor – 40V PWM Boost Regulator White LED Driver

MIC2297
40V PWM Boost Regulator
White LED Driver
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^® package. The MIC2297 has a
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
• 10-pin 2.5mm x 2.5mm MLF^® package
• –40^oC to +125^oC junction temperature range
Applications
• PDAs
• GPS systems
• Smart phones
• Mini PCs
• Digital cameras
• IP phones
• LED flashlights
___________________________________________________________________________________________________________
Typical Applications
6.8µH-22µH
6.8µH-22µH
1-Ce l l
Li I on
3V to 4.2V
1µF
1µF
VIN
SW
EN
OVP
MIC2297
BRT -42BM L
REF
FB
AGND PGND COMP
0.1µF
0.47µF
/50V ^{1-Ce ll}
Li I on
3V to 4.2V
10
1µF PWM
1µF
VIN
SW
EN
OVP
MIC2297
BRT -42BM L
REF
FB
AGND PGND COMP
0.1µF
0.47µF
/50V
10
10 Series LED Driver with Output OVP
10 Series LED Driver with PWM Brightness Control
MLF and MicroLeadFrame is a trademark of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
March 2008
M9999-032708