MIC2291
1.2A PWM Boost Regulator Photo Flash
LED Driver
PowerPAK is a trademark of Siliconix, Inc.
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
May 2007
1 M9999-051507
General Description
The MIC2291 is a 1.2MHz Pulse Width Modulation (PWM),
boost-switching regulator that is optimized for high-current,
white LED photo flash applications. With a guaranteed
switch current of 1.2A, the MIC2291 easily drives a string
of 3 white LEDs in series at 100mA, ensuring a high level
of brightness and eliminating several ballast resistors.
The MIC2291 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 contrast 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 MIC2291 is available with 2 levels of over-voltage
protection, 15V, and 34V. This allows designers to choose
the smallest possible external components with the
appropriate voltage ratings for their applications.
The MIC2291 is available in low-profile, Thin SOT23 5-pin
and 8-pin 2mm × 2mm MLF
®
package options. The
MIC2291 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
• 1.2A switch current
• 1.2MHz PWM operation
• 95mV feedback voltage
• Overvoltage protection (OVP)
– Options for 15V and 34V
• Stable with ceramic capacitors
• <1% line and load regulation
• 1µA shutdown current
• Over temperature protection
• UVLO
• Low-profile Thin SOT23-5 package option
• 2mm × 2mm MLF
®
package option
• –40°C to +125°C junction temperature range
Applications
• Photo Flash LED driver
• Cell phones
• PDAs
• GPS systems
• Digital cameras
• IP phones
• LED flashlights
Typical Application
10µH
0.22µF
ceramic
95mV
1-Cell
Li Ion
3V to 4.2V
1µF
2
3
1
4
5
MIC2291xD5
VIN
EN
SW
FB
GND
100mA
10µH
0.22µF
1µF1-Cell
Li Ion
3V to 4.2V
MIC2291-15xML
VIN
EN
SW
OVP
FB
GND 95mV
100mA
Thin SOT23 Flash LED Driver 2mm x 2mm Flash LED Driver with Output OVP
