MIC2291
Micrel
MIC2291
1.2A PWM Boost Regulator
Photo Flash LED Driver
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 appropri-
ate voltage ratings for their applications.
The MIC2291 is available in low-profile, Thin SOT23 5-lead
and 8-lead 2mm
脳
2mm MLF鈩?package options. The MIC2291
has a junction temperature range of 鈥?0擄C to +125擄C.
All support documentation can be found on Micrel鈥檚 web
site at www.micrel.com.
Features
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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)
鈥?Options for 15V and 34V
Stable with ceramic capacitors
<1% line and load regulation
1碌A(chǔ) shutdown current
Over temperature protection
UVLO
Low-profile Thin SOT23-5 package option
2mm
脳
2mm MLF鈩?package option
鈥?0擄C to +125擄C junction temperature range
Applications
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Photo Flash LED driver
Cell phones
PDAs
GPS systems
Digital cameras
IP phones
LED flashlights
Typical Application
10碌H
100mA
10碌H
100mA
MIC2291BD5
5
MIC2291-15BML
1
1-Cell
Li Ion
3V to 4.2V
VIN
EN
SW
FB
GND
2
VIN
0.22碌F
ceramic
95mV
0.95鈩?/div>
1-Cell
Li Ion
3V to 4.2V
1碌F
EN
SW
OVP
FB
GND
95mV
0.95鈩?/div>
0.22碌F
1碌F
4
3
Thin SOT23 Flash LED Driver
2mm
脳
2mm Flash LED Driver with Output OVP
MLF and
Micro
LeadFrame are trademarks of Amkor Technology, Inc.
PowerPAK is a trademark of Siliconix, Inc.
Micrel, Inc. 鈥?1849 Fortune Drive 鈥?San Jose, CA 95131 鈥?USA 鈥?tel + 1 (408) 944-0800 鈥?fax + 1 (408) 474-1000 鈥?http://www.micrel.com
August, 2004
1
M9999-081104
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