Microchip MIC2291 Manual


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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 ash 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 benet 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-prole, 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-prole 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 ashlights
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
Micrel, Inc. MIC2291
May 2007
2 M9999-051507
Ordering Information
Part Number Marking* Overvoltage
Protection
Junction
Temp. Range
Package Lead Finish
MIC2291BD5 SSAA –40° to +125°C 5-Pin Thin SOT23 Standard
MIC2291YD5 SSAA –40° to +125°C 5-Pin Thin SOT23 Pb-Free
MIC2291-15BML STA 15 –40° to +125°C 8-Pin 2mm x 2mm MLF
®
Standard
MIC2291-15YML STA** 15 –40° to +125°C 8-Pin 2mm x 2mm MLF
®
Pb-Free
MIC2291-34BML STC 34 –40° to +125°C 8-Pin 2mm x 2mm MLF
®
Standard
MIC2291-34YML STC** 34 –40° to +125°C 8-Pin 2mm x 2mm MLF
®
Pb-Free
Notes:
* Under bar / Over bar symbol may not be to scale.
** Over bar symbol located after Pin 1 identifier.
Pin Configuration
FB GND
EN VIN
SW
31
5
2
4
OVP
VIN
EN
A
GND
PGND
SW
FB
NC
1
2
3
4
8
7
6
5
EP
5-Pin TSOT23 (D5) 8-Pin 2mm x 2mm MLF
®
(ML)
Pin Description
Pin Number
TSOT23-5
Pin Number
2x2 MLF-8
Pin Name Pin Name
1 7 SW Switch node (Output): Internal power BIPOLAR collector.
2 GND Ground (Return): Ground.
3 6 FB Feedback (Input): Output voltage sense node. Connect the cathode
of the LED to this pin. Connect current set resistor from this pin to
ground.
4 3 EN Enable (Input): Logic high (1.5V) enables regulator. Logic low
(0.4V) shuts down regulator.
5 2 VIN Supply (Input): Input Voltage.
1 OVP Overvoltage protection (Input): Connect to the output to clamp the
maximum output voltage.
4 AGND Analog ground. Internally connected to ground.
8 PGND Power ground.
5 NC No connect (no internal connection to die).
EP GND Ground (Return): Exposed backside pad.


Produkt Specifikationer

Mærke: Microchip
Kategori: Ikke kategoriseret
Model: MIC2291

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