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
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
100mA
10µH
100mA
MIC2291xD5
5
MIC2291-15xML
1
1-Cell
Li Ion
3V to 4.2V
VIN
EN
SW
FB
GND
2
VIN
SW
OVP
FB
GND
95mV
0.22µF
1µF
4
3
0.22µF
ceramic
95mV
1-Cell
Li Ion
3V to 4.2V
1µF
EN
Thin SOT23 Flash LED Driver
PowerPAK is a trademark of Siliconix, Inc.
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
2mm x 2mm Flash LED Driver with Output OVP
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
Micrel, Inc.
MIC2291
Ordering Information
Part Number
MIC2291BD5
MIC2291YD5
MIC2291-15BML
MIC2291-15YML
MIC2291-34BML
MIC2291-34YML
Notes:
*
**
Under bar / Over bar symbol may not be to scale.
Over bar symbol located after Pin 1 identifier.
Marking*
SSAA
SSAA
STA
STA**
STC
STC**
Overvoltage
Protection
―
―
15
15
34
34
Junction
Temp. Range
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
Package
5-Pin Thin SOT23
5-Pin Thin SOT23
8-Pin 2mm x 2mm MLF
®
8-Pin 2mm x 2mm MLF
®
8-Pin 2mm x 2mm MLF
®
8-Pin 2mm x 2mm MLF
®
Lead Finish
Standard
Pb-Free
Standard
Pb-Free
Standard
Pb-Free
Pin Configuration
FB GND SW
1
2
3
OVP
VIN
EN
PGND
SW
FB
NC
1
2
3
4
8
7
6
4
EN
5
VIN
AGND
EP
5
5-Pin TSOT23 (D5)
®
8-Pin 2mm x 2mm MLF (ML)
Pin Description
Pin Number
TSOT23-5
1
2
3
6
Pin Number
2x2 MLF-8
7
SW
GND
FB
Switch node (Output): Internal power BIPOLAR collector.
Ground (Return): Ground.
Feedback (Input): Output voltage sense node. Connect the cathode
of the LED to this pin. Connect current set resistor from this pin to
ground.
Enable (Input): Logic high (≥1.5V) enables regulator. Logic low
(≤0.4V) shuts down regulator.
Supply (Input): Input Voltage.
Overvoltage protection (Input): Connect to the output to clamp the
maximum output voltage.
Analog ground. Internally connected to ground.
Power ground.
No connect (no internal connection to die).
Ground (Return): Exposed backside pad.
Pin Name
Pin Name
4
5
―
―
―
―
―
3
2
1
4
8
5
EP
EN
VIN
OVP
AGND
PGND
NC
GND
May 2007
2
M9999-051507
Micrel, Inc.
MIC2291
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) .......................................................12V
Switch Voltage (V
SW
)....................................... –0.3V to 34V
Enable Pin Voltage (V
EN
)................................... –0.3V to V
IN
FB Voltage (V
FB
)...............................................................6V
Switch Current (I
SW
) .........................................................2A
Storage Temperature (T
s
) .........................–65°C to +150°C
ESD Rating
(3)
.................................................................. 2kV
Operating Ratings
(2)
Supply Voltage (V
IN
).......................................... 2.5V to 10V
Junction Temperature (T
J
) ........................ –40°C to +125°C
Package Thermal Resistance
2x2 MLF-8 (θ
JA
) .................................................93°C/W
Thin SOT23-5 (θ
JA
)..........................................256°C/W
Electrical Characteristics
(4)
T
A
= 25°C, V
IN
= V
EN
= 3.6V; V
OUT
= 10V; I
OUT
= 40mA,
bold
values indicate –40°C< T
J
< +125°C, unless noted.
Symbol
V
IN
V
UVLO
I
VIN
I
SD
V
FB
I
FB
Parameter
Supply Voltage Range
Under Voltage Lockout
Quiescent Current
Shutdown Current
Feedback Voltage
Feedback Input Current
Line Regulation(7)
Load Regulation(7)
D
MAX
I
SW
V
SW
I
SW
V
EN
I
EN
f
SW
V
OVP
T
J
Notes:
1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating
the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, T
J(max)
, the
junction-to-ambient thermal resistance,
θ
JA
, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die
temperature, and the regulator will go into thermal shutdown.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model.
4. Specification for packaged product only.
5. I
SD
= I
VIN
.
6. See “Typical Characteristics” section for other V
EN
.
7. Guaranteed by design.
Condition
Min
2.5
1.8
Typ
2.1
2.8
0.1
Max
10
2.4
5
1
100
1
Units
V
V
mA
µA
mV
nA
%
%
%
A
mV
V
FB
> 200mV, (not switching)
V
EN
= 0V(5)
(±5%)
V
FB
= 95mV
3V
≤
V
IN
≤
5V
5mA
≤
I
OUT
≤
40mA
85
I
SW
= 1.0A
V
EN
= 0V, V
SW
= 10V
TURN ON
TURN OFF
V
EN
= 10V(6)
1.05
MIC2291BML- 15 only
MIC2291BML- 34 only
Hysteresis
13
30
1.5
90
95
–450
0.5
0.5
90
1.2
550
0.01
Maximum Duty Cycle
Switch Current Limit
Switch Saturation Voltage
Switch Leakage Current
Enable Threshold
Enable Pin Current
Oscillator Frequency
Overvoltage Protection
Overtemperature
Threshold Shutdown
5
0.4
µA
V
V
µA
MHz
V
V
°C
°C
20
1.2
14
32
150
10
40
1.35
16
34
May 2007
3
M9999-051507
分立器件
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