MIC2298
3.5A Minimum, 1MHz Boost High
Brightness White LED Driver
General Description
The MIC2298 is a high power boost-switching regulator
that is optimized for constant-current control. The MIC2298
is capable of driving up to 2 series 1A white LED for
photoflash, flashlight and other applications. The feedback
voltage is only 200mV, minimizing ballast power dissipa-
tion in constant-current control applications for improved
operating efficiency.
The MIC2298 has a brightness pin that allows for a
programmable torch mode as well full flash with a single
pin when driving high current LEDs.
The MIC2298 implements a constant frequency 1MHz
PWM control scheme to make the smallest possible
design.
The 2.5V to 10V input voltage range of MIC2298 allows
direct operation from 1- and 2-cell Li Ion as well as 3- to 6-
cell NiCad/NiMH/Alkaline battery sources. Maximum
battery life is assured with a low 1µA shutdown current.
The MIC2298 is available in a low profile 12-pin 3x3 MLF
®
package.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
•
3.5A minimum switch current delivers at least 7W of
output power over-temperature
•
200mV
±10%
feedback voltage
•
2.5V to 10V input voltage
•
Output voltage up to 30V (max)
•
12-pin 3mm x 3mm leadless MLF
®
package
•
Available output over-voltage protection (OVP)
•
1MHz operation
•
Programmable output current
•
<1% line regulation
•
1µA shutdown current
•
Over temperature protection
•
Externally programmable soft-start
•
Under-voltage lockout (UVLO)
•
–40
°
C to +125
°
C junction temperature range
Applications
•
•
•
•
Cell phones
PDAs
Digital cameras
White LED flashlights
___________________________________________________________________________________________________________
Typical Application
Figure 1. High Power White LED Driver
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
October 2007
M9999-101707-B
Micrel, Inc.
MIC2298
Ordering Information
Part Number
MIC2298-15YML
®
OVP
15V
Frequency
1MHz
Junction Temp. Range
–40° to +125°C
Package
12-Pin 3x3 MLF
®
Lead Finish
Pb-Free
Note:
MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Pin Configuration
BRT
SS/DIM
FB
AGND
PGND
PGND
1
2
3
4
5
6
EP
12 COMP
11 EN
10 VIN
9
8
7
OVP
SW
SW
12-Pin 3mm x 3mm MLF (ML)
(Top View)
Pin Description
Pin Number
1
Pin Name
BRT
Pin Function
BRT (input): Apply a voltage greater than or equal to 1V to achieve full
brightness current as determined by the ballast resistor. A 10µA current source
sets the voltage on the resistor. Hence a 50K resistor would yield 0.5V which
causes a reduction in LED current to 50% of full brightness. Grounding the BRT
reduces the current further to 20% of full brightness. This pin may also be driven
by a PWM signal for the same effect.
Soft start/dimming (input) 40k
Ω
source. Connect a capacitor to GND for soft-
start. Clamp the pin to a known voltage to control the internal reference voltage
and hence the output current. This can also be done with a resistor to GND
Feedback (Input): Output voltage sense node. Connect the cathode of the LED
to this pin.
Analog Ground
Power Ground
Switch Node: Internal power BIPOLAR collector.
Over-Voltage Protection (OVP): Connect to the output voltage to clamp the
maximum output voltage. A resistor divider from this pin to ground could be
used to raise the OVP level beyond 15V (max)
Supply (Input): 2.5V to 10V for internal circuitry.
Enable (Input): Applying 1.5V or greater enables the regulator. Applying a
voltage of 0.4V or less disables the MIC2298.
Compensation pin (input): Add external R and C to GND to stabilize the
converter.
Ground (Return): Backside exposed pad.
2
SS/DIM
3
4
5,6
7,8
9
FB
AGND
PGND
SW
OVP
10
11
12
Pad
VIN
EN
COMP
EP
October 2007
2
M9999-101707-B
Micrel, Inc.
MIC2298
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) .......................................................12V
Switch Voltage (V
SW
)....................................... –0.3V to 34V
BRT Voltage (V
BRT
) ........................................... –0.3V to 6V
SS/DIM Voltage (V
SS
)........................................ –0.3V to 6V
Enable Voltage (V
EN
)....................................... –0.3V to 12V
FB Voltage (V
FB
)...............................................................6V
Switch Current (I
SW
) .........................................................6A
Ambient Storage Temperature (T
s
) ...........–65°C to +150°C
ESD Rating
(3)
.................................................................. 2kV
Operating Ratings
(2)
Supply Voltage (V
IN
).......................................... 2.5V to 10V
BRT Voltage (V
BRT
) ........................................... 0V to 0.6V
IN
Enable Voltage (V
EN
).............................................. 0V to V
IN
Output Voltage (V
OUT
) ................................... V
IN
+ 1 to V
OVP
Junction Temperature (T
J
) ........................ –40°C to +125°C
Package Thermal Impedance
3x3 MLF-12 (θ
JA
) ...............................................60°C/W
Electrical Characteristics
(4)
T
A
= 25°C; V
IN
= V
EN
= 3.6V; V
OUT
= 7V; I
OUT
= 1A, unless otherwise noted.
Bold
values indicate –40°C< T
J
< +125°C.
Symbol
V
IN
V
UVLO
V
OVP
I
VIN
I
SD
V
FB
I
FB
Parameter
Supply Voltage Range
Under-Voltage Lockout
Over-Voltage Protection
Quiescent Current
Shutdown Current
Feedback Voltage
Feedback Input Current
Line Regulation
Condition
Min
2.5
1.8
12
Typ
2.1
13.5
15
0.1
Max
10
2.4
15
23
1
216
220
Units
V
V
V
mA
µA
mV
nA
%
V
FB
>200mV, Not Switching
V
EN
= 0V (Note 5)
(+/-8%)
(+/-10%) (Over Temp)
V
FB
= 200mV
2.5V
≤
V
IN
≤
4.5V
R
BRT
= GND
R
BRT
= 50K
184
180
200
-650
0.5
I
LED
D
MAX
I
SW
V
SW
I
SW
V
EN
I
EN
f
SW
I
SS
T
J
Notes:
BRT accuracy (Note 6)
Maximum Duty Cycle
Switch Current Limit
Switch Saturation Voltage
Switch Leakage Current
Enable Threshold
Enable Pin Current
Oscillator Frequency
Soft start / DIM current
Over-Temperature Threshold
Shutdown
17
45
85
20
50
90
4.75
350
0.01
23
55
%
%
V
IN
= 3V
V
IN
= 3.6V, I
SW
= 3.5 A
V
EN
= 0V, V
SW
= 15V
TURN ON
TURN OFF
V
EN
= 10V
3.5
8
500
A
mV
µA
V
µA
MHz
µA
10
0.4
1.5
20
0.8
1
5
150
10
40
1.2
DIM = 0V
Hysteresis
°
C
°
C
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, T
A
. 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.
4. Specification for packaged product only.
5. I
SD
= I
VIN
6. As percentage of full brightness where V
IN
= V
BRT
= 3.6V (100% brightness)
October 2007
3
M9999-101707-B
Micrel, Inc.
MIC2298
Typical Characteristics
20
16
12
8
4
0
0
UVLO (V)
Input Current
vs. Input Voltage
2.4
2.3
UVLO vs.
Temperature
1.2
Switching Frequency
vs. Input Voltage
1.1
2.2
2.1
2.0
0.9
1.0
1.9
2
4
6
8
10
INPUT VOLTAGE (V)
12
1.8
-40 -20 0 20 40 60
TEMPERATURE (°C)
80
0.8
2
T
A
= 25°C
3
4 5 6 7 8 9 10 11
INPUT VOLTAGE (V)
1.2
Switching Frequency
vs. Temperature
0.210
LED Current vs.
Input Voltage
(BRT GND)
1.00
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
LED Current vs.
Input Voltage
(BRT Open)
1.1
0.205
1.0
0.200
0.9
V
IN
= 5V
0.195
R
SENSE
T
CASE
= 25°C
0.8
-40 -20 0 20 40 60 80
TEMPERATURE (°C)
0.190
2.5 3 3.5 4 4.5 5 5.5 6 6.5
INPUT VOLTAGE (V)
R
SENSE
0.91
T
CASE
= 25°C
0.90
2.5 3 3.5 4 4.5 5 5.5 6 6.5
INPUT VOLTAGE (V)
1100
1000
900
800
700
600
500
400
300
200
100
0
0
LED Current
vs. DIM Voltage
95
90
85
80
75
70
65
Efficiency vs.
Input Voltage
(BRT Open)
95
90
85
80
75
70
Efficiency vs.
Input Voltage
(BRT GND)
40
80 120 160 200
DIM VOLTAGE (mV)
60
2.5 3 3.5 4 4.5 5 5.5 6 6.5
INPUT VOLTAGE (V)
R
SENSE
65
R
SENSE
60
2.5 3 3.5 4 4.5 5 5.5 6 6.5
INPUT VOLTAGE (V)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
Max DC LED Current
vs. Output Voltage
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
Max DC LED Current
vs. Output Voltage
25°C
50°C
500
450
400
350
300
250
200
150
100
Bipolar Saturation Voltage
vs. Switch Current
25°C
50°C
3.0V
3.6V
V
IN
= 3.0V
2
4
6
8 10 12 14
OUTPUT VOLTAGE (V)
V
IN
= 3.6V
2
4
6
8 10 12 14
OUTPUT VOLTAGE (V)
50
T
A
= 25°C
0
0 0.5 1 1.5 2 2.5 3 3.5 4
SWITCH CURRENT (A)
October 2007
4
M9999-101707-B
Micrel, Inc.
MIC2298
Functional Characteristics
October 2007
5
M9999-101707-B
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