MIC3291
1.2MHz PWM White LED Driver
with Internal Schottky Diode and
Single-Wire Linear Brightness
Control
General Description
Features
The MIC3291 is a PWM switching boost regulator that is
•
Single wire combines 16 level linear brightness and
optimized for constant current white LED (WLED) driver
shutdown control
applications. The MIC3291 features an internal Schottky
•
18V / 25V OVP options supports up to four and six
diode, allowing an efficient DC/DC solution that requires
WLEDs
only four external components.
•
Startup in any one of 16 brightness levels
The MIC3291 allows for a single-wire simple digital
•
Internal Schottky diode
interface to control the dimming over 16 steps with a linear
•
2.5V to 6.5V input voltage
scale. The preprogramming feature allows the user to
•
1.2MHz PWM operation
select any one of the 16 WLED current levels as the start
up brightness level.
•
Over 500mA switch current
The feedback voltage of the MIC3291 is only 250mV,
•
250mV reference voltage
allowing high efficiency while retaining excellent accuracy
• ±5%
LED current accuracy
for the WLED current.
•
<1µA shutdown current
The MIC3291 implements a constant frequency 1.2MHz
•
UVLO and over-temperature protection
PWM control scheme. The high frequency PWM operation
•
Thin SOT23-6L package option
saves board space by reducing external component sizes.
The 1.2MHz PWM scheme also reduces switching noise
•
2mm × 2mm leadless MLF
®
package option
and ripple to the input power source.
•
–40
o
C to +125
o
C junction temperature range
The 2.5V to 6.5V input voltage range of the MIC3291
allows direct operation from single cell Li-Ion as well as 3
Applications
to 4 cell NiCad/NiMH/Alkaline batteries. Battery life is
preserved with a low 1µA shutdown current.
•
Mobile handsets
The MIC3291 is available in a low profile Thin SOT23 6-
•
LCD handset backlighting
®
pin and 2mm × 2mm MLF 8-pin packages with a junction
•
Digital cameras
temperature range of –40°C to +125°C.
•
Portable media players/MP3 players
Data sheets and support documentation can be found on
•
Portable applications
Micrel’s web site at:
www.micrel.com.
___________________________________________________________________________________________________________
Typical Application
White LED Driver with OVP and Digital Control
MLF and
MicroLead
Frame are registered trademarks of Amkor Technologies, 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
September 2010
M9999-092810
(408) 944-0800
Micrel, Inc.
MIC3291
Ordering Information
Part Number
1
MIC3291-18YD6
MIC3291-25YD6
MIC3291-18YML
MIC3291-25YML
Notes:
1.
2.
3.
4.
Other options available. Contact Micrel Marketing for details.
MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
MLF
®
®
Marking Code
4
W18F
W25F
WAF
Output Voltage
Adjustable
Adjustable
Adjustable
Adjustable
Over-Voltage
Protection
18V
25V
18V
25V
Junction
Temperature Range
−40°C
to
+125°C
−40°C
to
+125°C
−40°C
to
+125°C
−40°C
to
+125°C
Package
2,3
TSOT23-6
TSOT23-6
2mm
×
2mm MLF
®
2mm
×
2mm MLF
®
WBF
●
= Pin 1 identifier.
Overbar ( ¯ )and Underbar symbols ( _ ) may not be to scale.
Pin Configuration
2mm × 2mm 8-Pin MLF
®
(ML)
(Top View)
TSOT23-6 (D6)
(Top View)
Pin Description
Pin Number
8-pin MLF
1
2
3
4
5
6
7
8
Pad
®
Pin Number
SOT23-6
6
5
4
−
−
3
1
2
−
Pin Name
OUT
VIN
DC
GND
NC
FB
SW
GND
GND
Pin Name
Output and over-voltage protection (output)
Supply (Input): 2.5V to 6.5V for internal circuitry.
Single pin digital control. See diagrams.
Ground (Return): Ground.
No connect (no internal connection to die)
Feedback (Input): Output voltage sense node. Connect the cathode of the LED
to this pin.
Switch Node (Input): Internal power BIPOLAR collector.
Ground (Return): Ground.
Ground (Return): Backside pad.
September 2010
2
M9999-092810
(408) 944-0800
Micrel, Inc.
MIC3291
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) .................................................... 7.5V
Switch Voltage (V
SW
) ..................................... –0.3V to 27V
Digital Control Voltage (V
DC
) ..............................–0.3 to V
IN
FB Voltage (V
FB
)............................................................. 6V
Switch Current (I
SW
)........................................................ 2A
Ambient Storage Temperature (T
S
)......... –65°C to +150°C
ESD Rating
(2)
................................................................2KV
Operating Ratings
(3)
Supply Voltage (V
IN
) …………………..…… ......2.5V to 6.5V
Output Voltage (V
OUT
) …………….… ............... (V
IN
to V
OVP
)
Junction Temperature Range (T
J
) …… ....
−40°C
to +125°C
Package Thermal Impedance
θ
JA
2mm × 2mm MLF
®
-8L ................................. 93°C/W
θ
JA
TSOT23-6 .................................................. 235°C/W
Electrical Characteristics
(4)
T
A
=
+25
o
C, V
IN
= 3.6V, V
OUT
= 10V, I
OUT
= 20mA, unless otherwise noted.
Bold
values indicate
−40°C ≤
T
J
≤ +125°C.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
V
IN
V
UVLO
I
VIN
I
SD
V
FB
I
FB
D
MAX
I
SW
V
DC
I
DC
t
shutdown
t
MODE_UP
t
MODE_DOWN
t
start_up
t
prog_low
t
prog
_
high
t
delay
T
prog_setup
f
SW
Supply Voltage Range
Under-Voltage Lockout
Quiescent Current
Shutdown Current (DC Pin Low )
Feedback Voltage
Feedback Input Current
Line Regulation
Load Regulation
Maximum Duty Cycle
Switch Current Limit
DC Pin Thresholds
DC Pin Current
Shutdown Pulse Width
Count UP Mode Pulse Width
Count Down Mode Pulse Width
Turn-On Delay Time
Programming Pulse Width Low
Programming Pulse Width High
Minimum Delay for Mode Change
First Pulse Window for
Preprogramming
Oscillator Frequency
2.5
1.8
V
FB
>500mV
V
DC
= 0V for > 2ms.
(±5%)
V
FB
= 250mV
2.5V
≤
V
IN
≤
4.5V
5mA
≤
I
OUT
≤
20mA
V
IN
= 3.6V
High
Low
V
DC
= 3.6V
V
IN
= 2.8V to 5.5V
V
DC
= Low
V
IN
= 2.8V to 5.5V
V
DC
= Low
V
IN
= 2.8V to 5.5V
V
DC
= Low
V
IN
= 2.8V to 5.5V
V
IN
= 2.8V to 5.5V
V
IN
= 2.8V to 5.5V
V
IN
= 2.8V to 5.5V
V
DC
= High
V
IN
= 2.8V to 5.5V
1260
100
420
140
1
1
140
86
500
1.1
237
2.1
2
0.01
250
450
0.5
0.5
90
750
6.5
2.4
4
1
263
V
V
mA
μA
mV
nA
%
%
mA
V
μA
µs
1200
0.4
5
10
160
500
µs
µs
µs
µs
µs
µs
32
32
35
1
1.2
50
1.35
µs
MHz
September 2010
3
M9999-092810
(408) 944-0800
Micrel, Inc.
MIC3291
Electrical Characteristics
(4)
(Continued)
T
A
=
+25
o
C, V
IN
= 3.6V, V
OUT
= 10V, I
OUT
= 20mA, unless otherwise noted.
Bold
values indicate
−40°C ≤
T
J
≤ +125°C.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
V
D
I
RD
V
OVP
Tj
Notes:
1.
Schottky Forward Drop
Schottky Leakage Current
Over-Voltage Protection
Over-Temperature
Threshold Shutdown
I
D
= 150mA
V
R
= 30V
3291- 18 only (nominal voltage)
3291- 25 only (nominal voltage)
15
22.1
0.8
16.5
23.5
150
1
4
18
25
V
μA
V
°C
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.
IC devices are inherently ESD sensitive. Handling precautions required. Human body model, 1.5kΩ in series with 100pF.
This device is not guaranteed to operate beyond its specified operating rating.
Specification for packaged product only.
2.
3.
4.
September 2010
4
M9999-092810
(408) 944-0800
Micrel, Inc.
MIC3291
Typical Characteristics
275
FEEDBACK VOLTAGE (mV)
250
225
175
150
125
100
75
50
25
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
BRIGHTNESS LEVEL (0-15)
EFFICIENCY (%)
200
Feedback Voltage
vs. Brightness Level
100
90
80
60
50
40
30
20
10
0
0
70
6 Series White LED
Efficiency
V
IN
= 2.8V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
3 Series White LED
Efficiency
V
IN
= 2.8V
V
IN
= 4.2V
V
IN
= 3.6V
L = 10µH
C
OUT
= 0.27µF
5
10
15
20
25
V
IN
= 3.6V
V
IN
= 4.2V
L = 10µH
C
OUT
= 0.27µF
0
5
10
15
20
25
WHITE LED CURRENT (mA)
WHITE LED CURRENT (mA)
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
6 Series White LED
Efficiency
V
IN
= 4.2V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
3 Series White LED
Efficiency
FEEDBACK VOLTAGE (mV)
260
258
256
254
252
250
248
246
244
242
240
25
2.5
Feedback Voltage
vs. Input Voltage
V
IN
= 3.6V
V
IN
= 2.8V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 2.8V
L = 22µH
C
OUT
= 0.27µF
5
10
15
20
25
L = 22µH
C
OUT
= 0.27µF
0
5
10
15
20
3
3.5
4
4.5
5
5.5
6
WHITE LED CURRENT (mA)
WHITE LED CURRENT (mA)
INPUT VOLTAGE (V)
1000
FEEDBACK VOLTAGE (mV)
900
Peak Switch Current
vs. Input Voltage
INPUT CURRENT (mA)
350
300
250
200
150
100
50
0
Input Current
vs. Input Voltage
L=10µH
CURRENT LIMIT (A)
1
0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.6
Current Limit
vs. Input Voltage
800
700
600
500
400
300
200
2.5
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
6 LEDs
3 LEDs
2.5
3
3.5
4
4.5
5
5.5
6
2.6 3.1 3.6 4.1 4.6 5.1 5.6 6.1 6.6
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
September 2010
5
M9999-092810
(408) 944-0800
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