MIC3289
1.2MHz PWM White LED Driver with
Internal Schottky Diode and True 1-Wire
Digital Control
General Description
The MIC3289 is a PWM boost-switching regulator that is
optimized for constant-current white LED driver
applications. The MIC3289 features an internal Schottky
diode, allowing an efficient DC/DC solution that requires
only 4 external components.
The MIC3289 allows for a single wire simple digital
interface to control the dimming over 16 steps with a log
scale to give better resolution at the lower currents and to
better match the sensitivity of the human eye. The pre-
programming feature allows the user to select any one of
the 16 WLED current levels as the start-up brightness
level.
The feedback voltage of the MIC3289 is only 250mV,
allowing high efficiency while retaining excellent accuracy
for the white LED current.
The MIC3289 implements a constant frequency 1.2MHz
PWM control scheme. The high frequency PWM operation
saves board space by reducing external component sizes.
The 1.2MHz PWM scheme also reduces switching noise
and ripple to the input power source.
The 2.5V to 6.5V input voltage range of MIC3289 allows
direct operation from single cell Li Ion as well as 3- to 4-
cell NiCad/NiMH/Alkaline batteries.
Battery life is
preserved with a low 1µA shutdown current.
The MIC3289 is available in a low profile Thin SOT23 6-
®
lead package and a 2mm × 2mm MLF -8L package and
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
•
Single wire combines 16 level logarithmic brightness &
shutdown control
•
16V / 24V OVP options supports up to 4 & 6 WLEDs
•
Start-up in any one of 16 brightness levels
•
Internal Schottky diode
•
2.5V to 6.5V input voltage
•
1.2 MHz PWM operation
•
Over 500mA switch current
•
250mV reference voltage
• ±5%
LED current accuracy
•
<1µA shutdown current
•
Over temperature protection
•
UVLO
•
Thin SOT23-6L package option
®
•
2mm × 2mm leadless MLF -8L package option
o
o
•
–40 C to +125 C junction temperature range
Applications
•
White/Blue LED driver for backlighting
-
Cell phones
-
PDAs
-
GPS systems
-
Digital cameras
-
Multimedia / MP3 players
•
LED flashlights
•
Constant current power supplies
___________________________________________________________________________________________________________
MicroLead Frame and MLF are registered trademarks of Amkor Technologies.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 2007
M9999-061807
(408) 944-0800
Micrel, Inc.
MIC3289
Pin Description
Pin Number
SOT23-6
Pin Number
8-pin MLF
®
Pin Name
Pin Name
6
5
4
-
3
1
2
-
1
2
3
5
6
7
4,8
Pad
OUT
VIN
DC
N/C
FB
SW
GND
GND
Output and Over Voltage Protection (output)
Supply (Input): 2.5V to 6.5V for internal circuitry.
Single pin digital control. See diagrams.
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.
June 2007
3
M9999-061807
(408) 944-0800
Micrel, Inc.
MIC3289
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,
Note 3
..................................................... 2KV
Operating Ratings
(2)
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 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
o
V
IN
V
UVLO
I
VIN
I
SD
V
FB
I
FB
Supply Voltage Range
Under-voltage Lockout
Quiescent Current
Shutdown Current (DC pin
low )
Feedback Voltage
Feedback Input Current
Line Regulation
Load Regulation
V
FB
>500mV
V
DC
= 0V for > 2ms.
(+/-5%)
V
FB
= 250mV
2.5V
≤
V
IN
≤
4.5V
5mA
≤
I
OUT
≤
20mA
2.5
1.8
2.1
1.4
0.01
237
250
450
0.5
0.5
85
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
35
1
1.2
500
1.1
90
750
6.5
2.4
5
1
263
V
V
mA
µA
mV
nA
%
%
%
D
MAX
I
SW
V
DC
Maximum Duty Cycle
Switch Current Limit
DC pin thresholds
DC Pin Hysteresis
1200
0.4
mA
V
mV
20
5
10
I
DC
t
shutdown
t
MODE_UP
t
MODE_DO
WN
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
µA
µs
160
500
µs
µs
µs
t
start_up
t
prog_low
t
prog
_
high
t
delay
T
prog_setup
f
SW
32
32
µs
µs
µs
50
1.35
µs
MHz
June 2007
4
M9999-061807
(408) 944-0800
Micrel, Inc.
Symbol
Parameter
Condition
Min
Typ
Max
MIC3289
Units
V
D
I
RD
V
OVP
Schottky Forward Drop
Schottky Leakage Current
Over Voltage Protection
Over-Temperature
Threshold Shutdown
I
D
= 150mA
V
R
= 30V
3289- 16 only (nominal voltage)
3289- 24 only (nominal voltage)
13
21
0.8
14
22.5
150
1
4
16
24
V
µA
V
V
°C
Tj
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, T
A
. The maximum allowable power dissipation will result in excessive die
temperature, and the regulator will go into thermal shutdown.
This device is not guaranteed to operate beyond its specified operating rating.
IC devices are inherently ESD sensitive. Handling precautions required.
Specification for packaged product only.
2.
3.
4.
June 2007
5
M9999-061807
(408) 944-0800
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