MIC2289
Micrel
MIC2289
2mm
×
2mm White LED Driver
with Internal Schottky Diode and OVP
General Description
The MIC2289 is a PWM (pulse width modulated), boost-
switching regulator that is optimized for constant-current
white LED driver applications. The MIC2289 features an
internal Schottky diode and three levels of output overvoltage
protection providing a small size and efficient DC/DC solution
that requires only four external components.
To optimize efficiency, the feedback voltage is set to only
95mV. This reduces power dissipation in the current set
resistor and allows the lowest total output voltage, hence
minimal current draw from the battery.
The MIC2289 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
caparison to varible frequency is much lower noise and input
ripple injected to the input power source.
The MIC2289 clamps the output voltage in case of open LED
conditions, protecting itself and the output capacitor. The
MIC2289 is available with three output OVP options of 15V,
24V, and 34V. The different OVP options allows the use of
the smallest possible output capacitor with the appropriate
voltage rating for a given application.
The MIC2289 is available in a 2mm
×
2mm 8-pin MLF™
package and has a junction temperature range of –40°C to
+125°C.
All 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
Internal Schottky diode
15V, 24V, 34V output OVP options
1.2 MHz PWM operation
Over 500mA switch current
95mV feedback voltage
<1% line and load regulation
<1mA shutdown current
Overtemperature protection
UVLO
2mm
×
2mm 8-pin MLF™ package
–40
°
C to +125
°
C junction temperature range
Applications
• White LED driver for backlighting
Cell phones
PDAs
GPS systems
Digital cameras
MP3 players
IP phones
• LED flashlights
• Constant current power supplies
Typical Application
3-Series LED Efficiency
10µH
82
80
EFFICIENCY (%)
MIC2289-15BML
1-Cell
Li Ion
VIN
1µF
OUT
EN
GND
6.3Ω
FB
95mV
SW
0.22µF/16V
78
76
74
72
70
0
V
IN
=3.6V
5
10
15
I
OUT
(mA)
20
25
3-Series White LED Driver
Micro
LeadFrame and MLF are trademarks of Amkor Technology, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
August, 2004
1
M9999-081104
MIC2289
Micrel
Ordering Information
Part Number
MIC2289-15BML
MIC2289-15YML
MIC2289-24BML
MIC2289-24YML
MIC2289-34BML
MIC2289-34YML
Marking
Code
SNA
SNA
SNB
SNB
SNC
SNC
Overvoltage
Protection
15V
15V
24V
24V
34V
34V
Junction
Temp. Range
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
Package
2mm
×
2mm MLF™-8
2mm
×
2mm MLF™-8
2mm
×
2mm MLF™-8
2mm
×
2mm MLF™-8
2mm
×
2mm MLF™-8
2mm
×
2mm MLF™-8
Lead Finish
Standard
Lead Free
Standard
Lead Free
Standard
Lead Free
Pin Configuration
OUT
VIN
EN
AGND
1
2
3
4
8
7
6
PGND
SW
FB
NC
EP
5
MLF™-8 (BML)
(Top View)
Fused Lead Frame
Pin Description
Pin Number
1
2
3
5
6
7
4,8
EP
Pin Name
OUT
VIN
EN
NC
FB
SW
GND
GND
Pin Function
Output Pin and Overvoltage Protection (Output): Connect to the output
capacitor and LEDs
Supply (Input): Input voltage.
Enable (Input): Logic high enables regulator, logic low shuts down regulator.
No connect (no internal connection to die).
Feedback (Input): Output voltage sense node. Connect the cathode of the
LED to this pin. A resistor from this pin to ground sets the LED current.
Switch Node (Input): Internal power transistor collector.
Ground (Return): Ground.
Ground (Return): Backside pad.
M9999-081104
2
August, 2004
MIC2289
Micrel
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) ..................................................... 12V
Switch Voltage (V
SW
) ..................................... –0.3V to 34V
Enable Pin Voltage (V
EN
) ................................... –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
Schottky Reverse Voltage (V
DA
) ................................... 34V
ESD Rating
(3)
................................................................ 2kV
Operating Ratings
(2)
Supply Voltage (V
IN
) ........................................ 2.5V to 10V
Output Voltage (V
OUT
) ..................................... V
IN
to V
OVP
Junction Temperature Range (T
J
) ........... –40°C to +125°C
Package Thermal Impedance
2mm
×
2mmMLF™-8 (θ
JA
) .................................. 93°C/W
Electrical Characteristics
(4)
T
A
= 25°C, V
IN
= V
EN
= 3.6V, V
OUT
= 10V, I
OUT
= 20mA, unless otherwise noted.
Bold
values indicate –40°C
≤
T
J
±125°C.
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
Load Regulation
D
MAX
I
SW
V
SW
I
SW
V
EN
I
EN
f
SW
V
D
I
RD
V
OVP
Maximum Duty Cycle
Switch Current Limit
Switch Saturation Voltage
Switch Leakage Current
Enable Threshold
Enable Pin Current
Oscillator Frequency
Schottky Forward Drop
Schottky Leakage Current
Overvoltage Protection
I
D
= 150mA
V
R
= 30V
MIC2289-15
MIC2289-24
MIC2289-34
Hysteresis
13
21
30
14
22.5
32
150
10
I
SW
= 0.5A
V
EN
= 0V, V
SW
= 10V
TURN ON
TURN OFF
V
EN
= 10V
1.05
1.5
0.4
20
1.2
0.8
40
1.35
1
4
16
24
34
V
FB
> 200mV, (not switching)
V
EN
= 0V
(5)
(±5%)
V
FB
= 95mV
3V
≤
V
IN
≤
5V
5mA
≤
I
OUT
≤
20mA
85
90
Condition
Min
2.5
1.8
2.1
2.5
0.1
95
–450
0.5
0.5
90
750
450
0.01
5
1
2
Typ
Max
10
2.4
5
1
100
Units
V
V
mA
µA
mV
nA
%
%
%
mA
mV
µA
V
V
µA
MHz
V
µA
V
V
V
°C
°C
T
J
Notes:
Overtemperature
Threshold Shutdown
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. This device is not guaranteed to operate beyond its specified operating rating.
3. Devices are inherently ESD sensitive. Handling precautions required. Human body model.
4. Specification for packaged product only.
5. I
SD
= I
VIN
.
August, 2004
3
M9999-081104
MIC2289
Micrel
Typical Characteristics
Feedback Voltage
vs. Input Voltage
100
99
98
97
96
95
94
93
92
91
90
SHUTDOWN CURRENT (µA)
Shutdown Current
vs. Input Voltage
5
4
3
2
1
0
QUIESCENT CURRENT (mA)
Quiescent Current
vs. Input Voltage
5
4
3
2
1
0
FB VOLTAGE (mV)
0
2
4
6
V
IN
(V)
8
10
12
0
2
4
6
V
IN
(V)
8
10
12
0
2
4
6
V
IN
(V)
8
10
12
SWITCHING FREQUENCY (MHz)
1.4
1.2
IENABLE (µA)
50
45
40
35
I = 10V
30
EN
25
20
15
10
SCHOTTKY FORWARD CURRENT (mA)
Switch Frequency
vs. Temperature
EN Pin Bias Current
vs. Temperature
Schottky Forward
Voltage Drop
700
600
500
400
300
200
100
1
0.8
0.6
0.4
0.2
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
I
EN
= 4.2V
I
EN
= 3.6V
1050
SCHOTTKY FORWARD VOLTAGE DROP (mV)
SCHOTTKY LEAKAGE CURRENT (µA)
Schottky Reverse
Leakage Current
2.5
SATURATION VOLTAGE (mV)
2
1.5
1
0.5
V
R
= 10V
0
30
40
50 60 70 80 90 100
TEMPERATURE (°C)
V
R
= 25V
550
500
450
400
350
300
-40
Saturation Voltage
vs. Temperature
900
CURRENT LIMIT (mA)
850
800
750
700
650
Current Limit
vs. Temperature
V
R
= 16V
I
SW
= 500mA
0
40
80
TEMPERATURE (°C)
120
V
IN
= 2.5V
600
-40
0
40
80
TEMPERATURE (°C)
120
Switch Saturation Voltage
vs. Current
600
SATURATION VOLTAGE (mV)
500
400
300
200
100
0
0
100
200 300
I
SW
(mA)
400
500
V
IN
= 5V
V
IN
= 2.5V
M9999-081104
4
August, 2004
1150
5 I = 3.0V
EN
0
-50
0
50
TEMPERATURE (°C)
450
550
650
750
850
950
100
0
MIC2289
Micrel
Functional Diagram
VIN
FB
EN
OUT
OVP
SW
g
m
V
REF
95mV
Σ
PWM
Generator
1.2MHz
Oscillator
Ramp
Generator
GND
MIC2289 Block Diagram
Functional Description
The MIC2289 is a constant frequency, PWM current mode
boost regulator. The block diagram is shown above. The
MIC2289 is composed of an oscillator, slope compensation
ramp generator, current amplifier, g
m
error amplifier, PWM
generator, 500mA bipolar output transistor, and Schottky
rectifier diode. The oscillator generates a 1.2MHz clock. The
clock’s two functions are to trigger the PWM generator that
turns on the output transistor and to reset the slope compen-
sation ramp generator. The current amplifier is used to
measure the switch current by amplifying the voltage signal
from the internal sense resistor. The output of the current
amplifier is summed with the output of the slope compensa-
tion ramp generator. This summed current-loop signal is fed
to one of the inputs of the PWM generator.
The g
m
error amplifier measures the LED current through the
external sense resistor and amplifies the error between the
detected signal and the 95mV reference voltage. The output
of the g
m
error amplifier provides the voltage-loop signal that
is fed to the other input of the PWM generator. When the
current-loop signal exceeds the voltage-loop signal, the
PWM generator turns off the bipolar output transistor. The
next clock period initiates the next switching cycle, maintain-
ing the constant frequency current-mode PWM control. The
LED is set by the feedback resistor:
95mv
I
LED
=
R
FB
The Enable pin shuts down the output switching and disables
control circuitry to reduce input current to leakage levels.
Enable pin input current is zero at zero volts.
5
August, 2004
M9999-081104
京公网安备 11010802033920号
EEWORLD
