MP3202
1.3A Fixed Frequency
White LED Driver
The Future of Analog IC Technology
DESCRIPTION
The MP3202 is a step-up converter designed for
driving up to 39 white LEDs (13 strings of 3 LEDs
each) from a 5V system rail. The MP3202 uses a
current mode, fixed frequency architecture to
regulate the LED current, which is measured
through an external current sense resistor. Its low
104mV feedback voltage reduces power loss and
improves efficiency. The OV pin monitors the
output voltage and turns off the converter if an
over-voltage condition is present due to an open
circuit condition.
The MP3202 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload.
The MP3202 is available in small 6-pin TSOT23
or 8-pin QFN (2mm x 2mm) packages.
FEATURES
•
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•
•
•
•
•
•
•
•
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•
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•
2.5V to 6V Input Voltage Range
On Board Power MOSFET
Drives up to 39 White LEDs at 5V Input
Up to 92% Efficiency
Over 1MHz Fixed Switching Frequency
Open Load Shutdown
Low 104mV Feedback Voltage
Soft-Start/PWM Dimming
UVLO, Thermal Shutdown
Internal 1.3A Current Limit
Available in TSOT23-6 and QFN8 Packages
Cell Phones
Handheld Computers and PDAs
Digital Still Cameras
Small LCD Displays
APPLICATIONS
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
V
IN
4.5V - 6V
Efficiency vs
Input Voltage
100
I
OUT
=100mA
EFFICIENCY (%)
13 Strings
IN
SW
90
80
70
60
50
4.0
I
OUT
=180mA
EN
EN
MP3202
OV
FB
GND
4.5
5.0
5.5
INPUT VOLTAGE (V)
6.0
MP3202 Rev. 0.91
9/21/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
1
MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER
PACKAGE REFERENCE
TOP VIEW
SW
GND
FB
1
2
3
6
5
4
IN
OV
EN
TOP VIEW
GND
IN
OV
EN
1
2
3
4
8
7
6
5
SW
NC
FB
GND
Part Number*
MP3202DJ
*
Package
TSOT23-6
Temperature
–40°C to +85°C
Part Number**
MP3202DG
Package
Temperature
QFN8
–40°C to +85°C
(2mm x 2mm)
For Tape & Reel, add suffix –Z (eg. MP3202DJ–Z)
For RoHS compliant packaging, add suffix –LF
(eg. MP3202DJ–LF–Z)
**
For Tape & Reel, add suffix –Z (eg. MP3202DG–Z)
For RoHS compliant packaging, add suffix –LF
(eg. MP3202DG–LF–Z)
ABSOLUTE MAXIMUM RATINGS
(1)
SW Pin......................................–0.5V to +28.5V
All Other Pins ..............................–0.3V to +6.5V
Storage Temperature.............. –55°C to +150°C
Thermal Resistance
(3)
TSOT23-6.............................. 220 .... 110..
°C/W
QFN8 (2mm x 2mm) ............... 80 ...... 16...
°C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
operating conditions.
3) Measured on approximately 1” square of 1 oz copper.
θ
JA
θ
JC
Recommended Operating Conditions
(2)
IN Supply Voltage ..............................2.5V to 6V
Output Voltage ....................................V
IN
to 25V
Operating Temperature............. –40°C to +85°C
ELECTRICAL CHARACTERISTICS
V
IN
= V
EN
= 5V, T
A
= +25°C, unless otherwise noted.
Parameters
Operating Input Voltage
Supply Current (Shutdown)
Supply Current (Quiescent)
Switching Frequency
Maximum Duty Cycle
Under Voltage Lockout
IN Under Voltage Lockout
Under Voltage Lockout
Hysteresis
Open Lamp Shutdown
Threshold
Symbol Condition
V
IN
V
EN
= 0V
V
FB
= 0.15V
f
SW
V
FB
= 0V
UVLO
V
IN
Rising
1.0
85
Min
2.5
0.1
690
1.3
92
2.25
92
V
OV
V
OV
Rising
28
Typ
Max
6
1
750
1.5
Units
V
µA
µA
MHz
%
V
mV
V
2.45
MP3202 Rev. 0.91
9/21/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
2
MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER
ELECTRICAL CHARACTERISTICS
(continued)
V
IN
= V
EN
= 5V, T
A
= +25°C, unless otherwise noted.
Parameters
Enable
EN Threshold
EN Threshold
EN Hysteresis
EN Input Bias Current
Feedback
FB Voltage
FB Input Bias Current
Output Switch
SW On-Resistance
(4)
SW Current Limit
(4)
Thermal Shutdown
(4)
Symbol Condition
V
EN
Rising, V
IN
= 5V
V
EN
Rising, V
IN
= 2.5V
V
EN
= 0V, 5V
Min
1.0
0.8
Typ
1.35
90
Max
1.6
Units
V
V
mV
µA
mV
nA
Ω
A
°C
1
94
–600
104
–300
0.5
1.33
160
114
V
FB
= 0.1V
R
ON
Duty Cycle = 60%
Notes:
4) Guaranteed by design.
PIN FUNCTIONS
TSOT23-6
Pin #
1
2
3
QFN8
Pin #
8
1, 5
6
Name Description
SW
GND
FB
Power Switch Output. SW is the drain of the internal MOSFET switch. Connect
the power inductor and output rectifier to SW. SW can swing between GND and
25V.
Ground.
Feedback Input. The MP3202 regulates the voltage across the current sense
resistor between FB and GND. Connect a current sense resistor from the bottom
of the LED string to GND. Connect the bottom of the LED string to FB. The
regulation voltage is 104mV.
Regulator On/Off Control Input. A high input at EN turns on the converter, and a
low input turns it off. When not used, connect EN to the input source for automatic
startup.
The EN pin cannot be left floating.
Over Voltage Input. OV measures the output voltage for open circuit protection.
Connect OV to the output at the top of the LED string.
Input Supply Pin. Must be locally bypassed.
No Connect.
4
5
6
4
3
2
7
EN
OV
IN
NC
MP3202 Rev. 0.91
9/21/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
3
MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER
OPERATION
The MP3202 uses a constant frequency, peak
current mode boost regulator architecture to
regulate the strings of white LEDs. Refer to the
block diagram in Figure 1 for details.
At the start of each oscillator cycle the FET is
turned on through the control circuitry. To
prevent sub-harmonic oscillations at duty cycles
greater than 50%, a stabilizing ramp is added to
the output of the current sense amplifier and the
result is fed into the positive input of the PWM
comparator. When this voltage equals the
output voltage of the error amplifier the power
FET is turned off.
The voltage at the output of the error amplifier
is an amplified version of the difference
between the 104mV reference voltage and the
feedback voltage. In this way the peak current
level keeps the output in regulation.
If the feedback voltage starts to drop, the output
of the error amplifier increases. This results in
more current flowing through the power FET,
thus increasing the power delivered to the
output.
FB
+
-
-
+
AMPLIFIER
CONTROL
LOGIC
M1
SW
104mV
PWM
COMPARATOR
-
+
+
CURRENT
SENSE
AMPLIFIER
1.3MHz
OSC
GND
Figure 1—Functional Block Diagram
MP3202 Rev. 0.91
9/21/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
4
MP3202 – 1.3A FIXED FREQUENCY WHITE LED DRIVER
APPLICATION INFORMATION
V
IN
4V to 6V
MBR0520
9 Strings
Total
IN
SW
OFF ON
EN
MP3202
OV
FB
GND
Figure 2—Circuit for Driving 27 WLEDs
A typical application circuit is provided in Figure
2. The 27 white LEDs can be driven from a
voltage supply range of 4V to 6V at a total
output current of 180mA. A 2.2µF output
capacitor is sufficient for most applications but
up to 1µF may be used. A 10µH inductor with
low DCR (inductor resistance) is recommended
to improve efficiency. A 4.7µF ceramic
capacitor is recommended for the input
capacitance in the real system. Schottky diodes
with fast recovery and a low forward voltage are
recommended. Schottky diodes with a 500mA
rating are sufficient for the MP3202. The
switching
characteristics
during
normal
operation can be seen in Figure 3. The MP3202
has internal soft-start to limit the amount of
current through the IN pin at startup and to also
limit the amount of overshoot on the output. The
current limit is increased by a fourth every 40µs
giving a total soft-start time of 120µs.
Steady State Operation
V
IN
= 5V, 27 LEDS, 180mA
V
SW
5V/div.
V
OUT AC
200mV/div.
I
L
500mA/div.
400ns/div.
Figure 3—Steady State Operation
Figure 4 shows the startup behavior of the
MP3202. The ramped voltage added to the
current sense amplifier reduces the current
output as the duty cycle increases. As more
LEDs are added, the output voltage rises but
the current that can be delivered to the load is
reduced as well.
MP3202 Rev. 0.91
9/21/2007
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2007 MPS. All Rights Reserved.
5
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