TM
MP1518
Fixed Frequency
White LED Driver
The Future of Analog IC Technology
TM
DESCRIPTION
The MP1518 is a step-up converter designed for
driving up to 6 series white LEDs from a single
cell Lithium Ion battery. The MP1518 uses 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 MP1518 includes under-voltage lockout,
current limiting and thermal overload protection
preventing damage in the event of an output
overload.
The MP1518 is available in small 6-pin TSOT23
or 8-pin QFN (2mm x 2mm) packages.
Also available is the MP1518DJE, which has
slightly slower switching slew rate, thus is ideal
for applications where low EMI is critical.
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
•
•
On Board Power MOSFET
Drives up to 6 Series White LEDs
Up to 87% Efficiency
Over 1MHz Fixed Switching Frequency
Open Load Shutdown
Low 104mV Feedback Voltage
Soft-Start/PWM Dimming
UVLO, Thermal Shutdown
Internal Current Limit
Available in TSOT23-6 and QFN8 Packages
Cell Phones
Handheld Computers and PDAs
Digital Still Cameras
Small LCD Displays
APPLICATIONS
All MPS parts are lead-free and adhere to the RoHS directive. For MPS green
status, please visit MPS website under Quality Assurance. “MPS” and “The
Future of Analog IC Technology” are Trademarks of Monolithic Power Systems,
Inc.
EVALUATION BOARD REFERENCES
Board Number
EV0056
EV1518DG-00A
Dimensions
1.9”X x 1.8”Y x 0.4”Z
2.0”X x 1.8”Y x 0.4”Z
TYPICAL APPLICATION
V
IN
5V
LED1
LED2
EFFICIENCY (%)
Efficiency vs
LED Current
88
4 LEDS
86
84
82
80
78
76
5
V
IN
= 3.6V
10
15
LED CURRENT (mA)
20
6 LEDS
3 LEDS
LED3
LED4
IN
SW
EN
EN
MP1518
OV
FB
LED5
LED6
GND
MP1518 Rev. 1.61
4/18/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
1
TM
MP1518 – FIXED FREQUENCY WHITE LED DRIVER
ORDERING INFORMATION
Part Number
MP1518DJ*
MP1518DJE
MP1518DG**
Package
TSOT23-6
QFN8 (2x2mm)
Top Marking
A8
F6
A8
* For Tape & Reel, add suffix –Z (e.g. MP1518DJ–Z);
For RoHS, compliant packaging, add suffix –LF (e.g. MP1518DJ–LF–Z).
* For Tape & Reel, add suffix –Z (e.g. MP1518DG–Z);
For RoHS, compliant packaging, add suffix –LF (e.g. MP1518DG–LF–Z).
PACKAGE REFERENCE
TOP VIEW
SW
GND
FB
1
2
3
6
5
4
IN
OV
TOP VIEW
GND
IN
OV
EN
1
2
3
4
8
7
6
5
SW
NC
FB
GND
EN
TSOT23-6
QFN8 (2mm x 2mm)
ABSOLUTE MAXIMUM RATINGS
(1)
SW, OV Pins................................–0.5V to +28V
All Other Pins ..............................–0.3V to +6.5V
(2)
Continuous Power Dissipation (T
A
= +25°C)
TSOT23-6…………………………………....0.57W
QFN8 (2x2mm)……………………………....1.6W
Storage Temperature.............. –55°C to +150°C
Thermal Resistance
(4)
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 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 continuous power dissipation at
any ambient temperature is calculated by P
D
(MAX) = (T
J
(MAX)-T
A
)/θ
JA
. Exceeding the maximum allowable power
dissipation will cause excessive die temperature, and the
regulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
θ
JA
θ
JC
Recommended Operating Conditions
(3)
IN Supply Voltage ..............................2.5V to 6V
Output Voltage ....................................V
IN
to 25V
Operating Junction Temp. (T
J
). -40°C to +125°C
MP1518 Rev. 1.61
4/18/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
2
TM
MP1518 – FIXED FREQUENCY WHITE LED DRIVER
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
Enable
EN Threshold
EN Threshold
EN Hysteresis
EN Input Bias Current
Feedback
FB Voltage
FB Input Bias Current
Output Switch
SW On-Resistance
(5)
SW Current Limit
(5)
Thermal Shutdown
(5)
Notes:
5) Guaranteed by design.
Symbol
V
IN
Condition
V
EN
= 0V
V
FB
= 0.15V
Min
2.5
Typ
0.1
690
1.3
92
2.25
92
Max
6
1
750
1.5
Units
V
µA
µA
MHz
%
V
mV
V
f
SW
V
FB
= 0V
UVLO
V
IN
Rising
1.0
85
2.45
V
OV
V
OV
Rising
V
EN
Rising
V
EN
Rising, V
IN
= 2.5V
V
EN
= 0V, 5V
94
-600
1.0
0.8
28
1.35
90
1
104
-300
0.5
350
160
114
1.6
V
V
mV
µA
mV
nA
Ω
mA
°C
V
FB
= 0.1V
R
ON
Duty Cycle = 60%
MP1518 Rev. 1.61
4/18/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
3
TM
MP1518 – FIXED FREQUENCY WHITE LED DRIVER
PIN FUNCTIONS
TSOT23-6
Pin #
1
2
3
QFN8
Pin #
8
1, 5
6
Name Pin Function
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 MP1518 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.
4
5
6
4
3
2
EN
OV
IN
MP1518 Rev. 1.61
4/18/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
4
TM
MP1518 – FIXED FREQUENCY WHITE LED DRIVER
OPERATION
The MP1518 uses a constant frequency, peak
current mode boost regulator architecture to
regulate the series string of white LEDs. The
operation of the MP1518 can be understood by
referring to the block diagram of Figure 1.
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 percent, 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
MP1518 Rev. 1.61
4/18/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
5
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