MP1528
9 Lamp, 36V Precision White LED Driver
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The MP1528 is a step-up converter designed
for driving up to nine (9) series White LEDs
(LED) from a single cell Lithium-Ion battery. It
regulates the LED current and includes an
analog input for varying the LED brightness.
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•
•
•
•
•
•
•
•
•
•
The MP1528 uses current limited, variable
frequency architecture to regulate the LED
current while maintaining high efficiency. The
BIAS pin measures the output voltage and turns
off the converter if an over voltage condition is
present to prevent damage due to an open
circuit condition. The LED current is measured
with an external current sense resistor. The low
0.4V full-scale regulation threshold and 0.63Ω
power switch minimize power loss.
The MP1528 is available in an 8-pin MSOP, an
8-pin 2mm x 2mm QFN and a 6-pin 3mm x
3mm QFN packages.
EVALUATION BOARD REFERENCE
Board Number
Dimensions
EV1528DQ-00A
2.0” x 1.5” x 0.5”
Drives up to 9 Series White LEDs
Integrated 0.63Ω Power MOSFET
Low 0.4V Full-Scale Current Sense Threshold
Over 20mA Output Current Capacity
Analog and Digital PWM Brightness Control
Open Load Shutdown
Soft-Start
Internal Current Limit
Under Voltage Lockout
Thermal Shutdown
Available in 8-Pin MSOP, 8-pin 2mm x 2mm
QFN and 6-Pin 3mm x 3mm QFN Packages
APPLICATIONS
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Handheld Computers
PDAs
PDA Phones
Digital and Video Cameras
Small LCD Displays
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs
LED Current
D1
B160B
VIN
100
LED1
BRT
5
6
2
SW
EN
MP1528
BRT
BIAS
GND
FB
3
4
C3
10nF
LED9
1
6 LEDs
80
8 LEDs
70
9 LEDs
60
50
40
30
MP1528_TAC01
MP1528 Rev. 1.9
1/25/2010
7 LEDs
90
EFFICIENCY (%)
EN
VIN = 12V
0
5
10 15 20 25 30
LED CURRENT (mA)
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35
MP1528_EC01
1
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
ORDERING INFORMATION
Part Number*
Package
Top Marking
Temperature
MP1528DQ
QFN6 (3mm x 3mm)
A6YW
Part Number**
Package
Top Marking
–40°C to +85°C
Temperature
MP1528DK
MSOP8
1528D
Part Number***
Package
Top Marking
–40°C to +85°C
Temperature
MP1528DG
QFN8 (2mm x 2mm)
A6Y
–40°C to +85°C
*For Tape & Reel, add suffix –Z (e.g. MP1528DQ–Z). For RoHS compliant packaging, add suffix –LF (e.g.
MP1528DQ–LF–Z)
**For Tape & Reel, add suffix –Z (e.g. MP1528DK–Z). For RoHS compliant packaging, add suffix –LF (e.g.
MP1528DK–LF–Z)
***For Tape & Reel, add suffix –Z (e.g. MP1528DG–Z). For RoHS compliant packaging, add suffix –LF (e.g.
MP1528DG–LF–Z)
PACKAGE REFERENCE
TOP VIEW
TOP VIEW
FB
GND
SW
1
6
2
5
3
4
TOP VIEW
BRT
EN
BIAS
NC
1
8
NC
FB
2
7
BRT
GND
3
6
EN
SW
4
5
BIAS
EXPOSED PAD
ON BACKSIDE
N/C
1
8
N/C
FB
2
7
BRT
GND
3
6
EN
SW
4
5
BIAS
EXPOSED PAD
ON BACKSIDE
QFN6
MSOP8
QFN8
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
Supply Voltage VBIAS to GND ....................... 42V
VSW to GND..................................–0.5V to +42V
VEN, VBRT, VFB to GND ....................–0.3V to +6V
Continuous Power Dissipation
(TA = +25°C)(2)
QFN6 (3mm x 3mm) .................................. 2.5W
QFN8 (2mm x 2mm) .................................. 1.6W
MSOP8 .................................................... 0.83W
Storage Temperature.............. –65°C to +150°C
QFN6 (3mm x 3mm) ............... 50 ...... 14... °C/W
QFN8 (2mm x 2mm) ............... 80 ...... 16... °C/W
MSOP8 .................................. 150 ..... 65... °C/W
Recommended Operating Conditions
(3)
Supply Voltage VBIAS ........................2.7V to 36V
Operating Temperature............. –40°C to +85°C
MP1528 Rev. 1.9
1/25/2010
(4)
θJA
θJC
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ(MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD(MAX)=(TJ(MAX)TA)/ θJA. 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 board.
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© 2010 MPS. All Rights Reserved.
2
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
ELECTRICAL CHARACTERISTICS
VBIAS = VEN = 5.0V, VBRT = 1.2V, TA = +25°C, unless otherwise noted.
Parameter
Symbol
Supply Current (Shutdown)
Supply Current (Quiescent)
Minimum Off Time (Normal
Operation)
Minimum Off Time (Startup)
Under Voltage Lock Out
BIAS Under Voltage Lock Out
UVLO
MP1528 Rev. 1.9
1/25/2010
VBIAS Rising,
100mV Hysteresis
Measured at BIAS
VBIAS = 20V, VEN < 0.4V
VBIAS = 40V, VEN < 0.4V
VFB
Typ
Max
Units
1
650
3
800
µA
µA
330
ns
1.2
µs
2.1
0.8
Bias Current
Thermal Shutdown
Min
VEN < 0.4V
VEN > 2.0V, BRT = GND
Enable
EN High Threshold
EN Hysteresis
EN Input Leakage Current
Open Load Shutdown
Threshold
Feedback Comparator
FB Regulation Threshold
FB Hysteresis
FB Input Leakage Current
PWM Mode Using BRT
Output-Off Threshold
BRT Input Leakage Current
BRT Full-Scale Threshold
Output Switch
SW On-Resistance
SW Current Limit
Condition
1.2
60
2.65
V
1.5
150
V
mV
nA
5
100
V
µA
µA
40
70
VBRT = 1.2V
0.38
VFB = 0.2V
–150
VBRT = 0.6V
0.18
–100
0.40
10
–80
0.42
V
mV
nA
0.27
V
nA
V
1.2
RON
VBIAS = 5.0V
0.63
950
Ω
mA
160
°C
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3
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
TYPICAL PERFORMANCE CHARACTERISTICS
Circuit on front page, VIN = 3.6V, 9 LEDs, ILED = 20mA, VBRT = 1.2V, TA = +25°C, unless otherwise
noted.
Feedback Voltage vs
BRT Voltage
430
500
420
400
LED Current vs
BRT Duty Cycle @ 200Hz
20
410
400
390
LED CURRENT (mA)
18
FB VOLTAGE (mV)
FB VOLTAGE (mV)
Feedback Voltage vs
Input Voltage
300
200
100
380
3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
0
5.5
0
1
2
3
4
BRT VOLTAGE (V)
MP1528_TPC01
10
8
6
4
VSW
10V/div.
IINDUCTOR
0.5A/div.
VBIAS
10V/div.
VSW
20V/div.
VBIAS
20V/div.
Efficiency vs
LED Current
70
60
50
100
VIN =
90
EFFICIENCY (%)
80
(8 LEDs)
80
70
60
50
40
40
5
10
15
20
LED CURRENT (mA)
25
MP1528_TPC07
MP1528 Rev. 1.9
1/25/2010
30
(9 LEDs)
VIN =
90
12V
7.5V
5V
4.2V
3V
EFFICIENCY (%)
VIN =
0
MP1528_TPC06
Efficiency vs
LED Current
100
100
Startup into an
Open Load
MP1528_TPC05
Efficiency vs
LED Current
12V
7.5V
5V
4.2V
3V
20
40
60
80
BRT DUTY CYCLE (%)
VEN
5V/div.
MP1528_TPC04
(6 LEDs)
0
MP1528_TPC03
Startup
VSW
10V/div.
VBIAS AC
0.2V/div.
90
0
5
VEN
5V/div.
EFFICIENCY (%)
12
MP1528_TPC02
Steady-State Operation
30
14
2
370
2.5
100
16
12V
7.5V
5V
4.2V
3V
80
70
60
50
40
0
5
10
15
20
LED CURRENT (mA)
25
30
0
5
10
15
20
LED CURRENT (mA)
MP1528_TPC08
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25
MP1528_TPC09
4
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
PIN FUNCTIONS
QFN6
Pin #
MSOP8
QFN8
Name
1
2
2
FB
2
3
3
GND
3
4
4
SW
4
5
5
BIAS
5
6
6
EN
6
7
7
BRT
1, 8
1, 8
NC
MP1528 Rev. 1.9
1/25/2010
Description
Feedback Input. The MP1528 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 and connect
the bottom of the LED string to FB. The regulation threshold is set at
0.4V for VBRT ≥ 1.2V.
Ground.
Power Switch Output. SW is the drain of the internal MOSFET
switch. Connect the power inductor and output rectifier to SW, which
can swing between GND and 42V.
Internal Power Input. BIAS powers the internal circuitry and
measures the output voltage for open circuit protection. Connect
BIAS to the output at the top of the LED string. If open circuit
protection is not required, BIAS may be connected to the input
source to reduce power consumption of the MP1528.
Regulator On/Off Control Input. A high voltage applied to EN turns on
the converter; a low voltage turns it off. When not used, connect EN
to the input source for automatic startup. If EN is driven over 6V,
place a 100kΩ resistor in series with EN. Never leave EN floating.
Analog or PWM Input for Controlling LED Brightness. When used in
analog mode, apply a DC voltage of 0.27V to 1.2V. This input voltage
is attenuated by 1/3 to set the voltage across the sense resistor at
FB. Maximum brightness (20mA) occurs with an application of 1.2V.
To control the brightness in PWM mode, apply a PWM signal with a
minimum voltage less than 0.18V and a maximum voltage greater
than 1.2V (when a voltage less than 0.18V is applied to this pin, the
output switch is turned off). The regulator operates at maximum
brightness when more than 1.2V is applied. The frequency of the
PWM signal must be between 100Hz to 400Hz.
No Connect
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5
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
OPERATION
BIAS
4
EN
5
INTERNAL
REGULATOR
& ENABLE
CIRCUIT
UVLO &
THERMAL
SHUTDOWN
3 SW
29V
OPEN LOAD
SHUTDOWN
COMPARATOR
2 GND
330ns
ONE-SHOT
TIMER
FEEDBACK
COMPARATOR
BRT
6
+
-CURRENT LIMIT
COMPARATOR
+
--
1.23V
CONTROL
LOGIC &
OUTPUT
DRIVER
+
--
0.6V
1 FB
+
--
+
-1.2V
MP1528_F01_BD01
Figure 1—Functional Block Diagram
The MP1528 utilizes a constant off-time control
scheme. For maximum brightness, the BRT pin
is biased at or above 1.2V. Its voltage is routed
through the unity gain buffer whose output is
clamped at 1.2V. A resistor divider from the
buffer to the inverting input of the feedback
comparator divides the BRT voltage by three to
set the current sense threshold. If the FB pin
voltage is lower than this threshold the power
MOSFET is turned on. The MOSFET and
inductor currents increase until the current limit
comparator trips at 950mA, turning off the
MOSFET for at least 330ns. At the end of the
330ns, if the FB pin is still lower than the
current sense threshold, the MOSFET is turned
on again.
Analog Brightness Adjust
Analog
brightness
adjustments
are
accomplished by applying a voltage between
0.27V to 1.2V on the BRT pin.
MP1528 Rev. 1.9
1/25/2010
PWM Brightness Adjust
PWM brightness adjustments are accomplished
by driving the BRT pin with a digital signal
whose low voltage is below 0.18V and high
voltage is greater than 1.2V. A voltage below
0.18V forces the power MOSFET to turn off. A
voltage greater than 1.2V will cause the FB pin
to regulate at 0.4V.
Open Load Shutdown
Open Load Shutdown is implemented by
connecting the BIAS pin to the top of the LED
string. In the fault condition where the
connection to the LED is open, VOUT will rise up,
as the FB pin has no voltage. Once VOUT
exceeds 40V, the MP1528 will cease operation
until the EN pin is cycled off and on. Connecting
the BIAS pin to the input will disable Open Load
Shutdown.
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6
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
APPLICATION INFORMATION
Setting the LED Current
The LED current is set by the voltage at BRT
(VBRT) and the sense resistor (R1) at FB. The
VBRT range for adjusting the LED current is
0.27V to 1.2V. Over this range, the LED current
can be calculated as:
ILED =
VBRT
3 × R1
Voltages greater than 1.2V can be applied to
BRT. Use 1.2V in the equation if VBRT ≥ 1.2V or
the BRT pin is left open.
For example, the LED current is set to 20mA if
VBRT ≥ 1.2V (or left open) and R1 = 20Ω.
Capacitor Selection
A 4.7µF to 10µF ceramic input capacitor (C1)
and a 0.47µF to 1µF ceramic output capacitor
(C2) are recommended for most applications. A
capacitor (C3, typically 1nF to 10nF) in parallel
with the LED string improves stability, input
ripple and output ripple, especially when large
inductance values (10µH or above) are used.
For the best stability over a wide temperature
range, use capacitors with a X5R or X7R
dielectric.
Inductor Selection
The MP1528 has a 950mA inductor current limit
and can drive up to 9 LEDs at 20mA.
Inductance values (for L1) from 4.7µH to 22µH
will work as well. 6.2µH or 6.8µH is a good
choice for high efficiency and small size. To
prevent saturation, use an inductor with a
saturation current rating that is higher than the
device current limit.
Diode Selection
The MP1528’s high switching frequency
demands a high speed rectifier (D1) for
optimum efficiency. A Schottky diode is
recommended due to its fast recovery time and
low forward voltage drop. Ensure the diode’s
average and peak current ratings exceed the
average output current and peak inductor
current. In addition, the diode’s reverse
breakdown voltage must exceed the output
voltage.
Layout
Careful PC board layout is required due to fast
switching. All components must be placed as
close to the IC as possible. Keep the path
between the inductor L1, diode D1, and output
capacitor C2 extremely short for minimal noise
and ringing. The feedback components such as
the sense resistor R1 must be kept close to the
FB pin to prevent noise injection on the FB pin
trace. The ground return of C1 and C2 should
be tied close to the GND pin. See the MP1528
demo board layout for reference.
D1
B160B
5V-18V
VIN
LED1
EN
BRT
5
6
2
SW
EN
MP1528
BRT
BIAS
GND
FB
3
4
8 LEDs
per string
C3
10nF
LED8
1
Figure 2—Driving 3 Strings of 8 LEDs in Series (60mA Total Current)
MP1528 Rev. 1.9
1/25/2010
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7
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
PACKAGE INFORMATION
MSOP8
MP1528 Rev. 1.9
1/25/2010
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© 2010 MPS. All Rights Reserved.
8
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
QFN6 (3mm x 3mm)
2.90
3.10
0.35
0.55
PIN 1 ID
MARKING
0.35
0.45
1.40
1.60
PIN 1 ID
SEE DETAIL A
1
6
2.90
3.10
PIN 1 ID
INDEX AREA
2.20
2.40
0.95
BSC
3
4
TOP VIEW
BOTTOM VIEW
PIN 1 ID OPTION A
R0.20 TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.80
1.00
0.20 REF
0.00
0.05
SIDE VIEW
DETAIL A
NOTE:
2.90
0.80
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX.
4) JEDEC REFERENCE IS MO-229, VARIATION VEEA-2.
5) DRAWING IS NOT TO SCALE.
1.50
0.40
2.30
0.95
RECOMMENDED LAND PATTERN
MP1528 Rev. 1.9
1/25/2010
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9
MP1528 – 9 LAMP, 36V PRECISION WHITE LED DRIVER
QFN8 (2mm x 2mm)
PIN 1 ID
MARKING
1.90
2.10
0.25
0.45
0.18
0.30
1.90
2.10
PIN 1 ID
INDEX AREA
PIN 1 ID
SEE DETAIL A
0.45
0.65
8
1
1.05
1.25
0.50
BSC
5
TOP VIEW
4
BOTTOM VIEW
0.80
1.00
PIN 1 ID OPTION A
0.30x45º TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.20 REF
0.00
0.05
SIDE VIEW
DETAIL A
NOTE:
1.90
0.70
0.60
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX.
4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VCCD-3.
5) DRAWING IS NOT TO SCALE.
0.25
1.20
0.50
RECOMMENDED LAND PATTERN
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS
products into any application. MPS will not assume any legal responsibility for any said applications.
MP1528 Rev. 1.9
1/25/2010
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
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