POWER MANAGEMENT
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Highly Integrated Step-Up Converter for
White LED Applications in MLPD-W8-2x2
SC4509
POWER MANAGEMENT
1
Description Features
Applications
Typical Application Circuit
March 26, 2007
L1
22μH
R1
LED3
U2
SC4509
SW 6
VIN
5
EN/SS
4
GND
2
FB 3
VOUT 1
Vin
LED4
LED2
Vo
C2
0.22μF
C1
1μF
EN/SS
LED1
Digital Video Cameras
White LED Backlight Driver
OLED Display Driver
Portable Media Players
GPS Receivers
Cellular Phones
PDAs and Handheld Computers
VIN range: 2.7V — 10V
Integrated Schottky diode
81% effi ciency
Requires only 4 external components
Up to 20V of output voltage
30mA maximum LED current
Open LED protection (OVP)
1.2MHz PWM switching frequency
Low feedback voltage (20OmV typical)
Wide range of PWM dimming
Drives up to 5 LEDs
500mA switch current limit
220nF output capacitor
Available in 2mm x 2mm x 0.75mm MLPD-W8 and
SOT23-6 packages
Packages are fully WEEE and RoHS compliant
The SC4509 is a highly integrated step-up DC/DC convert-
er targeted for white LED backlighting applications. It is
designed to drive up to fi ve LEDs with a wide input voltage
range of 2.7 to 10 volts. Designed for 20V output voltage,
the SC4509 operates with a constant 1.2MHz PWM fre-
quency. To optimize effi ciency, the feedback voltage is set
to only 199mV, minimizing the power loss in the current
setting resistor. The product requires only four external
components (CIN, COUT, L and RSET), making it ideal for
applications that require low cost and minimal PCB area.
The SC4509 offers current limit and over-voltage protec-
tion (OVP) to safeguard the device under extreme operat-
ing conditions. If the LEDs become disconnected or fail in
an open state condition, OVP circuitry will be activated to
shut down the device. The EN/SS pin allows the device
to be placed in power-down mode, disabling the control
circuitry to reduce input current.
© 2007 Semtech Corp.
SC4509
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PRELIMINARY
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2
Absolute Maximum Rating
Electrical Characteristics
Parameter Symbol Maximum Units
Input Supply Voltage VIN -0.3 to 20 V
SW Voltage VSW -0.3 to 30 V
Maximum Output Voltage VOUT 30 V
Feedback Voltage VFB -0.3 to 20 V
EN/SS Voltage VEN/SS -0.3 to VIN + 0.3 V
Maximum Junction Temperature TJ125 °C
Storage Temperature Range TSTG -65 to +150 °C
Thermal Impedance
Junction to Ambient(1)
MLPD-W8
θJA
78
C/W
SOT23-6 165
Lead Temperature (Soldering), 10s (SOT23-6 package only) TLEAD 300 °C
Peak IR Flow Temperature, (10-40sec) TPKG 260 °C
ESD Rating (Human Body Model)(2) VESD 2kV
Exceeding the specifi cations below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specifi ed in the
Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability.
Unless specifi ed: VIN = VEN/SS = 3.6V; CIN = 1μF; COUT = 0.22μF; L = 22μH; unless otherwise noted, TA = +25°C for Typ, -40ºC to 85°C for Min and Max.
Parameter Symbol Conditions Min Typ Max Units
Input Voltage VIN 2.7 10 V
Quiescent Current IQNo switching 2.6 3.3 mA
Feedback Voltage VFB 182 199 216 mV
Feedback Pin Bias Current IQFB 35 100 nA
Switching Frequency fOSC TA=25 °C 1.0 1.2 1.4 MHz
Maximum Output Voltage VOUT 20 V
Switch Saturation Voltage VCESAT ISW = 85mA; TA=25 °C 160 300 mV
Maximum Duty Cycle DMAX VFB = GND 90 %
Switch Current Limit Icl ILOAD = 0; TA=25 °C 300 500 700 mA
Switch Leakage Current ILKG VSW = 5V; VOUT = Open 0.01 5.0 μA
Shutdown Current ISHD VEN/SS = GND; VIN = 3V; VOUT = Open 3 5 μA
PWM Dimming Frequency(1) fDIM 1 10 kHz
EN/SS Threshold Low VIL 50 mV
EN/SS Threshold High VIH 1.8 V
Note:
1) Calculated from package in still air, mounted to 3”x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards.
2) Tested in accordance to JEDEC standard JESD22-A114B.
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
3
Electrical Characteristics (Cont.)
Parameter Symbol Conditions Min Typ Max Units
EN/SS Input Low Current IIL VEN/SS = GND 1.0 μA
EN/SS Input High Current IIH 60 100 μA
Output Over-Voltage Protection OVP 25 30 V
Schottky Forward Drop Vf_sch ID = 150mA 0.7 V
Schottky Leakage Current If_sch VOUT = 25V; VSW = GND 1.0 4.0 μA
Note:
1. Guaranteed by design.
Unless specifi ed: VIN = VEN/SS = 3.6V; CIN = 1μF; COUT = 0.22μF; L = 22μH; unless otherwise noted, TA = +25°C for Typ, -40ºC to 85°C for Min and Max.
© 2007 Semtech Corp.
SC4509
www.semtech.com
PRELIMINARY
POWER MANAGEMENT
4
Pin Confi guration Ordering Information
1
2
3
6
5
4
VOUT
GND
FB
SW
VIN
EN/SS
Part Numbers Package
SC4509SKTRT(1)(2) SOT23-6
SC4509WLTRT(1)(2) MLPD-W8 2mmx2mmx0.75mm
SC4509EVB(3) Evaluation Board
6-pin - SOT23
TOP VIEW
1
2
3
4
8
7
6
5
T
FB
GND
GND
VOUT VOUT
SW
VIN
EN/SS
8-pin - MLPD 2X2
Notes:
(1) Only available in tape and reel packaging. A reel contains 3000 devices.
(2) Lead-free package. This product is fully WEEE and RoHS compliant.
(3) Specify package preference when ordering.
Marking Information
TOP MARK
BP00
BOTTOM MARK
yyww
Marking for SOT23, 6 Lead Package:
yyww = Datecode (Example: 0652)
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
5
Pin Descriptions
SOT23 MLPD 2X2 Pin Name Function
1 4, 5 VOUT Cathode side of the Schottky output voltage. Connect a 0.22μF capacitor from this
pin to ground.
2 2,3 GND Ground connection
31 FB
Feedback input pin. Connect a resistor from this pin to GND to program the LED
current.
4 8 EN/SS
Enable pin. When connected to logic high, the converter is enabled. When con-
nected to logic low, the converter is disabled. The LED brightness can be controlled
by applying a PWM signal to this pin.
5 7 VIN Input voltage pin. Connect a 1μF capacitor from this pin to GND.
6 6 SW Switching pin - collector of the internal switch.
N/A T Exposed pad (bottom); connect to GND directly beneath package.
© 2007 Semtech Corp.
SC4509
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PRELIMINARY
POWER MANAGEMENT
6
Block Diagram
S
Ramp
Generator
1.2MHz
Oscillator
OVP
V
REF
1.25V
R
S
Q
FB
VIN
EN/SS GND
SW
PWM
VOUT
Internal Schottky
199mV
Theory of Operation
The SC4509 is a constant frequency PWM step-up regu-
lator IC designed to operate with an input voltage range
from 2.7V to 10V.
A maximum output voltage of 20V allows for up to fi ve LEDs
to be connected in series, providing even illumination by
passing the same output current through each LED.
Designed for a low 199mV, the feedback voltage has a
direct effect on the converter effi ciency. Because the volt-
age drop across the feedback resistor does not contribute
to the output power (LED brightness), the lower the feed-
back voltage, the higher the effi ciency. A 1.2MHz oscillator
frequency saves board space by reducing external compo-
nent sizes, making the SC4509 ideal for battery-operated
products.
The SC4509 can be confi gured as a voltage regulated
boost converter or as a current-regulating boost converter
for driving white LEDs. The device is designed to be stable
without additional external components in both cases.
Over-Voltage Protection (OVP)
To prevent the output voltage from exceeding the maxi-
mum switch voltage rating (30V), an over-voltage protec-
tion circuit is integrated. As soon as the output voltage
exceeds the OVP threshold, the converter stops switching
and the output voltage starts to drop. When the output
voltage drops back below the OVP threshold, the convert-
er resumes operation. This sequence will repeat for as
long as is necessary.
Enable and PWM Dimming
The SC4509 provides the EN/SS pin to serve multiple
functions. Its main function is as an enable pin (active
high). It also can be used to control LED brightness
when a PWM signal (up to 10kHz) of varying duty cycle is
applied. A third function acts as a soft-start control. Soft
start can be implemented by ramping the voltage applied
to the pin at startup or by slowly increasing the PMW duty
cycle.
∑
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
7
Applications Information
Programming the LED Current
Please refer to the Typical Application Circuit on page 1.
The LED current is programmed by connecting a resistor
(R1) between the FB pin and GND. The LED current in
mA is given by the following equation:
I
LED = 199/R1
where R1 value is in Ohms.
Setting the Output Voltage
The non-inverting input of the internal error amplifi er is
tied to a 199mV voltage reference. A simple voltage divider
(R1 at the top and R2 at the bottom) sets the converter
output voltage. Please refer to the Application Circuit for
OLED Panels on the next page. The voltage feedback gain
h = 0.199/Vo is related to the divider resistors value as
R2R1
R2
h
Once either R1 or R2 is chosen, the other can be calcu-
lated for the desired output voltage Vo. Since the number
of standard resistance values is limited, the calculated
resistance may not be available as a standard value resis-
tor. As a result, there will be a set error in the converter
output voltage. This non-random error is caused by the
feedback voltage divider ratio. It cannot be corrected by
the feedback loop.
© 2007 Semtech Corp.
SC4509
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PRELIMINARY
POWER MANAGEMENT
8
Application Circuit for OLED Panels
L1
22μH
R2
SW
6
VIN
5
EN/SS
4
GND
2
FB 3
VOUT
1
U2
SC4509
Vo
R1
C2
1μF
VIN
C1
1μF
EN/SS
OLED
PANEL
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
9
Effi ciency vs. LED Current
VIN = 2.7V, VOUT = 16V, (4 LED)
Effi ciency vs. LED Current
VIN = 3.3V, VOUT = 16V, (4 LED)
Effi ciency vs. LED Current
VIN = 3.6V, VOUT = 16V, (4 LED)
ILED (mA)
ILED (mA)
ILED (mA)
Effi ciency (%)
Effi ciency (%)
Effi ciency (%)
30%
35%
40%
45%
50%
55%
60%
65%
70%
75%
80%
0 2 4 6 8 10121416182022
30%
35%
40%
45%
50%
55%
60%
65%
70%
75%
80%
85%
0 2 4 6 8 10121416182022 242628 3032
35%
40%
45%
50%
55%
60%
65%
70%
75%
80%
85%
0 2 4 6 8 101214161820222426283032
Effi ciency vs. LED Current vs. Input Voltage
VOUT = 12V, (3 LED)
35%
40%
45%
50%
55%
60%
65%
70%
75%
80%
85%
0 5 10 15 20 25 30 35
VIN = 3.6V
VIN = 2.7V
ILED (mA)
Effi ciency (%)
Feedback Voltage vs. Temperature vs. LED Current,
VOUT = 16V
ILED = 20mA
ILED = 30mA
197.0
198.0
199.0
200.0
201.0
202.0
203.0
-40 -20 0 20 40 60 80 100
Frequency vs. Temperature vs. Input Voltage,
VOUT = 16V
VIN = 3.6V
VIN = 2.7V
VIN = 3.3V
1.00
1.05
1.10
1.15
1.20
-40-200 20406080
FBK (mV)
Temperature (Deg. C) Temperature (Deg. C)
Frequency (MHz)
Typical Characteristics
© 2007 Semtech Corp.
SC4509
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PRELIMINARY
POWER MANAGEMENT
10
40°C 25°C
85°C
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0.00.40.81.21.62.02.42.83.23.64.0
40°C
25°C
85°C
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
55.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
Output Voltage vs. EN/SS Voltage vs. Temperature,
VIN = 3.6V; VOUT = 16V
EN/SS Input Current vs. EN/SS Voltage vs. Temperature,
VIN = 3.6V; VOUT = 16V
VEN/SS (Volts)
VEN/SS (Volts)
IEN/SS (μA)
VOUT (V)
LED Current vs. PWM Dimming Duty Cycle
VIN = 3.6V; VOUT = 16V; FPWM = 1kHz
LED Current vs. PWM Dimming Duty Cycle
VIN = 3.6V; VOUT = 16V; FPWM = 10kHz
DTY (%)
6
8
10
12
14
16
18
20
22
15 25 35 45 55 65 75 85 95
0
2
4
6
8
10
12
14
16
18
20
22
0 102030405060708090100
Switch Current Limit vs. Complementary
Duty Cycle (1-D) vs. Temperature
(1-D) (%)
Switch Current Limit vs. Temperature vs.
Complementary Duty Cycle (1-D)
Temperature (Deg. C)
DTY (%)
Current Limit (mA)
ILED (mA)
ILED (mA)
Typical Characteristics (Cont.)
100
200
300
400
500
600
700
800
0 102030405060708090100
85°C
25°C
0°C
-40°C
200
250
300
350
400
450
500
550
600
650
700
-40 -20 0 20 40 60 80 100
60%
40%
20%
90%
10%
Current Limit (mA)
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
11
Switch Complementary Duty Cycle vs.
Input Voltage vs. LED Current, VOUT = 16V, (4 LED)
VIN (V)
0.0%
5.0%
10.0%
15.0%
20.0%
25.0%
30.0%
35.0%
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3
ILED = 30mA
ILED = 20mA
(1-D) (%)
Typical Characteristics (Cont.)
Switching Waveform
VIN = 3.6V; ILED = 20mA; VOUT = 16V (4 LEDs)
Startup Current
VIN = 3.6V; ILED = 30mA; VOUT = 16V (4 LEDs)
© 2007 Semtech Corp.
SC4509
www.semtech.com
PRELIMINARY
POWER MANAGEMENT
12
Layout Example
Top Layer
Bottom Layer
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
13
DIMENSIONS
INCHES
Y
Z
DIM
G
P
X
C
MILLIMETERS
P
(C) Z
Y
G
.043
.141
.055
(.098)
.037
.024
1.40
(2.50)
0.95
0.60
1.10
3.60
XDIMENSIONS
INCHES
Y
Z
DIM
G
P
X
C
MILLIMETERS
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
NOTES:
1.
.110 BSC
.037 BSC
DETAIL
aaa C
SEATING
ccc C
2X N/2 TIPS
2X E/2
6
SEE DETAIL
A1
A
A2
bxN
A
.008
12
N
E
.060
.114
.063
.122
.010 -
6
A
0.20
1.60
3.10
2.80 BSC
0.95 BSC
.069 1.50
2.90
.020 0.25
1.75
0.50
-
EI
L
(L1)
c
01
0.25
PLANE
GAGE
H
2.80.110
bbb C A-B D
0°
.008
-
.004
.012
.003
(.024)
.018
-
.035
.000
.035
-
-
.045
0.10
0.20
10° 0° -10°
1.15
(0.60)
0.45.024
.009
0.30
0.08
.057
.051
.006 0.00
.90
0.90
0.22
0.60
-
0.15
1.45
1.30
-
-
1.90 BSC.075 BSC
A
e1 D
e
B
C
PLANE
D
DATUMS AND TO BE DETERMINED AT DATUM PLANE
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
3.
OR GATE BURRS.
NOTES:
1.
2. -A- -B- -H-
SIDE VIEW
NOM
INCHES
DIMENSIONS
L1
aaa
bbb
ccc
01
N
DIM
c
e
e1
L
E1
E
D
A1
A2
b
A
MIN
MILLIMETERS
MAX MIN NOM MAX
Land Pattern - SOT23-6
Outline Drawing - SOT23-6
© 2007 Semtech Corp.
SC4509
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PRELIMINARY
POWER MANAGEMENT
14
Outline Drawing - MLPD-W8 2x2
2.00
.079
PIN 1
INDICATOR
(LASER MARK)
A1
SEATING
PLANE
C
B
A
aaa C
1
N
E
2.10
2.10
1.90
1.90
.083
.083
.075
.075
A
2
INCHES
.020 BSC
b.007
bbb
aaa
N
L
e
D
.008
DIM
A1
A2
MIN
.000
.028
0.30
0.18.012 0.25
.010
0.400.20
.003
.003
8
.012
.079
.016
0.08
0.08
8
0.30
2.00
0.50 BSC
MILLIMETERS
MAX
0.05
0.80
DIMENSIONS
MIN
0.00
NOM
(.008)
.030
.001
MAX
.002
.031
NOM
0.70
0.02
(0.20)
0.75
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
NOTES:
1.
A2
D
e/2
e
bxN
bbb C A B
COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.
2.
D1 .059 .063 .067 1.50 1.60 1.70
E1 .031 .035 .039 0.80 0.90 1.00
D/2
E/2
E
LxN
E1
D1
A
Land Pattern - MLPD-W8 2x2
X
G
Y
R
P
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
INCHES
DIMENSIONS
P
Z
X
Y
C
G
DIM MILLIMETERS
FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR
FUNCTIONAL PERFORMANCE OF THE DEVICE.
SHALL BE CONNECTED TO A SYSTEM GROUND PLANE.
THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD
3.
H.063 1.60
K.035 0.90
R.006 0.15
KZ
(C)
H
.028
.106
(.079)
.051
0.70
2.70
(2.00)
1.30
0.30
0.50.020
.012
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
NOTES:
2.
© 2007 Semtech Corp. www.semtech.com
SC4509
POWER MANAGEMENT
15
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 Fax: (805) 498-3804
Contact Information
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