Highly Integrated Step-Up Converter for
White LED Applications in MLPD-W8-2x2
POWER MANAGEMENT
POWER MANAGEMENT
Description Features
IN range: 2.7V — 10V
The SC4509 is a highly integrated step-up DC/DC converter 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 frequency. 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 R
), making it ideal for
SET
applications that require low cost and minimal PCB area.
The SC4509 offers current limit and over-voltage protection (OVP) to safeguard the device under extreme operating 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.
V
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
Applications
Digital Video Cameras
White LED Backlight Driver
OLED Display Driver
Portable Media Players
GPS Receivers
Cellular Phones
PDAs and Handheld Computers
SC4509
Typical Application Circuit
Vin
EN/SS
C1
1μF
L1
22μH
5
4
U2
VIN
EN/SS
6
SW
SC4509
Vo
LED1
LED2
C2
1
VOUT
FB
GND
2
3
LED3
LED4
R1
0.22μF
March 26, 2007
1
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SC4509
POWER MANAGEMENT
PRELIMINARY
Absolute Maximum Rating
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.
Parameter Symbol Maximum Units
Input Supply Voltage
SW Voltage V
Maximum Output Voltage V
Feedback Voltage V
EN/SS Voltage V
Maximum Junction Temperature T
Storage Temperature Range T
Thermal Impedance
Junction to Ambient
(1)
MLPD-W8
SOT23-6 165
Lead Temperature (Soldering), 10s (SOT23-6 package only) T
Peak IR Flow Temperature, (10-40sec) T
ESD Rating (Human Body Model)
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.
(2)
V
EN/SS
θ
V
IN
SW
OUT
FB
J
STG
JA
LEAD
PKG
ESD
-0.3 to 20 V
-0.3 to 30 V
30 V
-0.3 to 20 V
-0.3 to VIN + 0.3 V
125 °C
-65 to +150 °C
78
C/W
300 °C
260 °C
2kV
Electrical Characteristics
Unless specifi ed: VIN = V
Parameter Symbol Conditions Min Typ Max Units
Input Voltage V
Quiescent Current I
Feedback Voltage V
Feedback Pin Bias Current I
Switching Frequency f
Maximum Output Voltage V
Switch Saturation Voltage V
Maximum Duty Cycle D
Switch Current Limit I
Switch Leakage Current I
Shutdown Current I
PWM Dimming Frequency
EN/SS Threshold Low V
EN/SS Threshold High V
= 3.6V; C
EN/SS
= 1μF; C
IN
(1)
= 0.22μF; L = 22μH; unless otherwise noted, TA = +25°C for Typ, -40ºC to 85°C for Min and Max.
OUT
IN
Q
FB
QFB
OSC
OUT
CESAT
MAX
cl
LKG
SHD
f
DIM
IL
IH
No switching 2.6 3.3 mA
I
= 85mA; TA=25 °C 160 300 mV
SW
I
LOAD
VSW = 5V; V
V
= GND; VIN = 3V; V
EN/SS
TA=25 °C 1.0 1.2 1.4 MHz
V
= GND 90 %
FB
= 0; TA=25 °C 300 500 700 mA
= Open 0.01 5.0 μA
OUT
= Open 3 5 μA
OUT
1 10 kHz
2.7 10 V
182 199 216 mV
35 100 nA
20 V
50 mV
1.8 V
© 2007 Semtech Corp.
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SC4509
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specifi ed: V
Parameter Symbol Conditions Min Typ Max Units
IN
= V
= 3.6V; C
EN/SS
= 1μF; C
IN
= 0.22μF; L = 22μH; unless otherwise noted, TA = +25°C for Typ, -40ºC to 85°C for Min and Max.
OUT
EN/SS Input Low Current I
EN/SS Input High Current I
IL
IH
V
= GND 1.0 μA
EN/SS
60 100 μA
Output Over-Voltage Protection OVP 25 30 V
Schottky Forward Drop V
Schottky Leakage Current I
Note:
1. Guaranteed by design.
f_sch
f_sch
ID = 150mA 0.7 V
V
= 25V; VSW = GND 1.0 4.0 μA
OUT
© 2007 Semtech Corp. www.semtech.com
3
SC4509
POWER MANAGEMENT
Pin Confi guration
VOUT
GND
FB
1
2
3
6-pin - SOT23
1
FB
GND
GND
VOUT VOUT
2
3
4
TOP VIEW
6
5
4
T
SW
VIN
EN/SS
8
7
6
5
EN/SS
VIN
SW
PRELIMINARY
Ordering Information
Part Numbers Package
SC4509SKTRT
SC4509WLTRT
SC4509EVB
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.
(1)(2)
(1)(2)
(3)
MLPD-W8 2mmx2mmx0.75mm
SOT23-6
Evaluation Board
8-pin - MLPD 2X2
Marking Information
TOP MARK
BP00
BOTTOM MARK
yyww
Marking for SOT23, 6 Lead Package:
yyww = Datecode (Example: 0652)
© 2007 Semtech Corp.
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POWER MANAGEMENT
Pin Descriptions
SOT23 MLPD 2X2 Pin Name Function
SC4509
1 4, 5 VOUT
2 2,3 GND Ground connection
31 FB
4 8 EN/SS
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.
Cathode side of the Schottky output voltage. Connect a 0.22μF capacitor from this
pin to ground.
Feedback input pin. Connect a resistor from this pin to GND to program the LED
current.
Enable pin. When connected to logic high, the converter is enabled. When connected to logic low, the converter is disabled. The LED brightness can be controlled
by applying a PWM signal to this pin.
© 2007 Semtech Corp. www.semtech.com
5
SC4509
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
POWER MANAGEMENT
Block Diagram
PRELIMINARY
∑
Theory of Operation
The SC4509 is a constant frequency PWM step-up regulator 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 feedback voltage, the higher the effi ciency. A 1.2MHz oscillator
frequency saves board space by reducing external component 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 maximum switch voltage rating (30V), an over-voltage protection 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 converter 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.
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POWER MANAGEMENT
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:
SC4509
I
= 199/R1
LED
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
R2
h
R2R1
Once either R1 or R2 is chosen, the other can be calculated 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 resistor. 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. www.semtech.com
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SC4509
POWER MANAGEMENT
Application Circuit for OLED Panels
L1
VIN
22μH
5
EN/SS
C1
1μF
4
U2
VIN
EN/SS
6
SW
SC4509
2
GND
PRELIMINARY
Vo
OLED
1
VOUT
3
FB
R1
R2
PANEL
C2
1μF
© 2007 Semtech Corp.
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POWER MANAGEMENT
Typical Characteristics
SC4509
Effi ciency vs. LED Current
80%
VIN = 2.7V, V
75%
70%
65%
60%
55%
50%
Effi ciency (%)
45%
40%
35%
30%
0 2 4 6 8 10121416182022
I
= 16V, (4 LED)
OUT
(mA)
LED
Effi ciency vs. LED Current
85%
V
80%
75%
70%
65%
60%
55%
50%
Effi ciency (%)
45%
40%
35%
0 2 4 6 8 101214161820222426283032
= 3.6V, V
IN
I
= 16V, (4 LED)
OUT
(mA)
LED
Effi ciency vs. LED Current
V
= 3.3V, V
85%
80%
75%
70%
65%
60%
55%
Effi ciency (%)
50%
45%
40%
35%
30%
0 2 4 6 8 10121416182022 242628 3032
IN
= 16V, (4 LED)
OUT
I
LED
(mA)
Effi ciency vs. LED Current vs. Input Voltage
Effi ciency (%)
V
85%
80%
75%
70%
65%
60%
55%
50%
45%
40%
35%
0 5 10 15 20 25 30 35
= 12V, (3 LED)
OUT
VIN = 2.7V
I
LED
(mA)
VIN = 3.6V
Feedback Voltage vs. Temperature vs. LED Current,
V
= 16V
203.0
202.0
201.0
200.0
FBK (mV)
199.0
198.0
197.0
ILED = 20mA
-40 -20 0 20 40 60 80 100
Temperature (Deg. C)
© 2007 Semtech Corp. www.semtech.com
OUT
ILED = 30mA
Frequency (MHz)
9
Frequency vs. Temperature vs. Input Voltage,
V
= 16V
1.20
1.15
1.10
1.05
1.00
-40-20 0 20406080
Temperature (Deg. C)
OUT
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
SC4509
POWER MANAGEMENT
Typical Characteristics (Cont.)
EN/SS Input Current vs. EN/SS Voltage vs. Temperature,
VIN = 3.6V; V
55.0
50.0
45.0
40.0
35.0
30.0
(μA)
I
EN/SS
25.0
20.0
15.0
10.0
5.0
0.0
40°C
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
25°C
VEN/SS (Volts)
LED Current vs. PWM Dimming Duty Cycle
22
VIN = 3.6V; V
20
18
16
14
(mA)
LED
I
12
10
8
6
15 25 35 45 55 65 75 85 95
OUT
= 16V
OUT
85°C
= 16V; FPWM = 10kHz
DTY (%)
PRELIMINARY
Output Voltage vs. EN/SS Voltage vs. Temperature,
VIN = 3.6V; V
16.0
14.0
40°C
12.0
10.0
VOUT (V)
8.0
6.0
4.0
2.0
0.00.40.81.21.62.02.42.83.23.64.0
25°C
85°C
VEN/SS (Volts)
LED Current vs. PWM Dimming Duty Cycle
VIN = 3.6V; V
22
20
18
16
14
12
10
(mA)
LED
I
8
6
4
2
0
0 102030405060708090100
OUT
= 16V
OUT
= 16V; FPWM = 1kHz
DTY (%)
Switch Current Limit vs. Complementary
800
700
600
500
400
Current Limit (mA)
300
200
100
0 10203040 5060708090100
Duty Cycle (1-D) vs. Temperature
-40°C
0°C
25°C
85°C
(1-D) (%)
© 2007 Semtech Corp.
700
650
600
550
500
450
400
Current Limit (mA)
350
300
250
200
10
Switch Current Limit vs. Temperature vs.
Complementary Duty Cycle (1-D)
10%
60%
90%
40%
-40 -20 0 20 40 60 80 100
Temperature (Deg. C)
20%
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POWER MANAGEMENT
Typical Characteristics (Cont.)
SC4509
Switch Complementary Duty Cycle vs.
Input Voltage vs. LED Current, V
35.0%
30.0%
25.0%
20.0%
15.0%
(1-D) (%)
10.0%
5.0%
0.0%
ILED = 20mA
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
VIN (V)
= 16V, (4 LED)
OUT
ILED = 30mA
Switching Waveform
VIN = 3.6V; I
= 20mA; V
LED
= 16V (4 LEDs)
OUT
V
= 3.6V; I
IN
Startup Current
= 30mA; V
LED
= 16V (4 LEDs)
OUT
© 2007 Semtech Corp. www.semtech.com
11
SC4509
POWER MANAGEMENT
Layout Example
PRELIMINARY
Top Layer
Bottom Layer
© 2007 Semtech Corp.
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POWER MANAGEMENT
Outline Drawing - SOT23-6
SEATING
PLANE
2X
E/2
ccc C
2X N/2 TIPS
aaa
C
C
A
N
12
B
D
SIDE VIEW
e1
D
E
EI
e
A
A2
A1
bxN
bbb C A-B D
SEE DETAIL
DIM
A
A1
A2
b
c
D
E1
E
e
e1
L
L1
N
01
aaa
bbb
ccc
GAGE
PLANE
0.25
A
MIN
.035
.000
.035
.010
.003
.060
.012
0°
H
INCHES
.110 BSC
.037 BSC
DIMENSIONS
MILLIMETERS
NOM
MAX MIN NOM MAX
-
.057
.006 0.00
.051
.020 0.25
.009
.122
.069 1.50
10° 0°
DETAIL
0.90
.90
0.08
2.80.110
0.30
(L1)
A
-
.045
-
.114
.063
.018
(.024)
6
.004
.008
.008
1.15
2.90
1.60
2.80 BSC
0.95 BSC
1.90 BSC.075 BSC
0.45.024
(0.60)
0.10
0.20
0.20
L
SC4509
-
1.45
-
0.15
1.30
-
0.50
-
0.22
3.10
1.75
0.60
6
-
10°
c
01
NOTES:
1.
2. -A- -B- -H-
3.
Land Pattern - SOT23-6
X
(C)
P
NOTES:
1.
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
DATUMS AND TO BE DETERMINED AT DATUM PLANE
DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
OR GATE BURRS.
DIMENSIONS
DIMENSIONS
DIM
DIM
G
Z
Y
INCHES
INCHES
C
C
G
G
P
P
X
X
Y
Y
Z
Z
(.098)
.055
.037
.024
.043
.141
MILLIMETERS
MILLIMETERS
(2.50)
1.40
0.95
0.60
1.10
3.60
© 2007 Semtech Corp. www.semtech.com
13
SC4509
POWER MANAGEMENT
Outline Drawing - MLPD-W8 2x2
A
PIN 1
INDICATOR
(LASER MARK)
aaa
C
A1
LxN
E/2
e
PRELIMINARY
e/2
B
DIMENSIONS
INCHES
DIM
MIN
E
A
SEATING
PLANE
A2
C
E1
bxN
bbb C A B
A1
A2
D1
E1 .031 .035 .039
aaa
bbb
NOM
.028
A
.000
(.008)
b
.007
D
.075
.059 .063 .067
E
.075
e
.020 BSC
L
.008
N
.030
.001
.010
.079
.079
.012
8
.003
.003
MILLIMETERS
MAX
MIN
0.70
.031
0.00
.002
0.18.012
1.90
.083
1.50 1.60 1.70
1.90
.083
0.80 0.90 1.00
.016
NOM
0.75
0.02
(0.20)
0.25
2.00
2.00
0.50 BSC
0.30
8
0.08
0.08
MAX
0.80
0.05
0.30
2.10
2.10
0.400.20
D
D1
1
2
N
D/2
NOTES:
1.
2.
Land Pattern - MLPD-W8 2x2
(C)
NOTES:
1.
2.
3.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.
R
H
DIM MILLIMETERS
C
G
Z
K
X
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
THIS LAND PATTERN IS FOR REFERE NCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD
SHALL BE CONNECTED TO A SYSTEM GROUND PLANE.
FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR
FUNCTIONAL PERFORMANCE OF THE DEVICE.
G
Y
P
H
K.035 0.90
P
R
X
Y
Z
DIMENSIONS
INCHES
(.079)
.051
.063 1.60
.006 0.15
.012
.028
.106
(2.00)
1.30
0.50.020
0.30
0.70
2.70
© 2007 Semtech Corp.
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POWER MANAGEMENT
SC4509
Contact Information
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 Fax: (805) 498-3804
www.semtech.com
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