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POWER MANAGEMENT POWER MANAGEMENT Description
SC4509 Highly Integrated Step-Up Converter for White LED Applications in MLPD-W8-2x2
Features
VIN range: 2.7V -- 10V Integrated Schottky diode 81% efficiency 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 converter targeted for white LED backlighting applications. It is designed to drive up to five 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 efficiency, 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 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.
Applications
Digital Video Cameras White LED Backlight Driver OLED Display Driver Portable Media Players GPS Receivers Cellular Phones PDAs and Handheld Computers
Typical Application Circuit
Vin
L1
Vo
22H
LED1
LED2
C2 0.22F LED3 U2 5 VIN
6 VOUT SW 1
EN/SS
4 C1 1F EN/SS
SC4509
GND
LED4 FB 3 R1
March 26, 2007
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SC4509
POWER MANAGEMENT Absolute Maximum Rating PRELIMINARY
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability.
Parameter
Input Supply Voltage SW Voltage Maximum Output Voltage Feedback Voltage EN/SS Voltage Maximum Junction Temperature Storage Temperature Range Thermal Impedance Junction to Ambient(1) MLPD-W8 SOT23-6
Symbol
VIN VSW VOUT VFB VEN/SS TJ TSTG JA TLEAD TPKG VESD
Maximum
-0.3 to 20 -0.3 to 30 30 -0.3 to 20 -0.3 to VIN + 0.3 125 -65 to +150 78 165 300 260 2
Units
V V V V V C C C/W C C kV
Lead Temperature (Soldering), 10s (SOT23-6 package only) Peak IR Flow Temperature, (10-40sec) ESD Rating (Human Body Model)(2)
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.
Electrical Characteristics
Unless specified: VIN = VEN/SS = 3.6V; CIN = 1F; COUT = 0.22F; L = 22H; unless otherwise noted, TA = +25C for Typ, -40C to 85C for Min and Max.
Parameter
Input Voltage Quiescent Current Feedback Voltage Feedback Pin Bias Current Switching Frequency Maximum Output Voltage Switch Saturation Voltage Maximum Duty Cycle Switch Current Limit Switch Leakage Current Shutdown Current PWM Dimming Frequency(1) EN/SS Threshold Low EN/SS Threshold High
Symbol
VIN IQ VFB IQFB fOSC VOUT VCESAT DMAX Icl ILKG ISHD fDIM VIL VIH
Conditions
Min
2.7
Typ
Max
10
Units
V mA mV nA MHz V
No switching 182
2.6 199 35
3.3 216 100 1.4
TA=25 C
1.0 20
1.2
ISW = 85mA; TA=25 C VFB = GND ILOAD = 0; TA=25 C VSW = 5V; VOUT = Open VEN/SS = GND; VIN = 3V; VOUT = Open 90 300
160
300
mV %
500 0.01 3 1
700 5.0 5 10 50
mA A A kHz mV V
1.8
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SC4509
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless specified: VIN = VEN/SS = 3.6V; CIN = 1F; COUT = 0.22F; L = 22H; unless otherwise noted, TA = +25C for Typ, -40C to 85C for Min and Max.
Parameter
EN/SS Input Low Current EN/SS Input High Current Output Over-Voltage Protection Schottky Forward Drop Schottky Leakage Current
Note: 1. Guaranteed by design.
Symbol
IIL IIH OVP Vf_sch If_sch
Conditions
VEN/SS = GND
Min
Typ
Max
1.0
Units
A A V V
60 25 ID = 150mA VOUT = 25V; VSW = GND 30 0.7 1.0
100
4.0
A
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SC4509
POWER MANAGEMENT Pin Configuration
VOUT GND FB
PRELIMINARY Ordering Information
Part Numbers Package SOT23-6 MLPD-W8 2mmx2mmx0.75mm Evaluation Board
1 2 3
6 5 4
SW
SC4509SKTRT(1)(2)
VIN
SC4509WLTRT(1)(2)
EN/SS
SC4509EVB(3)
6-pin - SOT23
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.
FB GND GND VOUT
1 2 3 4 T
8
EN/SS VIN SW VOUT
TOP VIEW
7 6 5
8-pin - MLPD 2X2
Marking Information
TOP MARK
BP00
BOTTOM MARK
yyww
Marking for SOT23, 6 Lead Package: yyww = Datecode (Example: 0652)
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SC4509
POWER MANAGEMENT Pin Descriptions
SOT23
1 2 3
MLPD 2X2
4, 5 2,3 1
Pin Name
VOUT GND FB
Function
Cathode side of the Schottky output voltage. Connect a 0.22F capacitor from this pin to ground. Ground connection 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. Input voltage pin. Connect a 1F capacitor from this pin to GND. Switching pin - collector of the internal switch. Exposed pad (bottom); connect to GND directly beneath package.
4
8
EN/SS
5 6 N/A
7 6 T
VIN SW
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SC4509
POWER MANAGEMENT Block Diagram PRELIMINARY
SW
Internal Schottky
FB VIN
VREF
1.25V 199mV
VOUT
PWM R S Q
OVP
S
EN/SS
Ramp Generator 1.2MHz Oscillator
GND
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 five 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 efficiency. Because the voltage drop across the feedback resistor does not contribute to the output power (LED brightness), the lower the feedback voltage, the higher the efficiency. 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 configured 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.
(c) 2007 Semtech Corp.
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.
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SC4509
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: ILED = 199/R1 where R1 value is in Ohms. Setting the Output Voltage The non-inverting input of the internal error amplifier 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
h R2 R1 R2
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.
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SC4509
POWER MANAGEMENT Application Circuit for OLED Panels PRELIMINARY
L1
VIN
22H U2 5 VIN R1
Vo
OLED PANEL
6
SC4509
VOUT
SW
1
EN/SS
C1 1F
GND
4
EN/SS
FB
3 R2
C2 1F
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SC4509
POWER MANAGEMENT Typical Characteristics
Efficiency vs. LED Current VIN = 2.7V, VOUT = 16V, (4 LED)
80% 75% 70% 65%
Efficiency vs. LED Current VIN = 3.3V, VOUT = 16V, (4 LED)
85% 80% 75% 70%
Efficiency (%)
60% 55% 50% 45% 40% 35% 30% 0 2 4 6 8 10 12 14 16 18 20 22
Efficiency (%)
65% 60% 55% 50% 45% 40% 35% 30% 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
ILED (mA)
ILED (mA)
Efficiency vs. LED Current VIN = 3.6V, VOUT = 16V, (4 LED)
85% 80% 75% 70% 65%
Efficiency vs. LED Current vs. Input Voltage VOUT = 12V, (3 LED)
85% 80% 75% 70% 65%
VIN = 2.7V VIN = 3.6V
Efficiency (%)
60% 55% 50% 45% 40% 35% 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Efficiency (%)
60% 55% 50% 45% 40% 35% 0 5 10 15 20 25 30 35
ILED (mA)
ILED (mA)
203.0
Feedback Voltage vs. Temperature vs. LED Current, VOUT = 16V
1.20
Frequency vs. Temperature vs. Input Voltage, VOUT = 16V
VIN = 2.7V
202.0
1.15
201.0
ILED = 20mA ILED = 30mA
Frequency (MHz)
FBK (mV)
VIN = 3.3V
1.10
200.0
VIN = 3.6V
199.0
1.05
198.0
197.0 -40 -20 0 20 40 60 80 100
1.00 -40 -20 0 20 40 60 80
Temperature (Deg. C)
Temperature (Deg. C)
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SC4509
POWER MANAGEMENT Typical Characteristics (Cont.)
EN/SS Input Current vs. EN/SS Voltage vs. Temperature, VIN = 3.6V; VOUT = 16V
55.0 50.0 45.0 40.0 35.0
16.0
PRELIMINARY
Output Voltage vs. EN/SS Voltage vs. Temperature, VIN = 3.6V; VOUT = 16V
14.0
40C
25C
25C
12.0
IEN/SS (A)
30.0 25.0 20.0 15.0 10.0 5.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
VOUT (V)
10.0
40C
85C
8.0
6.0
85C
4.0
2.0 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
VEN/SS (Volts)
VEN/SS (Volts)
LED Current vs. PWM Dimming Duty Cycle VIN = 3.6V; VOUT = 16V; FPWM = 10kHz
22
22 20 18
LED Current vs. PWM Dimming Duty Cycle VIN = 3.6V; VOUT = 16V; FPWM = 1kHz
20
18
16 14
16
ILED (mA)
14
ILED (mA)
12 10 8 6 4
12
10
8
2 0
6 15 25 35 45 55 65 75 85 95
0
10
20
30
40
50
60
70
80
90
100
DTY (%)
DTY (%)
800
Switch Current Limit vs. Complementary Duty Cycle (1-D) vs. Temperature
-40C
700 650
Switch Current Limit vs. Temperature vs. Complementary Duty Cycle (1-D)
10%
700
600
20%
Current Limit (mA)
600
550
Current Limit (mA)
500
500 450 400 350
0C
400
60% 90% 40%
25C
300
85C
200
300 250
100 0 10 20 30 40 50 60 70 80 90 100
200 -40 -20 0 20 40 60 80 100
(1-D) (%)
Temperature (Deg. C)
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SC4509
POWER MANAGEMENT Typical Characteristics (Cont.)
Switch Complementary Duty Cycle vs. Input Voltage vs. LED Current, VOUT = 16V, (4 LED)
35.0%
Startup Current VIN = 3.6V; ILED = 30mA; VOUT = 16V (4 LEDs)
30.0%
25.0%
ILED = 20mA
20.0%
(1-D) (%)
ILED = 30mA
15.0%
10.0%
5.0%
0.0% 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
VIN (V)
Switching Waveform VIN = 3.6V; ILED = 20mA; VOUT = 16V (4 LEDs)
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SC4509
POWER MANAGEMENT Layout Example PRELIMINARY
Top Layer
Bottom Layer
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SC4509
POWER MANAGEMENT Outline Drawing - SOT23-6
DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX
.057 .035 .000 .006 .035 .045 .051 .010 .020 .003 .009 .110 .114 .122 .060 .063 .069 .110 BSC .037 BSC .075 BSC .012 .018 .024 (.024) 6 0 10 .004 .008 .008 0.90 0.00 .90 0.25 0.08 2.80 1.50 1.45 0.15 1.15 1.30 0.50 0.22 2.90 3.10 1.60 1.75 2.80 BSC 0.95 BSC 1.90 BSC 0.30 0.45 0.60 (0.60) 6 0 10 0.10 0.20 0.20
A e1 N EI 1 ccc C 2X N/2 TIPS B 2 E D
DIM
A A1 A2 b c D E1 E e e1 L L1 N 01 aaa bbb ccc
2X E/2
e
D aaa C A2 SEATING PLANE C A1 bxN bbb C A-B D A
H GAGE PLANE 0.25 L (L1) SEE DETAIL A DETAIL c
01
A
SIDE VIEW
NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS -AAND -BTO BE DETERMINED AT DATUM PLANE -H-
3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
Land Pattern - SOT23-6
X
DIM
(C) G Y P Z C G P X Y Z
DIMENSIONS MILLIMETERS INCHES
(.098) .055 .037 .024 .043 .141 (2.50) 1.40 0.95 0.60 1.10 3.60
NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET.
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SC4509
POWER MANAGEMENT Outline Drawing - MLPD-W8 2x2
B
PRELIMINARY
A
D
DIM
PIN 1 INDICATOR (LASER MARK) E
A aaa C A1 A2 C
SEATING PLANE
A A1 A2 b D D1 E E1 e L N aaa bbb
.028 .030 .031 .000 .001 .002 (.008) .007 .010 .012 .075 .079 .083 .059 .063 .067 .075 .079 .083 .031 .035 .039 .020 BSC .008 .012 .016 8 .003 .003
DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX
0.70 0.75 0.80 0.00 0.02 0.05 (0.20) 0.18 0.25 0.30 1.90 2.00 2.10 1.50 1.60 1.70 1.90 2.00 2.10 0.80 0.90 1.00 0.50 BSC 0.20 0.30 0.40 8 0.08 0.08
D1 1 E/2 LxN E1 2
N e e/2 D/2 bxN bbb CAB
NOTES:
1. 2. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.
Land Pattern - MLPD-W8 2x2
H R
DIM
Z
C G H K P R X Y Z
DIMENSIONS INCHES MILLIMETERS
(.079) .051 .063 .035 .020 .006 .012 .028 .106 (2.00) 1.30 1.60 0.90 0.50 0.15 0.30 0.70 2.70
(C) K
G
Y X P
NOTES: 1. 2. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 3. 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.
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SC4509
POWER MANAGEMENT
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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