POWER MANAGEMENT
POWER MANAGEMENT
Description
SC4509
Highly Integrated Step-Up Converter for
White LED Applications in MLPD-W8-2x2
Features
V
IN
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 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 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 R
SET
), 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.
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
22μH
LED1
LED2
C2
0.22μF
LED3
U2
5
VIN
6
VOUT
SW
1
EN/SS
4
C1
1μF
EN/SS
SC4509
GND
LED4
FB
3
R1
March 26, 2007
2
1
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