SC4509 Datasheet, PDF (1/15 Pages) Semtech Corporation – Highly Integrated Step-Up Converter for White LED Applications in MLPD-W8-2x2

SC4509
PPOOWWEERRMMAANNAAGGEEMMEENNTT
Highly Integrated Step-Up Converter for
White LED Applications in MLPD-W8-2x2
Description
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 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 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.
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
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
22μH
Vo
LED1
EN/SS
C1
1μF
U2
5 ^VIN
4 ^EN/SS
SC4509
FB ₃
LED2
LED3
C2
0.22μF
LED4
R1
March 26, 2007
1
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