March 26, 2010

POWER MANAGEMENT

1

10-Channel, Integrated, High Efficiency

120 White LED Driver

SC442

Typical Application Circuit

Features

Wide input voltage range from 4.5V to 21V

42V maximum operating output voltage

Programmable LED current up to 30mA per string

+/- 1% current matching

Integrated 3A switch

Low current sink voltage

Up to 91% efficiency

Flexible LED configurations

Mismatched LED channels

Disable individual channel(s)

Parallel channels for high LED current

PWM dimming capability

Up to 50kHz dimming frequency

>500:1 dimming range

Switching frequency: 500kHz - 1MHz

Parallel device operation with Sync Pin

Protection features:

Adjustable OVP

Cycle-by-cycle current limit

LED short channel with disable /Open channnel

Over-Temperature protection

MLPQ-28 lead-free package (WEEE and RoHS compliant),

4×4mm × 0.6mm

Applications

Automotive LCD Backlighting

Desktop monitors

Notebook PCs

Portable TVs



































Description

The SC442 is a 10-channel, high efficiency integrated step-up

(boost) driver IC capable of powering up to 120 WLEDs. The device

has a wide input voltage of 4.5V to 21V with no internal regulator

or bypass capacitor required. The wide input range, up to 42V

output voltage and flexible implementation make it the ideal LED

backlight driver solution for medium to large LCD displays. The

current sink channels are programmed with an external resistor

up to 30mA each.

Channel-channel current matching is +/-1% . The device disables

open or shorted LEDs by disabling only the affected LED channel;

thus increasing LCD panel life. Channel-channel LED mismatch

voltage is accomodated by adjusting the SCPSET resistor. The

current sink channels may be operated in parallel for increased

LED current. Unused channels are be disabled by connecting the

pin to the input voltage.

Losses in the switching device and current sinks are minimized

across the operating range; yielding >90% efficiency and excel-

lent battery life for portable systems.

The device accepts PWM dimming up to 50kHz. Maximum dim-

ming range is greater than 500:1 with excellent linearity for opti-

mum PWM dimming characteristics. The high frequency dimming

capability (>20kHz) eliminates audio emissions and allows small

ceramic output capacitors.

Switching frequency is programmable from 200kHz to 1MHz;

allowing efficiency versus L/C sizing tradeoffs across the input/

output voltage range. Alternatively, the SYNC pin allows the

designer to synchronize the switching frequency to an external

system clock and, if necessary, a parallel SC442 device - eliminating

potential system intermodulation and interference problems.

Over-temperature shutdown protects the IC from over-heating

under abnormal conditions. The device is available in a small

4mmx4mm MLPQ-28 pin package with 0.6mm maximum height

and is fully WEEE and RoHS compliant.

Enable

Dimming

VOUT

SS

PGND

FS

SCPSET

IO1- 10

OVFB

IOGND

PWM

AGND

VIN = 4.5V– 21V

EN

COMP

VIN

SW

SCPEN

SCPEN

AGND

IOSET

SW

SYNC

10

Up to 120WLEDs

VOUT = Up to 42V

6.8uH

1.47k 12nF

47nF