POWER MANAGEMENT

April 20 2007

1

High Efficiency Integrated Driver

for 6-Strings of 30mA LEDs

SC440

Typical Application Circuit

Features

Wide input range 4.5V to 21V

36V maximum output voltage with adjustable OVP for

smaller output capacitor

Drives up to 60 WLEDs in 6 strings

Programmable WLED current for up to 30mA per

string

1% string-to-string current matching

2.5A integrated power switch

Up to 91% efficiency

0.2% to 100% PWM dimming

Analog dimming

800KHz switching frequency for small external com-

ponent

Open/short LED protection

Short LED protection disable

<1uA shut-down current

Thermal protection

4mm x 4mm x1mm MLPQ-24 package (WEEE & RoHS

compliant)

Applications

Medium-sized LCD panel

Notebook Display

White LED Power Supplies

Sub-Notebook and Tablet Computer Displays

Portable Media Players

LCD Monitors

Digital Video Cameras

Description

The SC440 is a high-efficiency multiple string WLED driver

with an integrated boost converter. It operates over a wide

input range from 4.5V to 21V with a maximum output

voltage of 36V and a 2.5A internal power switch.

It can drive up to 36V output voltage in 6 strings with

current up to 30mA per string. The string-to-string current

matching is 1% typical, 3% maximum and the overall

efficiency is greater than 90% due to the low current sense

voltage and a low-impedance internal power switch. The

wide PWM dimming range boasts a ratio of 500: 1.

The 800kHz switching frequency enables the user to

optimize the external component sizes for high efficiency.

When there are fewer LEDs in each string, users can use

a lower output voltage protection level which yields an

allowable reduction in associated costs, size and voltage

ratings of the output capacitor.

The SC440 also features a comprehensive open and

short circuit LED protection functions. It disables the

corresponding strings with LED open or LED short

conditions while keeping other strings under normal

operation. This feature

allows LCD panels to remain

viewable even under LED failure, wire disconnect, or short-

circuit conditions. The short LED protection function can

be disabled. The internal thermal shutdown protects the

IC from overheating at abnormal conditions. The SC440

is available in a common 4mm x 4mm x1mm MLPQ-24

package.

6

PGND

VIN

SW

PWM

EN

OVPRTN

SW

FFLAG

PGND

IOGND

6 Strings

10

SCP_EN

AGND

IOSET

IO1-6

VOUT

OVPIN

COMP

SS

EDP

SC440

1

Vin (4.5V - 21V)

2

-6