High Efficiency Integrated Driver for

4-Strings of 150mA LEDs

SC441A

POWER MANAGEMENT

January 18, 2010

1

www.semtech.com

Features

Applications

Description

„

Wide input voltage range from 4.5V to 21V

„

36V maximum output voltage

„

Drives up to 40 WLEDs in 4 strings

„

Programmable LED current for up to 150mA per

string

„

+/- 2% string-to-string current matching

„

Up to 90% efficiency

„

Wide 0.2% to 100% PWM dimming range

„

Possible analog dimming

„

Integrated 3.0A power switch

„

700KHz switching frequency for small size

„

Adjustable OVP for cost-effective output cap selection

„

Open/short LED protection

„

Thermal protection with auto-recovery

„

Thermally enhanced TSSOP-20 EDP package

„

Fully WEEE and RoHS compliant

„

AEC-Q100 Grade 3 qualified

„

Medium-sized LCD panel

„

Notebook Display

„

Automotive Car Navigation Display

„

Sub-Notebook and Tablet Computer Displays

„

Portable Media Players

The SC441A is a high-efficiency multiple string WLED driv-

er with an integrated boost converter. It operates over a

wide input range from 4.5V to 21V with a maximum out-

put voltage of 36V and a 3.0A internal power switch. It

can drive up to forty WLEDs in 4 strings with current up

to 150mA per string. The string-to-string current match-

ing is 2% typical, 3% maximum. 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 700KHz switching frequency enables the user to op-

timize the external component sizes for efficiency. When

there are fewer than 10 LEDs in each string, users can ad-

just the output voltage protection yielding an allowable

reduction in associated costs, size and voltage ratings of

the output capacitor.

The SC441A also features comprehensive open and short-

circuit LED protection functions. It disables the corre-

sponding strings with LED open or LED short conditions

while maintaining normal operation of other, unaffected

LED strings. This feature allows LCD panels to remain view-

able even under LED failure, wire disconnect, or short-cir-

cuit conditions. The internal thermal shutdown protects

the IC from overheating at abnormal conditions.

The SC441A is available in a thermally-enhanced TSSOP-

20 EDP package.

Typical Application Circuit

1

4

VOUT

SS

PGND

IOSET

IO1-4

COMP

OVPIN

AGND

VIN

SW

PWM

EN

OVPRTN

SW

FFLAG

PGND

IOGND

SC441A

4 Strings

1

10

Vin (4.5V -21V)

2

EDP

PGND

IOSET

IO1- 4

COMP

SS

AGND

VOUT

OVPIN