High Efficiency Integrated Driver for

4-Strings of 150mA LEDs

SC441A

POWER MANAGEMENT

July 23, 2009



www.semtech.com

Features

Applications

Description

Wide input voltage range from 4.5V to 2V

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 00% PWM dimming range

Possible analog dimming

Integrated 2.5A 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

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Medium-sized LCD panel

Notebook Display

Automotive Car Navigation Display

Sub-Notebook and Tablet Computer Displays

Portable Media Players

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The SC44A 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 2V with a maximum out-

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

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

to 50mA 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: .

The 700KHz switching frequency enables the user to op-

timize the external component sizes for efficiency. When

there are fewer than 0 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 SC44A 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 SC44A 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