High E ciency Integrated Driver for

3-Strings of 100mA LEDs

SC446

POWER MANAGEMENT

January 28, 2010

1

www.semtech.com

Features

Applications

Description

„

Wide input voltage range from 4.5V to 27V

„

36V maximum output voltage

„

Drives up to 30 WLEDs in 3 strings

„

Programmable LED current for up to 100mA per

string

„

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

„

Up to 90% eciency

„

Wide 0.2% to 100% PWM dimming range

„

Possible analog dimming

„

Integrated 2.5A power switch

„

700kHz switching frequency for small size

„

Adjustable OVP for cost-e ective output cap selection

„

Open/short LED protection

„

Thermal protection with auto-recovery

„

Thermally enhanced TSSOP-16 EDP package

„

Pb Free, Halogen Free, andWEEE/RoHS Compliant

„

Medium-sized LCD panel

„

Notebook Display

„

Automotive Car Navigation Display

„

Sub-Notebook and Tablet Computer Displays

„

Portable Media Players

The SC446 is a high-eciency multiple string WLED driver

with an integrated boost converter. It operates over a

wide input range from 4.5V to 27V with a maximum out-

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

can drive up to thirty WLEDs in 3 strings with current up

to 100mA per string. The string-to-string current match-

ing is 2% typical, 3% maximum. The overall eciency 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 eciency. 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 SC446 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, una ected

LED strings. This feature allows LCD panels to remain

viewable even under LED failure, wire disconnect, or

short-circuit conditions. The internal thermal shutdown

protects the IC from overheating at abnormal conditions.

The SC446 is available in a thermally-enhanced TSSOP-16

EDP package.

Typical Application Circuit



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