High Eciency Integrated Driver for
4-Strings of 150mA LEDs
SC441
POWER MANAGEMENT
September 28, 2010 1
www.semtech.com
NOT RECOMMENDED
FOR NEW DESIGNS
NOT RECOMMENDED FOR NEW DESIGNS: SEE SC441A
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% eciency
Wide 0.2% to 100% PWM dimming range
Possible analog dimming
Integrated 2.5A power switch
800kHz switching frequency for small size
Adjustable OVP for cost-eective output cap selection
Open/short LED protection
Thermal protection with auto-recovery
Thermally enhanced TSSOP-20 EDP package
Fully WEEE and RoHS compliant
Medium-sized LCD panel
Notebook Display
Automotive Car Navigation Display
Sub-Notebook and Tablet Computer Displays
Portable Media Players
The SC441 is a high-eciency multiple string WLED driver
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 2.5A 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 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 800kHz 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 SC441 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, unaected
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 SC441 is available in a thermally-enhanced TSSOP-20
EDP package.
Typical Application Circuit
4
VOUT
SS
PGND
IOSET
IO1-4
COMP
OVPIN
AGND
VIN
SW
PWM
EN
OVPRTN
SW
FFLAG
PGND
IOGND
SC441
4 Strings
1
10
Vin (4.5V -21V)
2
EDP
PGND
IOSET
IO1- 4
COMP
SS
AGND
VOUT
OVPIN
