SC441A Datasheet, PDF (1/20 Pages) Semtech Corporation – High Efficiency Integrated Driver for 4-Strings of 150mA LEDs

SC441A
POWER MANAGEMENT
Features
High Efficiency Integrated Driver for
4-Strings of 150mA LEDs
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 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
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 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 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.
Applications
 Medium-sized LCD panel
 Notebook Display
 Automotive Car Navigation Display
 Sub-Notebook and Tablet Computer Displays
 Portable Media Players
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
Vin (4.5V -21V)
SW
VIN
EN
SW
VOUT
OOVVPPIINN
FFLAG
OVPRTN
PWM
SC441A
4
IOIO11- -44
COMP
IIOOSSEETT
AAGGNNDD
SS
EDP
PPGGNNDD
IOGND
PGND
1
2
4 Strings
10
July 23, 2009
www.semtech.com _