SC445 Datasheet, PDF (1/1 Pages) Semtech Corporation – High Efficiency Integrated Driver for 4-Strings of 150mA LEDs

SC445
POWER MANAGEMENT
Features
High Efficiency Integrated Driver for
4-Strings of 150mA LEDs
Description
 Wide input voltage range from 4.5V to 27V
 Sustain fast Vin fluctuation up to 5v/µs
 42V 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
 Enable 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
 Short LED protection enable/disable
 Thermal protection with auto-recovery
 Thermally enhanced TSSOP-20 EDP package
 Lead-free, Halogen-Free and WeEE/RoHS Compliant
Applications
 Medium-sized LCD panel
 Notebook Display
 Automotive Car Navigation Display
 Sub-Notebook and Tablet Computer Displays
 Portable Media Players
The SC445 is a high-efficiency multiple string WLED driver
with an integrated boost converter. It operates over a
wide input range from 4.5V to 27V and can sustain fast
Vin transient up to 5V/µs. It can drive up to forty WLEDs in
4 strings with current up to 150mA per string. The string-
to-string current matching is 2% typical, 3% maximum.
The overall efficiency is greater than 90% due to the low
current sense voltage and a low-impedance internal pow-
er 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 SC445 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 SC445 is available in a thermally-enhanced TSSOP-20
EDP package.
Typical Application Circuit
Vin (4.5V -27V)
SW
VIN
SCP_EN
EN
SW
VOUT
OOVVPPIINN
FFLAG
PWM _SC445
4
IOIO11- -44
COMP
IIOOSSEETT
AAGGNNDD
SS
EDP
PPGGNNDD
IOGND
PGND
1
2
4 Strings
12
Revision 2.1