SC442 Datasheet, PDF (1/1 Pages) Semtech Corporation – 10-Channel, Integrated, High Efficiency 120 White LED Driver

SC442
POWER MANAGEMENT
10-Channel, Integrated, High Efficiency
120 White LED Driver
Features
Description
 Wide input voltage range from 4.5V to 21V
 42V maximum operating output voltage
 Programmable LED current up to 30mA per string
 +/- 1% current matching
 Integrated 3A switch
 Low current sink voltage
 Up to 91% efficiency
 Flexible LED configurations
Mismatched LED channels
Disable individual channel(s)
Parallel channels for high LED current
 PWM dimming capability
Up to 50kHz dimming frequency
>500:1 dimming range
 Switching frequency: 500kHz - 1MHz
 Parallel device operation with Sync Pin
 Protection features:
Adjustable OVP
Cycle-by-cycle current limit
LED short channel with disable /Open channnel
Over-Temperature protection
 MLPQ-28 lead-free package (WEEE and RoHS compliant),
4×4mm × 0.6mm
Applications
 Automotive LCD Backlighting
 Desktop monitors
 Notebook PCs
 Portable TVs
The SC442 is a 10-channel, high efficiency integrated step-up
(boost) driver IC capable of powering up to 120 WLEDs. The device
has a wide input voltage of 4.5V to 21V with no internal regulator
or bypass capacitor required. The wide input range, up to 42V
output voltage and flexible implementation make it the ideal LED
backlight driver solution for medium to large LCD displays. The
current sink channels are programmed with an external resistor
up to 30mA each.
Channel-channel current matching is +/-1% . The device disables
open or shorted LEDs by disabling only the affected LED channel;
thus increasing LCD panel life. Channel-channel LED mismatch
voltage is accomodated by adjusting the SCPSET resistor. The
current sink channels may be operated in parallel for increased
LED current. Unused channels are be disabled by connecting the
pin to the input voltage.
Losses in the switching device and current sinks are minimized
across the operating range; yielding >90% efficiency and excel-
lent battery life for portable systems.
The device accepts PWM dimming up to 50kHz. Maximum dim-
ming range is greater than 500:1 with excellent linearity for opti-
mum PWM dimming characteristics. The high frequency dimming
capability (>20kHz) eliminates audio emissions and allows small
ceramic output capacitors.
Switching frequency is programmable from 200kHz to 1MHz;
allowing efficiency versus L/C sizing tradeoffs across the input/
output voltage range. Alternatively, the SYNC pin allows the
designer to synchronize the switching frequency to an external
system clock and, if necessary, a parallel SC442 device - eliminating
potential system intermodulation and interference problems.
Over-temperature shutdown protects the IC from over-heating
under abnormal conditions. The device is available in a small
4mmx4mm MLPQ-28 pin package with 0.6mm maximum height
and is fully WEEE and RoHS compliant.
Typical Application Circuit
VIN = 4.5V– 21V
6.8uH
VOUT = Up to 42V
Enable
Dimming
SCPEN
1.47k 12nF
47nF
SW
VIN
SYNC
SW
VOUT
OVFB
COMP
AGND
SS
IO1- 10
FS
IOSET
EN
SCPSET
PWM
IOGND
SCPEN
AGND
PGND
10
Up to 120WLEDs
March 26, 2010