March 26, 2010
POWER MANAGEMENT
1
10-Channel, Integrated, High Eciency
120 White LED Driver
SC442
Typical Application Circuit
Features
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
Description
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.
Enable
Dimming
VOUT
SS
PGND
FS
SCPSET
IO1- 10
OVFB
IOGND
PWM
AGND
VIN = 4.5V – 21V
EN
COMP
VIN
SW
SCPEN
SCPEN
AGND
IOSET
SW
SYNC
10
Up to 120WLEDs
VOUT = Up to 42V
6.8uH
1.47k
12nF
47nF
