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HB LED driver tailored for outdoor LCDs

Posted: 21 May 2010 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? high-brightness LED? LCD?

SC446 HB LED driver

Semtech Corp. has released the SC446 three-channel high-brightness LED (HB LED) driver with an integrated 2.5A boost power switch.

The device is capable of driving up to 36 HB LEDs at up to 100mA per channel. The SC446 operates across a wide input voltage range of 4.5V to 27V, making it ideal for use with automotive batteries or regulated 5V, 12V or 24V power supplies. The SC446 expands Semtech's popular HB LED driver platform for mid-size LCD panels in indoor/outdoor displays for automotive, industrial, white goods, avionics, medical and gaming equipmentapplications where the high reliability, shock resistance and mercury-free benefits of LEDs are displacing traditional fluorescent (CCFL) bulbs.

These types of rugged LCD panels require an ultrabright light source for viewing in direct sunlight. The extra design tolerance of the SC446 meets the demands of time and temperature. The SC446 provides exceptional LCD illumination with up to 100mA per channel. It also features a rugged, 16-pin thermally enhanced TSSOP package for low operating temperature and long life at high ambient conditions. Additionally, 1mm pin spacing minimizes the risk of pin-to-pin faults arising from PCB contamination in harsh environments.

"The transition from CCFL to LED backlights gives LCD panel manufacturers and systems integrators a simple, cost-effective option for improving the temperature profile and shock ruggedness of their designs," said Steve Hawley, Semtech product marketing manager for LED lighting and displays. "The SC446 offers a driver solution that matches the reliability of the high brightness LEDs themselves."

The SC446 has a low-loss internal boost switch to provide efficiency of greater than 92%. Up to 50kHz PWM dimming eliminates audio noise problems. The optimum LED output voltage is maintained dynamically by the internal DC/DC current mode controller. Channels can be paralleled for applications requiring low component stress and minimum temperature rise. Channels can also be independently disabled to fit smaller panel designs. The controller switching frequency is optimized at 700kHz for minimum external L/C filter size and highest operating efficiency.

Additionally, the SC446 provides a smooth transition from boost to bypass operating mode, when the input voltage is greater than the output voltage. Current sinks are rated up to 40V. The controller is compatible with the SEPIC converter topology, where the input voltage is greater than, or less than, the output voltage.

The SC446 LED driver has an exposed thermal paddle for optimum heat sinking. The SC446 is Pb-free, halogen-free and fully RoHS-compliant.

The SC446 is available immediately in production quantities and is priced at $1.65 each in 2,500-piece lots. The ordering code is SC446TETRT. Evaluation boards (SC446EVB) are also available. Semtech offers comprehensive design assistance, including field- and factory-based support.

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