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Driver IC handles up to 80 white LEDs

Posted: 22 Dec 2009 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? DC/DC controller? white LED?

Linear Technology debuts the LT3760, an eight-channel LED driver, using a step-up DC/DC controller that can drive up to a 45V string of 100mA LEDs per channel. It features an internal 60V, 1MHz DC/DC boost mode controller that operates as a constant current LED driver for up to 80 white LEDs.

From a 12V input, the LT3760 can drive 8 channels, each with up to ten 100mA white LEDs in series while delivering efficiencies exceeding 92 percent. Its multichannel capability makes it suitable for medium and large-sized TFT-LCD backlighting applications. Its input voltage range of 6V to 40V makes it fit for automotive, avionic, HDTV and industrial display applications.

The LT3760 offers 2.0 percent (0.7 percent typical) LED current matching to ensure uniform brightness of the display. Dimming ratios as high as 3,000:1 can be attained by using True Color PWM dimming. A programmable 100kHz to 1MHz fixed frequency operation and current mode architecture offers stable operation over a wide range of supply and output voltages while minimizing the size of the external components. Also, the switching frequency can be synchronized with an external clock. Its thermally enhanced TSSOP-28 package offers a highly compact solution footprint for most LED backlighting applications.

The LT3760 uses an external n-channel MOSFET switch to provide a boost mode constant current source. However, even when VIN exceeds VOUT, the LT3760 will continue to accurately regulate the LED current. The internal boost controller uses an adaptive feedback loop to drive up to eight channels of ten 100mA LEDs to regulate the output voltage slightly higher than the required LED voltage to ensure maximum efficiency. If any of the LED strings experience an open circuit, the LT3760 will continue to regulate the existing strings and signal the FAULT alert pin. If higher current LEDs are required, multiple strings can be combined, enabling the LT3760 to drive up to four channels of ten 200mA LEDs or two channels of ten 400mA LEDs. Additional features include programmable LED current derating based on junction temperature and LED temperature and programmable output voltage limiting when all LED strings are disconnected.

The LT3760EFE is available in a thermally enhanced 28-lead TSSOP package and is priced at $4.25 each in 1,000 piece quantities. An industrial grade version, the LT3760IFE is tested and guaranteed to operate from a -40C to 125C operating junction temperature and is priced at $5 each in 1,000-piece quantities. All versions are available from stock.

For application notes on LED driver click here.

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