Electronic Design

DC-DC Converters Drive LEDs In High-Current Applications

A pair of dc-dc converters is specifically designed to drive high-current LEDs at a constant current. The LT3478EFE and LT3478EFE-1 from Linear Technology feature a 2.8- to 36-V input range that suits a wide array of applications, including automotive, industrial, and architectural lighting. In boost mode, the devices can drive six 700-mA LEDs in series from a 12-V input. The LT3478-1 uses an internal current-sense resistor, limiting output current to 1 A, while the LT3478 uses an external sense resistor to extend the maximum LED current to 4.5 A. Both deliver efficiencies up to 90% in boost mode.

The converters use True Color PWM dimming, which ensures constant LED color with dimming range up to 3000:1. Their fixed-frequency, current-mode architecture offers stable operation over a wide range of supply and output voltages. A frequency-adjust pin allows users to program the frequency between 200 kHz and 2.25 MHz in order to optimize efficiency while minimizing external component size.

The LT3478EFE and LT3478EFE-1 are available from stock in a thermally enhanced, 16-lead TSSOP-16E package. Prices start at $3.60 each for both versions. Extended temperature versions, the LT3478IFE and LT3478IFE-1, are also available from stock. Their prices start at $4.32 each in 1000-piece quantities. Visit www.linear.com.

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