The LT3955’s 4.5V to 60V input voltage range suits a wide variety of applications, including automotive, industrial and architectural lighting. It uses an internal 3.5A, 80V N-channel MOSFET and can drive up to twelve 300mA white LEDs from a nominal 12V input, delivering in excess of 20W. It incorporates a high-side current sense, enabling use in boost mode, buck mode, buck-boost mode or SEPIC topologies. The LT3955 can deliver efficiencies of over 94% in the boost topology, eliminating the need for external heat sinking. A frequency-adjust pin permits the user to program the frequency between 100 kHz and 1 MHz, optimising efficiency while minimising external component size and cost. In with a 5 x 6mm QFN package, the LT3955 offers a compact high-power LED driver solution.
The internal PWM generator delivers dimming ratios as high as 25:1 or it can use an external PWM signal, delivering dimming ratios of up to 3,000:1 with Linear's True Color PWM Dimming. For less demanding dimming requirements, the CTRL pin can be used to provide a 10:1 analogue dimming range. Its fixed frequency, current-mode architecture offers stable operation over a wide range of supply and output voltages. Output short-circuit protection and open LED protection enhance system reliability. The LT3955’s ground-referenced voltage FB pin serves as the input for several LED protection features and makes it possible for the converter to operate as a constant-voltage source for charging applications.
The LT3955EUHE costs $3.75 (1000). An extended temperature version, or I grade, the LT3955IUHE, is also available, at $4.41.
Linear Technology; www.linear.com/product/LT3955