LED driver offers PWM & 94% efficiency in boost mode

Posted By : Barney Scott
LED driver offers PWM & 94% efficiency in boost mode

The LT3952 is a current mode step-up DC/DC converter with an internal 60V, 4A DMOS power switch, specifically designed to drive high power LEDs in multiple configurations. It combines input and output current regulation loops with output voltage regulation to operate as a flexible current/voltage source. A 3-42V input voltage range means it suits automotive, industrial and architectural lighting applications.

The LT3952 can drive up to sixteen 350mA white LEDs from a nominal 12V input, delivering in excess of 15W. It incorporates a high side current sense, enabling its use in boost mode, buck mode, buck-boost mode or SEPIC topologies. Internal spread spectrum frequency modulation minimises EMI concerns.

The LT3952 delivers efficiencies of over 94% in the boost topology, eliminating the need for external heat sinking, and internal LED short-circuit protection enables added reliability required in most applications. A frequency adjust pin permits the user to programme the switching frequency between 200kHz and 3MHz, optimising efficiency while minimising external component size and cost. The LT3952 delivers over 90% efficiency while switching at 2MHz in a tiny solution footprint. The LT3952 provides a very compact high power LED driver solution in a thermally enhanced TSSOP-28E package.

The LT3952 has a gate driver for a PMOS LED disconnect switch, delivering dimming ratios of up to 4,000:1 using an external PWM signal. For less demanding dimming requirements, the CTRL pin can be used to offer a 10:1 analogue dimming range and an internal PWM generator can be used for 5:1 dimming.

The LT3952’s 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. Other features include frequency synchronisation, spread spectrum frequency modulation, programmable VIN undervoltage and overvoltage protection, and an input current limit and monitor.

The LT3952EFE is available in a thermally enhanced 28-lead TSSOP package. Three temperature grades are available, with operation from -40 to +125°C (junction) for the extended, and industrial grades, and a high temperature grade of -40 to +150°C. Pricing starts at $3.95 each in 1,000-piece quantities and all versions are available from stock.

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