60V LED driver has 4A switch & PWM generator

April 14, 2015 // By Graham Prophet
LT3952 is a current mode step-up DC/DC converter with an internal 60V, 4A DMOS power switch. It is designed to drive high power LEDs in multiple configurations, and combines input and output current regulation loops with output voltage regulation to operate as a flexible current/voltage source.

LT3952’s 3V to 42V input voltage range suits it for a wide variety of applications, including automotive, industrial and architectural lighting. It can drive up to sixteen 350 mA 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. A frequency adjust pin permits the user to program the switching frequency between 200 kHz and 3 MHz. The device delivers over 90% efficiency while switching at 2 MHz in a tiny solution footprint. The LT3952 provides a very compact high power LED driver solution in a thermally enhanced TSSOP-28E package.

The chip 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°C to 125°C (junction) for the extended, and industrial grades, and a high temperature grade of -40°C to 150°C. Pricing starts at $3.95 (1000).

Linear Technology; www.linear.com/product/LT3952

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