100-V high-side current sense DC/DC controller helps to regulate a constant-current or constant-voltage for HBLEDs

April 18, 2012 // By Paul Buckley
Linear Technology has released a 100 V, high-side current sense DC/DC controller designed to regulate a constant-current or constant-voltage that is ideal for driving high brightness (HB) LEDs.

The LT3796’s 6 V to 100 V input voltage range supports a wide variety of applications, including automotive, industrial and architectural lighting. The device uses an external N-channel MOSFET and can drive up to 85 V of white LEDs from a nominal 12 V input, delivering in excess of 50 Watts.

The LT3796 is ideal for charging batteries or supercaps at constant current and voltage. The LT3796 incorporates a high-side current sense, enabling its use in boost, buck, buck-boost or SEPIC and flyback topologies. Additionally, it offers both input and output current limiting and monitoring for added reliability and design flexibility.

The controller can deliver efficiencies of over 94% in boost mode, minimizing the need for external heat sinking. A frequency adjust pin enables the user to program the frequency between 100 kHz and 1 MHz, optimizing efficiency while minimizing external component size and cost. Combined with a thermally enhanced TSSOP-28 package, the LT3796 offers a highly compact HB LED driver or charger solution.

The LT3796 uses True Color PWM dimming, which delivers constant LED color with dimming ranges of up to 3,000:1. For less demanding dimming requirements, the CTRL pin can be used to offer a 10:1 analog dimming range. Its fixed frequency, current-mode architecture ensures stable operation over a wide range of supply and output voltages.

Robust open and short-circuit protection maximize overall system reliability, whereas C/10 detection optimizes both battery and supercap charging designs. Additional features include frequency synchronization, programmable UVLO and a programmable fault restart timer.