The LT3797 triple output DC/DC controller from Linear Technology is designed to drive three independent channels of LEDs. Its fixed frequency, current-mode architecture delivers constant, accurately regulated LED current over a wide range of supply and output voltages. Its 2.5 V to 40 V input voltage range with transient ride through to 60 V makes it ideal for automotive applications, which must operate through cold crank, stop/start and load dump scenarios as well as a wide range of industrial applications. Each of the LT3797's channels can drive a wide range of LED power in either step-up, step-down or SEPIC topologies. In a boost configuration, it powers three channels of up to 90 V of LEDs with LED currents in excess of 1A, delivering over 250 W of power from a nominal 12 V input with efficiencies as high as 93%. Each of the three channels is operated by an independent True Color PWM™ signal, enabling each channel to be dimmed to ratios as high as 3000:1. Each channel also offers both robust open-LED and short-circuit protection in boost mode, providing high safety and reliability designs required in automotive applications. A frequency adjust pin enables the user to program the frequency between 100kHz and 1MHz to optimize efficiency while minimizing external component size. Its thermally enhanced 7 mm x 8 mm QFN package provides a highly compact solution footprint for 20 W to 250 W LED applications.
The LT3797 is designed so that each channel can use the most suitable configuration to drive its LED string, whether step-up, step-down, and SEPIC or a combination of these. Its high-side current sense enables each channel to be used in the same or different configurations while rail-to-rail current sense enables outputs from 0V to 100V, offering a wide range of design flexibility. Other features include overvoltage and undervoltage lockout, 20:1 analog diming via the CTRL pin and external synchronization. The LT3797EUKG is available from stock in a thermally enhanced 52-lead 7 mm x 8 mm QFN package. 1,000-piece pricing starts at $4.95 each and it is available from stock. The LT3797IUKG is tested and guaranteed to operate from a -40 °C to 125 °C operating junction temperature. It's priced at $5.54 each in 1,000-piece quantities and is also available from stock.