CIE Components in Electronics
Linear Technology has unveiled the LT3797, a triple output DC/DC controller 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.
With a 2.5V to 40V input voltage range with transient ride through to 60V the device is suitable 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 90V of LEDs with LED currents in excess of 1A, delivering over 250W of power from a nominal 12V 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 and aach channel offers both robust open-LED and short-circuit protection in boost mode, providing the 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 optimise efficiency while reducing external component size. Its thermally enhanced 7mm x 8mm QFN package provides a highly compact solution footprint for 20W to 250W 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 analogue dimming via the CTRL pin and external synchronisation.
