Its 2.5V to 40V input voltage range with transient tolerance up to 60V makes it suitable for automotive applications 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.
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 100 kHz and 1 MHz to optimise efficiency while minimising external component size. Its thermally-enhanced 7 x 8 mm QFN package provides a 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, or 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.
It comes in a thermally enhanced 52-lead 7 x 8 mm QFN package for $4.95. (1,000). For extended temperature ranges, LT3797IUKG operates over -40°C to 125°C operating junction temperature, for $5.54 (1,000).
Linear Technology; www.linear.com/product/LT3797