November 22, 2013 – Linear Technology Korea (CEO Hong Sa-gwak) announced the launch of a triple output DC/DC controller (product name: LT3797) designed to drive three independent LED channels. The fixed frequency, current mode architecture provides precisely regulated LED constant current across a wide range of input and output voltages. With an input voltage range of 2.5V to 40V and tolerance for transient overvoltage of 60V, it is ideal for automotive applications. These automotive applications must operate through cold crank, start/stop, and load dump scenarios as well as a wide range of industrial applications.

Each channel of the LT3797 can drive a wide range of LED power in boost, buck, or SEPIC topology. In boost configuration, this product supplies up to three LED channels of 90V with LED current exceeding 1A, delivering 250W power from a 12V input and achieving efficiency as high as 93%. Each of the three channels is operated by its own True Color PWM™ signal, allowing each channel to implement dimming effects at ratios as high as 3000:1. Each channel also provides both robust open LED and short-circuit protection in boost mode, realizing the high safety and reliability required in automotive applications. Through the frequency adjustment pin, users can program the frequency between 100kHz and 1MHz to optimize efficiency, and external component size can be minimized. The 7mm x 8mm QFN package with improved thermal performance provides a very compact solution footprint suitable for 20W to 250W LED applications.

The LT3797 is designed to allow each channel to use the optimal configuration environment to drive an LED string, whether in boost, buck, SEPIC, or a mix of these configurations. Through high-side current sensing, each channel can be used in identical or different configuration environments, and rail-to-rail current sensing realizes 0V to 100V output, providing extensive design flexibility. Other features include overvoltage, undervoltage lockout, 20:1 analog dimming through the CTRL pin, and external synchronization capability.

The LT3797EUKG is available in a 52-pin 7mm x 8mm QFN package with enhanced thermal performance. It is priced at $4.95 per unit at a quantity of 1,000 and is available immediately. The LT3797IUKG is tested and guaranteed to operate at a junction temperature of -40°C to 125°C. This product is priced at $5.54 per unit at a quantity of 1,000 and is available immediately. For detailed information, refer to www.linear.com/product/LT3797.

Photo caption: High Current Triple Output LED Driver

Product Features: LT3797

• Three independent LED driver channels
• Wide input voltage range: 2.5V to 40V with 60V transient overvoltage tolerance
• Rail-to-rail LED current sensing: 0V to 100V
• 3,000:1 True Color PWM™ dimming
• Gate driver for PMOS LED disconnect
• Operates in boost, buck, buck-boost SEPIC, or flyback topology
• Open LED protection
• Short-circuit protection even in boost configuration
• Error flag per channel
• Programmable VIN undervoltage and overvoltage lockout
• Adjustable switching frequency: 100kHz to 1MHz
• Synchronization capability with external clock
• CTRL pin providing analog dimming
• Programmable soft start
• 52-pin QFN package