Step-down DC/DC converter drives up to three LED strings

Milpitas, Calif. — Linear Technology offers a 60-V, 1-MHz, step-down DC/DC converter designed to operate as a three-channel, constant current LED driver. Each channel of the LT3597 contains a constant current sink LED driver with a dedicated adaptive-output buck converter. This design offers maximum efficiency for applications, such as RGB displays, which require different output voltages for each LED string, said Linear Tech.
From a 48-V input, the LT3597 can drive up to three strings of LEDs, each with up to ten 100-mA LEDs in series, delivering efficiencies of over 90 percent. The LT3597 device’s multi-channel capability makes it suitable for backlighting LED billboards as well as industrial, automotive and medical displays. The device’s input voltage range of 6 V to 60 V also makes it well suited for industrial, automotive and medical applications.

Each LED string can be independently programmed to deliver up to 100 mA of LED current with +/- 2 percent current matching between strings. Each channel can be independently dimmed with True Color PWM dimming, offering dimming ratios as high as 10,000:1. A programmable 200-kHz to 1-MHz fixed frequency operation and current-mode architecture ensures stable operation over a wide range of supply and output voltages, minimizing the size of external components, said Linear Tech.

The LT3597 uses three independent 400-mA, 60-V internal switches to provide step-down constant current sources. The internal buck converters use an adaptive feedback loop to regulate the output voltage slightly higher than the required LED voltage to ensure maximum efficiency. If any of the LED strings experience an open or short-circuit, the LT3597 will continue to regulate the other strings and signal the FAULT pin. Additional features include LED current derating based on junction temperature and/or LED temperature and LED disconnect in shutdown.

The LT3597EUHG is available in a 39-lead, 5 x 8-mm QFN package.

Availability: All versions are available from stock.
Pricing: Starts at $3.95 each in quantities of 1,000. An industrial grade version, the LT3597IUHG is tested and guaranteed to operate from a -40°C to +125°C operating junction temperature and is priced at $4.54 each in quantities of 1,000.