Linear Technology's LT3597 is a 60V, 1MHz,
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. From a 48V input, the LT3597 can
drive up to three strings of LEDs, each with up to ten 100mA LEDs in series,
delivering efficiencies of over 90 percent. The LT3597's multichannel
capability makes it useful for backlighting LED billboards as well as
industrial, automotive and medical displays. Similarly, its input voltage range
of 6 to 60V makes it well suited for industrial, automotive and medical
applications. Each LED string can be independently programmed to deliver up to
100mA 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 200kHz to 1MHz 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. The switching frequency is synchronizable to an external clock. The
LT3597's thermally enhanced 5 x 8mm QFN package provides a compact solution
footprint for LED lighting applications.
The LT3597 uses three
independent 400mA, 60V 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.
An industrial grade
version, the LT3597IUHG is tested and guaranteed to operate from a -40 to 125C
operating junction temperature.
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