Power Electronics

Ultrahigh Efficiency White LED Drives

The MAX1984/MAX1985/MAX1986 white light-emitting diode (LED) drivers with individual regulators control the current of up to eight LEDs. Highly efficient (>95%) step-up regulators generate adequate voltage levels to keep all the current regulators in regulation. This results in over 90% LED drive efficiency.

The MAX1984/MAX1985/MAX1986 drive up to eight, six, and four LEDs, respectively. Each device has an LED select pin (SEL), which allows one of two subsets or all LEDs to be illuminated. The individual current regulators improve current matching between LEDs; open or shorted LEDs cannot affect the performance of other LEDs. The step-up regulators achieve high efficiency by using synchronous rectification. The internal N-channel switch and P-channel synchronous rectifier eliminate the need for external MOSFETs and diodes. The 1 MHz switching frequency allows for low-profile inductors and ceramic capacitors.

A versatile dimming interface accommodates analog, digitally adjusted pulse-width modulation (DPWM), and parallel control. Brightness is adjusted using a multi-mode dimming interface through a DPWM signal, a 2- or 3-bit parallel control interface, or an analog signal. If frequency is 10 kHz or above, the DPWM signal can be connected directly to the control pin without an external RC filter. These devices are available in a 4 mm x 4 mm thin QFN package.

A preliminary data sheet for this product is available from Maxim at www.maxim-ic.com/PRGraphics/PRPDF/MAX1984DS.pdf.

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