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Small WLED drivers tout 92% efficiency

Posted: 06 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:white-LED drivers? WLED? high efficiency?

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Maxim Integrated Products has released the MAX8901A/MAX8901B claimed to be the smallest, highest efficiency white-LED (WLED) drivers, achieving up to 92 percent efficiency while driving a string of 2 to 6 WLEDs.

The 2mm x 2mm devices operate from a fixed 750kHz switching frequency, which enables the use of 1?F input and 0.1?F output capacitors. Designed to drive 2 to 6 WLEDs for backlighting, the MAX8901A/MAX8901B are designed for the 1.5- to 4inch LCDs used in battery-operated devices such as smart phones, PDAs, portable media players, GPS devices, and digital still cameras.

In addition, the MAX8901A/MAX8901B provide a single input to enable the IC and to control LED intensity. With the LED current proportional to the PWM duty cycle, the MAX8901A uses a direct-PWM input to regulate LED intensity. In contrast, the MAX8901B uses single-wire, serial-pulse dimming that reduces LED intensity in 32 linear steps.

Full-scale LED current for serial-pulse dimming is 24.75mA, and each step is 0.75mA. Besides providing flexible dimming control, the MAX8901A/MAX8901B integrate robust protection features: internal soft-start to eliminate inrush currents during startup, input overvoltage protection, LED overvoltage protection, undervoltage lockout, and thermal shutdown. To conserve battery power, these WLED drivers consume only 0.1mA in shutdown mode.

The MAX8901A/MAX8901B are available in a space-saving, thermally enhanced, 2mm x 2mm, 8-pin TDFN package that is fully specified over the -40C to 85C extended temperature range. Prices start at $1.25 (1000-up, FOB USA).

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