REGULATED CHARGE PUMP GIVES 33% BETTER EFFICIENCY FOR POWERING WHITE LEDs
SUNNYVALE, CA-February 19, 2002-Maxim Integrated Products introduces the MAX1910/MAX1912 regulated charge pumps for high-efficiency white-LED backlight supplies in cellphone, PDA, and digital camera applications. The MAX1912 1.5x regulated pump provides higher efficiency and lower noise step-up output than conventional 2x charge pumps. At a typical lithium-ion battery voltage supply of 3.6V, the MAX1912 is 64% efficient versus 48% for a traditional 2x charge pump-a 33% improvement. The MAX1910 automatically switches between 1.5x and 2x modes to maintain constant voltage for applications with wide battery voltage ranges.
The MAX1910/MAX1912 permit the user to select voltage-mode or current-mode regulation as the brightness matching method. In current mode, the FB pin is regulated at 200mV, allowing the LED brightness to be matched directly by its currents. In voltage mode, the output is regulated to a constant to permit sufficient headroom to match the LED brightness using ballast resistors. Output voltage tolerance is ±3%.
The MAX1910/MAX1912 output current capability is up to 120mA for powering multiple LEDs in parallel with a supply voltage range of 2.7V to 5.3V.
These devices use a unique 750kHz fixed-frequency pulse-width-modulated (PWM) switching architecture to minimize noise harmonics and input-current ripple, permitting small ceramic input capacitors. In logic-controlled shutdown, the supply current is cut to 1µA, and the LED load is completely disconnected from the input to maximize battery life.
The MAX1910/MAX1912 are available in small 1mm-high 10-pin µMAX packages screened for the extended-industrial temperature range (-40°C to +85°C). Prices start at $1.05 (1000-up, FOB USA). The MAX1912EVKIT (evaluation kit) is available to speed designs.
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