HIGH-EFFICIENCY, SOT23, STEP-UP CURRENT SOURCE POWERS WHITE LEDs WITH UNIFORM BRIGHTNESS
SUNNYVALE, CA-May 15, 2001-Maxim Integrated Products introduces the MAX1848, which is the first high-efficiency, step-up DC-DC converter to regulate current, instead of voltage, to power white LEDs for backlights in cell phones and PDAs. This device powers two or three white LEDs in series, instead of in parallel, to eliminate brightness mismatch caused by different threshold voltages.
The MAX1848 fits in an 8-pin SOT23 package, and it contains an internal n-channel MOSFET switch that provides 85% efficiency, which is 40 percentage points higher than traditional doubling charge-pump solutions. Battery life is up to 1.8-times' longer, and input ripple and noise are lower than charge-pump solutions.
The input range is 2.6V to 5.5V for powering directly from a lithium-ion battery. The output can go as high as 13V and up to 60mA for powering up to three LEDs in series. The sense resistor is a standard, low-cost, 5-kilohm chip resistor that gives 5% current tolerance without requiring calibration. Other features include an input for digital control of the brightness from a DAC.
The MAX1848EKA repetitive is screened for the extended-industrial temperature range (-40°C to +85°C). Prices start at $1.25 (2500-up, U.S. recommended resale).
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