POWER THREE WHITE LEDs DIRECTLY FROM 1-CELL Li+ WITH 0.3% BRIGHTNESS MATCHING
SUNNYVALE, CA-August 16, 2001-Maxim Integrated Products introduces the MAX1916 triple-output current regulator for biasing white LEDs in cell phones and PDAs with even brightness. It provides significantly better matching than traditional ballast resistor schemes and provides longer battery life. Traditional ballast resistors provide only 2:1 LED-to-LED current matching. The MAX1916 regulates three LED currents with better than ±0.3% matching, eliminating costly factory calibration and the need to purchase LEDs with matched forward voltages (VF).
The MAX1916 is the simplest and cheapest solution to powering white LEDs from a single-cell lithium-ion (Li+) battery. The complete solution consists of the MAX1916 and one chip-resistor to set the LED current. The EN pin allows simple ON/OFF logic-control and functions as the power input for the device.
The MAX1916 requires only 200mV dropout voltage at a 9mA load to match the LEDs brightness. This low dropout allows the LEDs to be powered directly from a single-cell Li+ battery for a longer time, extending battery life. Compared to ballast resistors, MAX1916 extends battery life by 350mV.
The MAX1916 can handle up to 60mA per LED. Other features include 2.5V to 5.5V input voltage range, low 40mA quiescent supply current, and thermal shutdown protection. The MAX1916 is available in a thin 6-pin SOT23 package with 1mm height and screened for the extended-industrial temperature range (-40° C to +85° C). Prices start at $0.99 (2500-up, FOB USA, recommended resale).
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