Charge Pumps Brighten White LEDs

A pair of high-efficiency charge pumps, the AAT3140 and AAT3141, are designed specifically to power white LEDs in cell phones and other small battery-powered devices. Both produce current levels of up to 30 mA each on four current source outputs. The outputs can be operated individually or in parallel. Input voltage to the devices can range from 2.7V to 5.5V. The AAT3140 provides 32-position logarithmic scale LED brightness using the company’s Simple Serial Control single-wire digital input. This is an alternative to PWM signals used to control LED brightness. The AAT3141 offers the same features as the 3140 but adds addressability to its digital input control. Called Advanced Simple Serial Control, this interface allows the operation of multiple displays such as in clamshell cell phones. The device can independently control three LEDs to backlight a main display and one LED (or two in parallel) to backlight a sub-display. Both types are available in 12-pin TSOPJW packages rated over the _40°C to +85°C range. Price for the ATT3140 is $1.95 each/1,000. ADVANCED ANALOGIC TECHNOLOGIES INC.,Sunnyvale, CA. (408) 737-4600.