Analog's charge pump regulator delivers highest accuracy in backlighting for color TFT displays

June 23, 2004
Analog Devices has introduced the ADM8845 charge pump regulator, designed to deliver the most accurate backlighting in micro color thin film transistor (TFT) liquid crystal displays (LCDs) used in cell phones, PDAs and digital cameras.
Analog ADM8845 Using advanced charge pump technology, the device drives up to six white light emitting diodes (LEDs), evenly diffusing light across the entire LCD panel. Precision monitoring of individual LED currents provides industry-leading matching, with less than1% error. Its high power efficiency (up to 88%), helps save battery power; and its small lead frame chip scale package (3 × 3 mm LFCSP) saves 44% board space compared to the nearest competitor.

The ADM8845?s excellent current matching is achieved by individually monitoring the current in each LED, using six individual current control blocks to achieve 1% maximum matching error. This ensures a uniform backlight across all areas of the LCD panel.

Two control inputs allow the LEDs to be switched on and off in two independent blocks of four LEDs and two LEDs, making the ADM8845 ideal for the latest clam-shell style mobile phones that feature both a main display and a smaller secondary display. The brightness of the LEDs can be adjusted by varying the input signal to these control pins.

To maximize power efficiency, the onboard charge pump automatically switches between 1×, 1.5× and 2× modes, depending on the input voltage from the battery. Soft-start circuitry limits the inrush current to prevent an abrupt start-up.

Pricing and Availability
Manufactured using CMOS process technology, the ADM8845 is available in a 16-lead LFSCP package. Samples are available today and production quantities will be available in July 2004. The ADM8845 is priced at $0.70 per unit in 10,000 piece quantities.