White-LED driver backlights LCD and keypad

摘要

DESIGNERS WIDELY USE white LEDs to backlight color LCDs and keypads in handheld devices, such as cell phones, MP3 players, GPS navigators, and PDAs. Their spectrum and brightness represent near-ideal light sources. One possible configuration for a phone or a phone/PDA combination is to have a group of three LEDs to light the display and six LEDs for the keypad. Figure 1 shows a method for driving all the LEDs with a single driver IC from Catalyst Semiconductor (www. catsemi.com), the CAT32. Power comes from a single lithium-ion battery cell.