National Semiconductor LM2796 Manuals

National Semiconductor LM27961 Dual-Display White LED Driver with 3/2x Switched Capacitor Boost handbook

LM27961 is a charge-pump-based white-LED driver that is ideal for mobile phone display backlighting. It can drive 4 LEDs for a main phone display backlight and 3 LEDs for a sub-display backlight. The driver provides excellent current and brightness matching in all LEDs. The LED driver current sources are split into two independently controlled groups. The primary group (Group A) can be used to backlight a main phone display with up to 4 LEDs, with low-side current drivers accommodating common-anode-type LEDs. The second group (Group B) can backlight a secondary display with up to 3 LEDs, with high-side current drivers accommodating common-cathode-type LEDs. Both Group A and Group B can also drive standard two-terminal LEDs, and provide other general lighting functions (keypad lighting, fun lighting, etc). The brightness of the two LED groups can be adjusted independently with external resistors. The LM27961 works off an extended Li-Ion input voltage range (2.7V to 5.5V), achieving voltage boost with a high-efficiency 3/2x-gain charge pump. The LM27961 is available in National’s chip-scale 18-bump micro SMD package.