White LED driver System with I2C Compatible brightness control

The LM27964 is a charge-pump-based white-LED driver that is ideal for mobile phone display backlighting. The LM27964 can drive up to 6 LEDs in parallel along with multiple keypad LEDs, with a total output current up to 180mA. Regulated internal current sources deliver excellent current matching in all LEDs.

The LED driver current sources are split into two independently controlled groups. The primary group (4 LEDs) can be used to backlight the main phone display and the second group (2 LEDs) can be used to backlight a secondary display. A single Keypad LED driver can power up to 16 keypad LEDs with a current of 5mA each. The LM27964 has an I2C compatible interface that allows the user to independently control the brightness on each bank of LEDs.

The LM27964 works off an extended Li-Ion input voltage range (2.7V to 5.5V). The device provides excellent efficiency without the use of an inductor by operating the charge pump in a gain of 3/2, or in Pass-Mode. The proper gain for maintaining current regulation is chosen, based on LED forward voltage, so that efficiency is maximized over the input voltage range.

The LM27964 is available in TI's small 24-pin WQFN Package (WQFN-24).