LM27964 Datasheet, PDF (1/13 Pages) National Semiconductor (TI) – White LED Driver System with I2C Compatible Brightness Control

October 2005
LM27964
White LED Driver System with I2C Compatible
Brightness Control
General Description
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 indepen-
dently 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 dis-
play. 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 effi-
ciency 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 National’s small 24-pin Lead-
less Leadframe Package (LLP-24).
Features
n 87% Peak LED Drive Efficiency
n 0.2% Current Matching between Current Sinks
n Drives 6 LEDs with up to 30mA per LED in two distinct
groups, for backlighting two displays (main LCD and sub
LCD)
n Dedicated Keypad LED Driver with up to 80mA of drive
current
n Independent Resistor-Programmable Current Settings
n I²C Compatible Brightness Control Interface
n Adaptive 1x- 3/2x Charge Pump
n Extended Li-Ion Input: 2.7V to 5.5V
n Small low profile industry standard leadless package,
LLP 24 : (4mm x 4mm x 0.8mm)
n LM27964SQ-I LED PWM frequency = 10kHz,
LM27964SQ-A LED PWM frequency = 23kHz
Applications
n Mobile Phone Display Lighting
n Mobile Phone Keypad Lighting
n PDAs Backlighting
n General LED Lighting
Typical Application Circuit
© 2005 National Semiconductor Corporation DS201381
20138101
www.national.com