LM27964_07 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – White LED Driver System with I2C Compatible Brightness Control

August 2007
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 in-
ternal 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 display.
A single Keypad LED driver can power up to 16 keypad LEDs
with a current of 5mA each. The LM27964 has an I²C com-
patible 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 main-
taining 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 Leadless
Leadframe Package (LLP-24).
Features
■ ^{87% Peak LED Drive Efficiency}
■ ^{0.2% Current Matching between Current Sinks}
■ ^{Drives 6 LEDs with up to 30mA per LED in two distinct}
groups, for backlighting two displays (main LCD and sub
LCD)
■ ^{Dedicated Keypad LED Driver with up to 80mA of drive}
current
■ ^{Independent Resistor-Programmable Current Settings}
■ ^{I2C Compatible Brightness Control Interface}
■ ^{Adaptive 1×- 3/2× Charge Pump}
■ ^{Extended Li-Ion Input: 2.7V to 5.5V}
■ ^{Small low profile industry standard leadless package, LLP}
24 : (4mm x 4mm x 0.8mm)
■ ^{LM27964SQ-I LED PWM frequency = 10kHz,}
LM27964SQ-C LED PWM frequency = 23kHz
Applications
■ ^{Mobile Phone Display Lighting}
■ ^{Mobile Phone Keypad Lighting}
■ ^{PDAs Backlighting}
■ ^{General LED Lighting}
Typical Application Circuit
© 2007 National Semiconductor Corporation 201381
20138101
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