October 2007
LM2756
Multi-Display Inductorless LED Driver with 32 Exponential
Dimming Steps in µSMD
General Description
Features
The LM2756 is a highly integrated, switched-capacitor, multi-
display LED driver that can drive up to 8 LEDs in parallel with
a total output current of 180mA. Regulated internal current
sources deliver excellent current and brightness matching in
all LEDs.
Drives up to 8 LEDs with up to 30mA of Diode Current
Each
32 Exponential Dimming Steps with 800:1 Dimming Ratio
for Group A (Up to 6 LEDs)
8 Linear Dimming States for Groups B (Up to 3 LEDs) and
D1C (1 LED)
Programmable Auto-Dimming Function
3 Independently Controlled LED Groups Via I2C
■
■
■
The LED driver current sinks are split into three independently
controlled groups. The primary group (Group A) can be con-
figured to drive four, five or six LEDs for use in the main phone
display, while the secondary group (Group B) can be config-
ured to drive one, two or three LEDs for driving secondary
displays, keypads and/or indicator LEDs. An additional driver,
D1C, is provided for additional indicator lighting functions.
■
■
Compatible Interface
Up to 90% Efficiency
Total Solution Size < 21mm2
■
■
■
Low Profile 20 Bump µSMD Package
(1.615mm × 2.015mm × 0.6mm)
0.4% Accurate Current Matching
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 regula-
tion is chosen, based on LED forward voltage, so that effi-
ciency is maximized over the input voltage range.
■
■
■
■
Internal Soft-Start Limits Inrush Current
True Shutdown Isolation for LED’s
The LM2756 is available in National’s tiny 20-bump, 0.4mm
pitch, thin µSMD package.
Wide Input Voltage Range (2.7V to 5.5V)
Active High Hardware Enable
■
Applications
Dual Display LCD Backlighting for Portable Applications
■
■
■
Large Format LCD Backlighting
Display Backlighting with Indicator Light
Typical Application Circuit
30009701
© 2007 National Semiconductor Corporation
300097
www.national.com