LM2756 Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – Multi-Display Inductorless LED Driver with 32 Exponential Dimming Steps in μSMD

October 2007
LM2756
Multi-Display Inductorless LED Driver with 32 Exponential
Dimming Steps in µSMD
General Description
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.
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.
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.
The LM2756 is available in National’s tiny 20-bump, 0.4mm
pitch, thin µSMD package.
Features
■ ^{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}
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}
■ ^{Internal Soft-Start Limits Inrush Current}
■ ^{True Shutdown Isolation for LED’s}
■ ^{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
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