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 I
2C Compatible Interface
|
| • | Up to 90% Efficiency |
| • | Total Solution Size < 21mm
2
|
| • | Low Profile 20 Bump micro SMD 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 |
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 configured
to drive four, five or six LEDs for use in the main phone display, while the secondary group (Group B) can be configured
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 regulation is chosen, based on LED forward voltage, so that efficiency
is maximized over the input voltage range.
The LM2756 is available in National’s tiny 20-bump, 0.4mm pitch, thin micro SMD package.
Applications
| • | Dual Display LCD Backlighting for Portable Applications |
| • | Large Format LCD Backlighting |
| • | Display Backlighting with Indicator Light |
|
Typical Application Circuit
|
LM2756
