1FEATURES

2• 90% Peak Efficiency

• Total solution size < 13mm2

• No Inductor Required: Only 4 Inexpensive

Ceramic Caps

• 3 Independently Controlled Constant Current

Outputs

• Programmable Trapezoidal Dimming

Waveform on Each Output

• Programmable Timing Control Via Internal

Registers and External Clock Synchronization

Input

• 32 Exponential Dimming Steps with 800:1

Dimming Ratio

• Programmable Brightness Control via I2C-

Compatible Interface

• Hardware Enable Pin

• Wide Input Voltage Range: 2.7V to 5.5V

• Tiny 18-bump Thin DSBGA : 1.8mm x 1.6mm x

0.6mm.

APPLICATIONS

• Indicator LEDs

• Keypad LED Backlight

• Display LED Backlight

• Fun-light LEDs

DESCRIPTION

The LM2755 is a charge-pump-based, constant

current LED driver capable of driving 3 LEDs with a

total output current up to 90mA. The diode current

waveforms of each LED can be trapezoidal with

timing and level parameters (rise time, fall time, high

level, low level, delay, high time, low time)

programmed via an I2C-compatible interface. The 32

brightness levels found on the LM2755 are

exponentially spaced (as opposed to linearly spaced)

to better match the response of the human eye to

changing brightness levels.

The device requires only four small and low-cost

ceramic capacitors. The LM2755 provides excellent

efficiency without the use of an inductor by operating

the charge pump in a gain of 3/2 or in a gain of 1.

Maximum efficiency is achieved over the input

voltage range by actively selecting the proper gain based on the LED forward voltage requirements.

The pre-regulation scheme used by the LM2755 is

optimized to ensure low conducted noise on the

input. An internal soft-start circuitry eliminates high

inrush current at start-up. The LM2755 consumes

3μA (typ.) of supply current in shut-down.

The LM2755 is available in Texas Instruments' tiny

18-bump thin DSBGA package.