LM2755 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – Charge Pump LED Controller with I2C Compatible Interface in Micro SMD

October 2007
LM2755
Charge Pump LED Controller with I2C Compatible Interface
in Micro SMD
General 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) pro-
grammed via an I²C compatible interface. The 32 brightness
levels found on the LM2755 are exponentially spaced (as op-
posed 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 ca-
pacitors. 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 National’s tiny 18-bump thin micro
SMD package.
Features
■ ^{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 micro SMD: 1.8mm x 1.6mm x 0.6mm}
Applications
■ ^{Indicator LEDs}
■ ^{Keypad LED Backlight}
■ ^{Display LED Backlight}
■ ^{Fun-light LEDs}
Typical Application Circuit
20180901
20180904
Minimum Solution Size
© 2007 National Semiconductor Corporation 201809
www.national.com