LM2755 Datasheet, PDF (1/21 Pages) National Semiconductor (TI) – Charge Pump LED Controller with I2C Compatible Interface in Micro SMD

LM2755
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SNVS433D – OCTOBER 2007 – REVISED APRIL 2013
LM2755 Charge Pump LED Controller with I²C-Compatible Interface in DSBGA Package
Check for Samples: LM2755
FEATURES
1
•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.
TYPICAL APPLICATION CIRCUIT
0.47 PF 0.47 PF
1 PF
C1- C1+ C2- C2+
VIN
POUT
1 PF
SCL ^LM2755
SDIO
D1
VIO
D2
SYNC
D3
HWEN
ISET _{GND ADDR}
12.5 k:
Capacitors:
TDK C1005X5R1A105M and C1005X5R1A474M ,
or 1 PF and 0.47 PF single capacitor equivalent
3.1 mm
C2
COUT
C1
ADR
VIO
SCL
SDIO
SYNC
HWEN
Dx Pins
CIN
RSET
Figure 1. Typical Application Circuit
Figure 2. Minimum Solution Size
1
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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