LP8550_14 Datasheet, PDF (1/49 Pages) Texas Instruments – LP8550 High-Efficiency LED Backlight Driver for Notebooks

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LP8550
SNVS657E – SEPTEMBER 2010 – REVISED SEPTEMBER 2014
LP8550 High-Efficiency LED Backlight Driver for Notebooks
1 Features
•1 High-Voltage DC/DC Boost Converter with
Integrated FET with Four Switching Frequency
Options: 156/312/625/1250 kHz
• 2.7-V to 22-V Input Voltage Range to Support 1x
to 5x Cell Li-Ion Batteries
• Programmable PWM Resolution
– 8 to 13 True Bits (Steady State)
– Additional 1 to 3 Bits Using Dithering During
Brightness Changes
• I²C and PWM Brightness Control
• Automatic PWM & Current Dimming for Improved
Efficiency
• PWM output frequency and LED Current set
through Resistors
• Optional Synchronization to Display VSYNC
Signal
• Six LED Outputs with LED Fault (Short/Open)
Detection
• Low Input Voltage, Overtemperature, Overcurrent
Detection, and Shutdown
• Minimum Number of External Components
2 Applications
• Notebook and Netbook LCD Display LED
Backlight
• LED Lighting
3 Description
The LP8550 is a white-LED driver with integrated
boost converter. It has six adjustable current sinks
which can be controlled by PWM input or with I²C-
compatible serial interface. The boost converter has
adaptive output voltage control based on the LED
driver voltages. This feature minimizes the power
consumption by adjusting the voltage to lowest
sufficient level in all conditions.
LED outputs have 8-bit current resolution and up to
13-bit PWM resolution with additional 1- to 3-bit
dithering to achieve smooth and precise brightness
control. Proprietary Phase Shift PWM control is used
for LED outputs to reduce peak current from the
boost converter, thus making the boost capacitors
smaller. The Phase Shifting scheme also eliminates
audible noise.
Automatic PWM dimming at lower brightness values
and current dimming at higher brightness values can
be used to improve the optical efficiency. Internal
EEPROM is used for storing the configuration data.
This makes it possible to have minimum external
component count and make the solution very small.
The LP8550 has safety features which make it
possible to detect LED outputs with open or short
fault — low input voltage and boost overcurrent
conditions are monitored, and chip is turned off in
case of these events. Thermal de-rating function
prevents overheating of the device by reducing
backlight brightness when set temperature has been
reached.
Device Information⁽¹⁾
PART NUMBER
PACKAGE
BODY SIZE (MAX)
LP8550
DSBGA (25)
2.49 x 2.49 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Simplified Schematic
VBATT _{5.5V ± 22V}
VDDIO reference voltage
VSYNC signal
100 nF
CVLDO _5V
1 éF
VDDIO
VLDO VIN
VSYNC
L1
D1
CIN ^{15 éH}
10 éF
SW
FB
1 éF 120 k#
RISET
RFSET
MCU
Can be left floating
if not used
FILTER
ISET
FSET
SCLK
SDA
PWM
EN
FAULT
LP8550
GNDs
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
10V ± 40V
210 mA ± 400 mA
39 pF
COUT
4.7 éF
LED Efficiency
100
95
VIN = 12V
90
85
VIN = 9V
80
75
70
65
60
0 10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.