LP8555 Datasheet, PDF (1/64 Pages) Texas Instruments – LP8555 High-Efficiency LED Backlight Driver for Tablet PCs

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LP8555
SNVS857 – FEBRUARY 2014
LP8555 High-Efficiency LED Backlight Driver for Tablet PCs
1 Features
•1 Dual High-Efficiency DC/DC Boost Converters
• 2.7-V to 20-V VDD Range
• 12 50-mA High-Precision LED Current Sinks With
12-Bit Brightness Control
• Adaptive LED Current Sink Headroom Controls for
Maximum System Efficiency
• LED String Count Auto-Detection
• Phase-Shifted PWM Mode for Reduced Audible
Noise
• PWM Input Duty-Cycle and/or I²C-Register
Brightness Control
• Hybrid PWM and Current Dimming for Higher LED
Drive Optical Efficiency
• Flexible CABC Support
• EPROM, I²C-Register, or External Resistors for
Configuration
• Improved Boost EMI Performance with Slew-Rate
Control, Spread Spectrum, and Phase-Shifted
Switching
• Extensive Fault Detection Schemes
2 Applications
• Tablet LCD Display LED Backlight
3 Description
The LP8555 is a high efficiency LED driver with
integrated dual DC-DC boost converters. It has 12
high-precision current sinks that can be controlled by
a PWM input signal, an I²C master, or both.
Dual-boost configuration of LP8555 shares the load
to two inductors and allows thinner overall solution
size and better efficiency compared to single-boost
solutions. 12 LED strings allows driving high number
of LEDs with optimal efficiency since boost
conversion ratio can be kept low.
The boost converter has adaptive output voltage
control based on the LED current sink headroom
voltages. This feature minimizes the power
consumption by adjusting the voltage to lowest
sufficient level in all conditions.
The LED string auto-detect function enables use of
the same device in systems with 2 to 12 LED strings
for the maximum design flexibility. Proprietary Hybrid
PWM and Current dimming mode enables additional
system power savings. Phase-shift PWM allows
reduced audible noise and smaller boost output
capacitors. Flexible CABC support combines
brightness level selections based on the PWM input
and I²C commands.
Device Information
ORDER NUMBER PACKAGE
BODY SIZE
LP8555YFQR
DSBGA (36)
2,478mm x 2,478mm
4 Simplified Schematic
VBATT
2.7V ± 20V
CVDD
L1
D1
CIN_A
CVLDO
VDD
VLDO
SW_A
FB_A
EN
SDA
RPULL-UP
SCL
INT
VDDIO
RPULL-UP
LP8555
EN/VDDIO
FSET/SDA
LEDA1
LEDA2
LEDA3
LEDA4
LEDA5
LEDA6
ISET/SCL
PWM/INT
LEDB1
LEDB2
LEDB3
LEDB4
LEDB5
LEDB6
GNDs
FB_B
SW_B
VBATT
2.7V ± 20V
CIN_B
L2
D2
7 - 28V
1.3 ”9OUT / VIN ”10
COUT_A
VOUT_A
LCD Display
VOUT_B
COUT_B
7 - 28V
1.3 ”9OUT / VIN ”10
LED Drive Efficiency
92
Inductor: IHLP2525CZER6R8M01
90
88
86
84
82
80
0
VIN = 3.0 V
VIN = 3.7 V
VIN = 4.2 V
VIN = 5.4 V
VIN = 7.4 V
VIN = 8.4 V
20
40
60
80
100
Brightness (%)
C002
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.