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LP85571 Datasheet

High-Efficiency LED Backlight Driver

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LP8557, LP85571
SNVSA15B – DECEMBER 2013 – REVISED DECEMBER 2015
LP8557 High-Efficiency LED Backlight Driver For Tablets
1 Features
1 High-Efficiency DC-DC Boost Converter With 28-V
Integrated Power MOSFET
• 2.7-V to 5.5-V VDD Range for Supporting Single-
Cell Li-Ion Battery Applications
• Six 25-mA High-Precision LED Current Sinks
• Adaptive Boost Voltage and LED Current Sink
Headroom Controls for Maximum System
Efficiency
• LED String Count Auto-Detect for Maximum
Design Flexibility
• Smart Phase Shift PWM Mode for Reduced
Audible Noise
• PWM Input Duty Cycle Brightness Control, PWM
Output Frequency Selectable Independent of
Input Frequency
• Hybrid PWM Plus Current Dimming for Higher
LED Drive Optical Efficiency
• Switching Frequency, PWM Output Frequency,
and LED Current can be set Through Resistors or
I2C Interface
• Programmable Boost SW Slew Rate Control and
Spread Spectrum Scheme for Reduced Switching
Noise and Improved EMI Performance
• UVLO, TSD, BST_OVP, BST_OCP, BST_UV,
LED OPEN* and LED Short Fault Coverage
• Minimum Number of External Components
2 Applications
Tablet LCD Display LED Backlight
3 Description
The LP8557 and LP8557I are high-efficiency LED
drivers each featuring an integrated DC-DC inductive
boost converter and six high-precision current sinks.
LP8557 is intended for applications that exclusively
use a pulse width modulated (PWM) signal for
controlling the brightness while LP8557I is intended
for applications that can utilize an I2C master as well.
The boost converter has adaptive output voltage
control. This feature minimizes the power
consumption by adjusting the voltage to the lowest
sufficient level under all conditions.
The adaptive current sink headroom voltage control
scales the headroom voltage with the LED current for
optimal system efficiency.
The LED string auto-detect function enables use of
the same device in systems with 1 to 6 LED strings
for the maximum design flexibility.
Proprietary hybrid PWM plus current mode dimming
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(1)
PART NUMBER
PACKAGE
BODY SIZE (MAX)
LP8557
LP8557I
DSBGA (16)
1.906 mm x 1.64 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic With PWM-Only Option
2.7 V ± 5.5 V
VIN
CIN
7 V ± 28 V
L1 D1 1.1 VOUT / VIN 11
VOUT
COU
T
VDD
SW
LED Efficiency With 6 LED Strings
90
88
PWM
PWM
FB
RFSET
RISET
LED1
LED2
LP8557 LED3
FSET
ISET
LED4
LED5
LED6
GNDs
86
84
82
80
0
6p8s
6p6s
6p4s
20 40 60 80 100
Brightness [%]
C001
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.




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LP85571 Datasheet Preview

LP85571 Datasheet

High-Efficiency LED Backlight Driver

No Preview Available !

LP8557, LP85571
SNVSA15B – DECEMBER 2013 – REVISED DECEMBER 2015
www.ti.com
Table of Contents
1 Features .................................................................. 1
2 Applications ........................................................... 1
3 Description ............................................................. 1
4 Revision History..................................................... 2
5 Device Comparison Table..................................... 3
6 Pin Function and Configurations ......................... 3
7 Specifications......................................................... 4
7.1 Absolute Maximum Ratings ...................................... 4
7.2 ESD Ratings.............................................................. 4
7.3 Recommended Operating Conditions....................... 4
7.4 Thermal Information .................................................. 4
7.5 Electrical Characteristics........................................... 5
7.6 Boost Converter Electrical Characteristics................ 5
7.7 LED Driver Electrical Characteristics (LED1 To LED6
Pins) ........................................................................... 5
7.8 PWM Interface Characteristics (PWM Pin) ............... 6
7.9 Logic Interface Characteristics
(PWM, FSET/SDA, ISET/SCL Pins) .......................... 6
7.10 I2C Serial Bus Timing Parameters (SDA, SCL) ..... 7
7.11 Typical Characteristics ............................................ 8
8 Detailed Description ............................................ 11
8.1 Overview ................................................................. 11
8.2 Functional Block Diagram ....................................... 11
8.3 Feature Description................................................. 12
8.4 Device Functional Modes........................................ 20
8.5 Programming........................................................... 20
8.6 Register Maps ......................................................... 24
9 Application and Implementation ........................ 31
9.1 Application Information............................................ 31
9.2 Typical Applications ............................................... 34
10 Power Supply Recommendations ..................... 38
11 Layout................................................................... 38
11.1 Layout Guidelines ................................................. 38
11.2 Layout Example .................................................... 42
12 Device and Documentation Support ................. 43
12.1 Device Support .................................................... 43
12.2 Related Links ........................................................ 43
12.3 Community Resources.......................................... 43
12.4 Trademarks ........................................................... 43
12.5 Electrostatic Discharge Caution ............................ 43
12.6 Glossary ................................................................ 43
13 Mechanical, Packaging, and Orderable
Information ........................................................... 43
4 Revision History
Changes from Revision A (June 2014) to Revision B
Page
• moved storage temperature range to Abs Max table ............................................................................................................ 4
• Changed Handling Ratings table to ESD Ratings table ........................................................................................................ 4
• Updated Thermal Information table ....................................................................................................................................... 4
• Changed word "safety" to "fault detection" ........................................................................................................................... 11
• Deleted "to 25% of the brightness range" ........................................................................................................................... 16
• Changed PGEN register table and descriptions .................................................................................................................. 28
• Changed fixed typo "2.4.4 kHz" to "24.4 kHz" ..................................................................................................................... 28
• Added note to beginning of Application and Implementation section .................................................................................. 31
• Added Community Resources section ................................................................................................................................ 43
Changes from Original (December 2013) to Revision A
Page
• Changed formatting to match new TI datasheet guidelines; added Device Information and Handling Ratings table,
Layout, and Device and Documentation Support sections; reformatted Detailed Description and Application and
Implementation sections, fix typographical errors. ................................................................................................................ 1
• Changed 6 LED strings to 5 LED Strings to correct typo....................................................................................................... 8
• Added PWM Input Duty Measurement subsection............................................................................................................... 13
• Changed description for "0" BFSET as well as description of register table for BFSET bit ................................................ 29
2 Submit Documentation Feedback
Copyright © 2013–2015, Texas Instruments Incorporated
Product Folder Links: LP8557 LP85571


Part Number LP85571
Description High-Efficiency LED Backlight Driver
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