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  • LP8556 High-Efficiency LED Backlight Driver For Tablets

    • SNVS871M July   2012  – June 2020 LP8556

      PRODUCTION DATA.  

  • CONTENTS
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  • LP8556 High-Efficiency LED Backlight Driver For Tablets
  1. 1 Features
  2. 2 Applications
    1.     Simplified Schematic
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Options
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics
    6. 7.6  Electrical Characteristics — Boost Converter
    7. 7.7  Electrical Characteristics — LED Driver
    8. 7.8  Electrical Characteristics — PWM Interface
    9. 7.9  Electrical Characteristics — Logic Interface
    10. 7.10 I2C Serial Bus Timing Parameters (SDA, SCL)
    11. 7.11 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Boost Converter
        1. 8.3.1.1 Boost Converter Operation
        2. 8.3.1.2 Setting Boost Switching Frequency
        3. 8.3.1.3 Output Voltage Control
          1. 8.3.1.3.1 Adaptive Control
          2. 8.3.1.3.2 Manual Control
        4. 8.3.1.4 EMI Reduction
      2. 8.3.2 Brightness Control
        1. 8.3.2.1  BRT_MODE = 00
        2. 8.3.2.2  BRT_MODE = 01
        3. 8.3.2.3  BRT_MODE = 10
        4. 8.3.2.4  BRT_MODE = 11
        5. 8.3.2.5  Output Dimming Schemes
          1. 8.3.2.5.1 PWM Control
          2. 8.3.2.5.2 Pure Current Control
          3. 8.3.2.5.3 Adaptive Control
        6. 8.3.2.6  Setting Full-Scale LED Current
        7. 8.3.2.7  Setting PWM Dimming Frequency
        8. 8.3.2.8  Phase Shift PWM Scheme
        9. 8.3.2.9  Slope and Advanced Slope
        10. 8.3.2.10 Dithering
      3. 8.3.3 Fault Detection
        1. 8.3.3.1 LED Fault Detection
          1. 8.3.3.1.1 Open Detect
          2. 8.3.3.1.2 Short Detect
        2. 8.3.3.2 Undervoltage Detection
        3. 8.3.3.3 Overcurrent Protection
        4. 8.3.3.4 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Active Mode
    5. 8.5 Programming
      1. 8.5.1 I2C-Compatible Serial Bus Interface
        1. 8.5.1.1 Interface Bus Overview
        2. 8.5.1.2 Data Transactions
        3. 8.5.1.3 Acknowledge Cycle
        4. 8.5.1.4 Acknowledge After Every Byte Rule
        5. 8.5.1.5 Addressing Transfer Formats
        6. 8.5.1.6 Control Register Write Cycle
        7. 8.5.1.7 Control Register Read Cycle
        8. 8.5.1.8 Register Read and Write Detail
    6. 8.6 Register Maps
      1. 8.6.1 Register Bit Explanations
        1. 8.6.1.1 Brightness Control
        2. 8.6.1.2 Device Control
        3. 8.6.1.3 Status
        4. 8.6.1.4 Direct Control
        5. 8.6.1.5 LED String Enable
      2. 8.6.2 EPROM Bit Explanations
        1. 8.6.2.1  LP8556TM (DSBGA) Configurations and Pre-Configured EPROM Settings
        2. 8.6.2.2  LP8556TM (DSBGA) Configurations and Pre-configured EPROM Settings Continued
        3. 8.6.2.3  LP8556SQ (WQFN) Configurations and Pre-configured EPROM Settings
        4. 8.6.2.4  CFG98
        5. 8.6.2.5  CFG9E
        6. 8.6.2.6  CFG0
        7. 8.6.2.7  CFG1
        8. 8.6.2.8  CFG2
        9. 8.6.2.9  CFG3
        10. 8.6.2.10 CFG4
        11. 8.6.2.11 CFG5
        12. 8.6.2.12 CFG6
        13. 8.6.2.13 CFG7
        14. 8.6.2.14 CFG9
        15. 8.6.2.15 CFGA
        16. 8.6.2.16 CFGE
        17. 8.6.2.17 CFGF
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Using LP8556 With I2C Host
        1. 9.1.1.1 Setting Boost Switching and PWM Dimming Frequencies
        2. 9.1.1.2 Setting Full-Scale LED Current
      2. 9.1.2 Using LP8556 With Configuration Resistors and IO Pins
        1. 9.1.2.1 Setting Boost Switching and PWM Dimming Frequencies
        2. 9.1.2.2 Setting Full-Scale LED Current
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Recommended Inductance for the Boost Power Stage
        2. 9.2.2.2 Recommended Capacitances for the Boost and LDO Power Stages
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information
  14. IMPORTANT NOTICE
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DATA SHEET

LP8556 High-Efficiency LED Backlight Driver For Tablets

1 Features

  • High-efficiency DC/DC boost converter with integrated 0.19-Ω power MOSFET and three switching frequency options: 312 kHz, 625 kHz, and 1250 kHz
  • 2.7-V to 36-V Boost switch input voltage range supports multi-cell Li-Ion batteries
    (2.7-V to 20-V VDD input range)
  • 7-V to 43-V Boost switch output voltage range supports as few as 3 WLEDs in series per channel and as many as 12
  • Configurable channel count (1 to 6)
  • Up to 50 mA per channel
  • PWM and / or I2C brightness control
  • Phase-shift PWM mode reduces audible noise
  • Adaptive dimming for higher LED drive optical efficiency
  • Programmable edge-rate control and spread spectrum scheme minimize switching noise and improve EMI performance
  • LED fault (short and open) detection, UVLO, TSD, OCP, and OVP (up to 6 threshold options)
  • Available in tiny 20-pin, 0.4-mm pitch DSBGA package and 24-pin, 0.5-mm pitch WQFN package

2 Applications

    LED backlights for tablet LCDs

    space

Simplified Schematic

LP8556 30162637.gif

3 Description

The LP8556 device is a white-LED driver featuring an asynchronous boost converter and six high precision current sinks that can be controlled by a PWM signal or an I2C master.

The boost converter uses adaptive output voltage control for setting the optimal LED driver voltages as low as 7 V and as high as 43 V. This feature minimizes the power consumption by adjusting the output voltage to the lowest sufficient level under all conditions. The converter can operate at three switching frequencies: 312 kHz, 625 kHz, and 1250 kHz, which can be set with an external resistor or pre-configured via EPROM. Programmable slew rate control and spread spectrum scheme minimize switching noise and improve EMI performance.

LED current sinks can be set with the PWM dimming resolution of up to 15 bits. Proprietary adaptive dimming mode allows higher system power saving. In addition, phase shifted LED PWM dimming allows reduced audible noise and smaller boost output capacitors.

The LP8556 device has a full set of fault-protection features that ensure robust operation of the device and external components. The set consists of input undervoltage lockout (UVLO), thermal shutdown (TSD), overcurrent protection (OCP), up to 6 levels of overvoltage protection (OVP), LED open and short detection.

The LP8556 device operates over the ambient temperature range of –30°C to +85°C. It is available in space-saving 20-pin DSBGA and 24-pad WQFN packages.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE
LP8556 DSBGA (20) 2.401 mm × 1.74 mm (MAX)
WQFN (24) 4.00 mm × 4.00 mm (NOM)
  1. For all available packages, see the orderable addendum at the end of the data sheet.

4 Revision History

Changes from L Revision (May 2019) to M Revision

  • Changed Description statement for clarification at Register CFG9EGo

Changes from K Revision (March 2019) to L Revision

  • Deleted 03H register from Table 9Go
  • Deleted 8.6.1.4 Identification section from the Register Bit ExplanationsGo

Changes from J Revision (January 2018) to K Revision

  • Added separate ESD Rating for the WQFN package - changed from "±2000" to "±1000"Go

Changes from I Revision (March 2016) to J Revision

  • Added content in VBOOST_RANGE description of CFG9EGo

Changes from H Revision (December 2014) to I Revision

  • Changed "25 mA" to "23 mA" - E00, E08 and E09 SQ rows, E09, E11 TME rowsGo
  • Changed Handing Ratings table to ESD RatingsGo
  • Added updated Thermal InformationGo
  • Changed "8" to "10" in PWMres rowGo
  • Changed subtracted 1 from bit value of all Table 4 "ƒPWM [Hz] (Resolution)" entries Go
  • Changed subtracted 1 from bit value of all Table 5 "ƒPWM [Hz] (Resolution)" entries except 2402 Go
  • Changed subtracted 1 from bit value of all Table 11 "ƒPWM [Hz] (Resolution)" entries Go
  • Changed "via EPROM" in Table 13 title to "With an External Resistor" Go
  • Changed subtracted 1 from bit values of all Table 13 "ƒPWM [Hz] (Resolution)" entries except 2402 Go

Changes from G Revision (November 2013) to H Revision

  • Added Pin Configuration and Functions section, Handling Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section Go

Changes from E Revision (August 2013) to G Revision

  • Changed Description of "1=" for OCP row in Fault table, STATUS Register SectionGo
  • Changed A7h values for E02, E03, E04, E06, E07, E09, E11 DSGBA EPROM Bit Explanations tablesGo
  • Deleted E00, E01, E08, E10, E12, E13 columns and A8H row from 3 EPROM Bit Explanations tableGo
  • Changed values for E00, E08, E09 WQFN EPROM Settings tableGo

 
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