SNVS657E September   2010  – September 2014 LP8550

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Default Values
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  Handling Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics
    6. 7.6  Boost Converter Electrical Characteristics
    7. 7.7  LED Driver Electrical Characteristics
    8. 7.8  PWM Interface Characteristics
    9. 7.9  Undervoltage Protection
    10. 7.10 Logic Interface Characteristics
    11. 7.11 I2C Serial Bus Timing Parameters (SDA, SCLK)
    12. 7.12 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 Clock Generation
      2. 8.3.2 Brightness Control Methods
        1. 8.3.2.1  PWM Input Duty Cycle
        2. 8.3.2.2  Brightness Register Control
        3. 8.3.2.3  PWM Direct Control
        4. 8.3.2.4  PWM Calculation Data Flow
        5. 8.3.2.5  PWM Detector
        6. 8.3.2.6  Brightness Control
        7. 8.3.2.7  Resolution Selector
        8. 8.3.2.8  Sloper
        9. 8.3.2.9  PWM & Current Control
        10. 8.3.2.10 Dither
        11. 8.3.2.11 PWM Comparator
        12. 8.3.2.12 Current Setting
        13. 8.3.2.13 PWM Frequency Setting
        14. 8.3.2.14 Phase Shift PWM (PSPWM) Scheme
        15. 8.3.2.15 Slope and Dithering
        16. 8.3.2.16 Driver Headroom Control
      3. 8.3.3 Boost Converter
        1. 8.3.3.1 Operation
        2. 8.3.3.2 Protection
        3. 8.3.3.3 Manual Output Voltage Control
        4. 8.3.3.4 Adaptive Boost Control
      4. 8.3.4 Fault Detection
        1. 8.3.4.1 LED Fault Detection
        2. 8.3.4.2 Undervoltage Detection
        3. 8.3.4.3 Overcurrent Protection
        4. 8.3.4.4 Device Thermal Regulation
        5. 8.3.4.5 Thermal Shutdown
    4. 8.4 Device Functional Modes
    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
      2. 8.5.2 EEPROM
    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 Fault
        4. 8.6.1.4 Identification
        5. 8.6.1.5 Direct Control
        6. 8.6.1.6 Temp MSB
        7. 8.6.1.7 Temp LSB
        8. 8.6.1.8 EEPROM Control
      2. 8.6.2 EEPROM Bit Explanations
        1. 8.6.2.1 EEPROM Register Map
        2. 8.6.2.2 EEPROM Address 0
        3. 8.6.2.3 EEPROM Address 1
        4. 8.6.2.4 EEPROM Address 2
        5. 8.6.2.5 EEPROM Address 3
        6. 8.6.2.6 EEPROM Address 4
        7. 8.6.2.7 EEPROM Address 5
        8. 8.6.2.8 EEPROM Address 6
        9. 8.6.2.9 EEPROM Address 7
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Typical Application Using Internal LDO
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Inductor Selection
          2. 9.2.1.2.2 Output Capacitor
          3. 9.2.1.2.3 LDO Capacitor
          4. 9.2.1.2.4 Output Diode
          5. 9.2.1.2.5 Resistors for Setting the LED Current and PWM Frequency
          6. 9.2.1.2.6 Filter Component Values
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Typical Application for Low Input Voltage
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 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 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

1 Features

  • 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

30116370.gif

LED Efficiency

30116310.gif