SNVS857 February   2014 LP8555

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Terminal 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 I2C Serial Bus Timing Parameters (FSET/SDA, ISET/SCL)
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Features Description
      1. 8.3.1 Boost Converter Overview
        1. 8.3.1.1 Operation
        2. 8.3.1.2 Protection
        3. 8.3.1.3 Setting Boost Switching Frequency
        4. 8.3.1.4 Adaptive Boost Output Voltage Control
        5. 8.3.1.5 EMI Reduction
      2. 8.3.2 Brightness Control
        1. 8.3.2.1 PWM Input Duty Measurement
        2. 8.3.2.2 BRTMODE = 00
        3. 8.3.2.3 BRTMODE = 01
        4. 8.3.2.4 BRTMODE = 10
        5. 8.3.2.5 BRTMODE = 11
        6. 8.3.2.6 Hybrid PWM and Current Dimming Control
        7. 8.3.2.7 Setting PWM Dimming Frequency
        8. 8.3.2.8 Setting Full-Scale LED Current
        9. 8.3.2.9 Phase-Shift PWM Scheme
      3. 8.3.3 LED Brightness Slopes, Normal and Advanced
      4. 8.3.4 Start-up and Shutdown Sequences
        1. 8.3.4.1 Start-up With PWM Input Brightness Control Mode (BRTMODE = 00b)
        2. 8.3.4.2 Shutdown With PWM Input Brightness Control Mode (BRTMODE = 00b)
        3. 8.3.4.3 Start-up With I2C Brightness Control Mode (BRTMODE = 01b)
        4. 8.3.4.4 Shutdown With I2C Brightness Control Mode (BRTMODE = 01b)
        5. 8.3.4.5 Start-up with I2C + PWM Input Brightness Control Mode (BRTMODE = 10 or 11b)
        6. 8.3.4.6 Shutdown with I2C + PWM Input Brightness Control Mode (BRTMODE = 10 or 11b)
      5. 8.3.5 LED String Count Auto Detection
      6. 8.3.6 Fault Detection
        1. 8.3.6.1 LED Short Detection
        2. 8.3.6.2 LED Open Detection
        3. 8.3.6.3 Undervoltage Detection
        4. 8.3.6.4 Thermal Shutdown
        5. 8.3.6.5 Boost Overcurrent Protection
        6. 8.3.6.6 Boost Overvoltage Protection
        7. 8.3.6.7 Boost Undervoltage Protection
      7. 8.3.7 I2C-Compatible Serial Bus Interface
        1. 8.3.7.1 Interface Bus Overview
        2. 8.3.7.2 Data Transactions
        3. 8.3.7.3 Acknowledge Cycle
        4. 8.3.7.4 “Acknowledge After Every Byte” Rule
        5. 8.3.7.5 Addressing Transfer Formats
        6. 8.3.7.6 Control Register Write Cycle
        7. 8.3.7.7 Control Register Read Cycle
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operation Without I2C Control
      2. 8.4.2 Operation With I2C Control
      3. 8.4.3 Shutdown Mode
      4. 8.4.4 Standby Mode
      5. 8.4.5 Active Mode
    5. 8.5 Register Maps
      1. 8.5.1  COMMAND
      2. 8.5.2  STATUS/MASK
      3. 8.5.3  BRTLO
      4. 8.5.4  BTHI
      5. 8.5.5  CONFIG
      6. 8.5.6  CURRENT
      7. 8.5.7  PGEN
      8. 8.5.8  BOOST
      9. 8.5.9  LEDEN
      10. 8.5.10 STEP
      11. 8.5.11 Brightness Transitions, Typical Times
      12. 8.5.12 VOLTAGE_0
      13. 8.5.13 LEDEN1
      14. 8.5.14 VOLTAGE1
      15. 8.5.15 OPTION
      16. 8.5.16 EXTRA
      17. 8.5.17 ID
      18. 8.5.18 REVISION
      19. 8.5.19 CONF0
      20. 8.5.20 CONF1
      21. 8.5.21 VHR0
      22. 8.5.22 VHR1
      23. 8.5.23 JUMP
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Application for Default LP8555YFQR EPROM Configuration
        1. 9.2.1.1 Schematic
        2. 9.2.1.2 LP8555YFQR EPROM Configuration
        3. 9.2.1.3 Design Requirements
        4. 9.2.1.4 Detailed Design Procedure
          1. 9.2.1.4.1 Inductor
          2. 9.2.1.4.2 Output Capacitor
          3. 9.2.1.4.3 LDO Capacitor
          4. 9.2.1.4.4 VDD Capacitor
          5. 9.2.1.4.5 Boost Input Capacitor
          6. 9.2.1.4.6 Diode
        5. 9.2.1.5 Application Performance Plots
      2. 9.2.2 Application Example With Different LED Configuration for Each Bank
        1. 9.2.2.1 Schematic
      3. 9.2.3 Application Example With 12 LED Strings and PWM Input Brightness Control
        1. 9.2.3.1 Schematic
      4. 9.2.4 Application With 12 LED Strings, I2C Brightness Control
        1. 9.2.4.1 Schematic
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12 Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

10 Power Supply Recommendations

The device is designed to operate from an input voltage supply range between 2.7 V and 20 V. This input supply should be well regulated and able to withstand maximum input current and maintain stable voltage without voltage drop even at load transition condition (start-up or rapid brightness change). The resistance of the input supply rail should be low enough that the input current transient does not cause drop high enough in the LP8555 supply voltage that can cause false UVLO fault triggering.

If the input supply is located more than a few inches from the LP8555 additional bulk capacitance may be required in addition to the ceramic bypass capacitors. Depending on device EPROM configuration and usage case the boost converter is configured to operate optimally with certain input voltage range. Examples are seen in the Detailed Design Procedures. In uncertain cases, it is recommended to contact TI Sales Representative for confirmation of the compatibility of the use case, EPROM configuration and input voltage range.