SNVSB83B June   2019  – January 2020 LP8867-Q1 , LP8869-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Schematic
    2.     LED Backlight Efficiency
  4. 4 Revision History
  5. 5 Device Comparison Table
  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  Internal LDO Electrical Characteristics
    7. 7.7  Protection Electrical Characteristics
    8. 7.8  Current Sinks Electrical Characteristics
    9. 7.9  PWM Brightness Control Electrical Characteristics
    10. 7.10 Boost and SEPIC Converter Characteristics
    11. 7.11 Logic Interface Characteristics
    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 Integrated DC-DC Converter
        1. 8.3.1.1 DC-DC Converter Parameter Configuration
          1. 8.3.1.1.1 Switching Frequency
          2. 8.3.1.1.2 Spread Spectrum and External SYNC
          3. 8.3.1.1.3 Recommended Component Value and Internal Parameters
          4. 8.3.1.1.4 DC-DC Converter Switching Current Limit
          5. 8.3.1.1.5 DC-DC Converter Light Load Mode
        2. 8.3.1.2 Adaptive Voltage Control
          1. 8.3.1.2.1 Using Two-Divider
          2. 8.3.1.2.2 Using T-Divider
          3. 8.3.1.2.3 Feedback Capacitor
      2. 8.3.2 Internal LDO
      3. 8.3.3 LED Current Sinks
        1. 8.3.3.1 LED Output Configuration
        2. 8.3.3.2 LED Current Setting
        3. 8.3.3.3 Brightness Control
      4. 8.3.4 Power-Line FET Control
      5. 8.3.5 LED Current Dimming With External Temperature Sensor
      6. 8.3.6 Fault Detections and Protection
        1. 8.3.6.1 Supply Fault and Protection
          1. 8.3.6.1.1 VIN Undervoltage Fault (VIN_UVLO)
          2. 8.3.6.1.2 VIN Overvoltage Fault (VIN_OVP)
          3. 8.3.6.1.3 VIN Overcurrent Fault (VIN_OCP)
        2. 8.3.6.2 Boost Fault and Protection
          1. 8.3.6.2.1 Boost Overvoltage Fault (BST_OVP)
          2. 8.3.6.2.2 SW Overvoltage Fault (SW_OVP)
        3. 8.3.6.3 LED Fault and Protection (LED_OPEN and LED_SHORT)
        4. 8.3.6.4 Thermal Fault and Protection (TSD)
        5. 8.3.6.5 Overview of the Fault and Protection Schemes
    4. 8.4 Device Functional Modes
      1. 8.4.1 STANDBY State
      2. 8.4.2 SOFT START State
      3. 8.4.3 BOOST START State
      4. 8.4.4 NORMAL State
      5. 8.4.5 FAULT RECOVERY State
      6. 8.4.6 State Diagram and Timing Diagram for Start-up and Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Typical Application for 4 LED Strings
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detailed Design Procedure
        1. 9.2.3.1 Inductor Selection
        2. 9.2.3.2 Output Capacitor Selection
        3. 9.2.3.3 Input Capacitor Selection
        4. 9.2.3.4 LDO Output Capacitor
        5. 9.2.3.5 Diode
      4. 9.2.4 Application Curves
      5. 9.2.5 SEPIC Mode Application
        1. 9.2.5.1 Design Requirements
        2. 9.2.5.2 Detailed Design Procedure
          1. 9.2.5.2.1 Inductor
          2. 9.2.5.2.2 Diode
          3. 9.2.5.2.3 Capacitor C1
        3. 9.2.5.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.1.2.2 Using T-Divider

Alternatively, a T-divider can be used if resistance less than 100 kΩ is required for the external resistive divider. Then the maximum, minimum and initial boost voltages can be calculated with

Equation 3. LP8867-Q1 LP8869-Q1 eq-01-adaptive-Tres.gif

where

  • VBG = 1.2 V
  • R2 recommended value is 10 kΩ to 200 kΩ
  • R1/R2 recommended value is 5 to 10
  • K = 1 for maximum adaptive boost voltage (typical)
  • K = 0 for minimum adaptive boost voltage (typical)
  • K = 0.88 for initial boost voltage (typical)

For example, if R1 is set to 100 kΩ, R2 is set to 10 kΩ and R3 is set to 60 kΩ, VBOOST will be in the range of 13.2 V to 42.6 V.

LP8867-Q1 LP8869-Q1 fb-03-fb_Tres.gifFigure 12. FB External T-divider Resistors