ZHCSK37 August   2019 LP8867C-Q1 , LP8869C-Q1

PRODUCTION DATA.  

  1. 1 特性
    1.     简化原理图
  2. 2 应用
  3. 3 说明
    1.     系统效率
  4. 4 修订历史记录
  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 Protection and Fault Detections
        1. 8.3.4.1 Supply Fault and Protection
          1. 8.3.4.1.1 VIN Undervoltage Fault (VIN_UVLO)
          2. 8.3.4.1.2 VIN Overvoltage Fault (VIN_OVP)
        2. 8.3.4.2 Boost Fault and Protection
          1. 8.3.4.2.1 Boost Overvoltage Fault (BST_OVP)
          2. 8.3.4.2.2 SW Overvoltage Fault (SW_OVP)
        3. 8.3.4.3 LED Fault and Protection
          1. 8.3.4.3.1 LED Open Fault (LED_OPEN)
          2. 8.3.4.3.2 LED Short Fault (LED_SHORT)
        4. 8.3.4.4 Thermal Fault and Protection (TSD)
        5. 8.3.4.5 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
        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 Selection
          3. 9.2.1.2.3 Input Capacitor Selection
          4. 9.2.1.2.4 LDO Output Capacitor
          5. 9.2.1.2.5 Diode
        3. 9.2.1.3 Application Curves
      2. 9.2.2 SEPIC Mode Application
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Inductor
          2. 9.2.2.2.2 Diode
          3. 9.2.2.2.3 Capacitor C1
        3. 9.2.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12器件和文档支持
    1. 12.1 器件支持
      1. 12.1.1 开发支持
    2. 12.2 文档支持
      1. 12.2.1 相关文档
    3. 12.3 接收文档更新通知
    4. 12.4 社区资源
    5. 12.5 商标
    6. 12.6 静电放电警告
    7. 12.7 Glossary
  13. 13机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

8.3.4.2.1 Boost Overvoltage Fault (BST_OVP)

The LP886xC-Q1 device supports boost overvoltage protection. If during LP886xC-Q1 operation, the FB pin voltage exceeds the VFB_OVP threshold, which is 2.3-V typical, the boost, LED outputs and the power-line FET will be turned off, and the device will enter FAULT RECOVERY mode. The FAULT pin will be pulled low. The LP886xC-Q1 will exit FAULT RECOVERY mode after 100 ms and try the start-up sequence again. BST_OVP fault detection is available in NORMAL state.

Calculating back from FB pin voltage threshold to boost output OVP voltage threshold, the value is not a static threshold, but a dynamic threshold changing with the current target boost adaptive voltage:

Equation 6. LP8867C-Q1 LP8869C-Q1 eq-04-BoostOVP.gif

where

  • VBOOST is the current target boost adaptive voltage, which in most time is the current largest LED string forward voltage among multiple strings + 0.9 V in steady state
  • VFB_OVP = 2.3 V
  • VBG = 1.2 V
  • R1 and R2 is the resistor value of FB external network in Using Two-Divider and Using T-Divider

For example, if R1 is set to 750 kΩ and R2 is set to 130 kΩ, VBOOST will report OVP when the boost voltage is 7.4 V above target boost voltage.

This equation holds true in both two-divider FB external network and T-divider FB external network.
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