ZHCSPC5 October   2022 LM51231-Q1

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Device Enable/Disable (EN, VH Pin)
      2. 7.3.2  High Voltage VCC Regulator (BIAS, VCC Pin)
      3. 7.3.3  Light Load Switching Mode Selection (MODE Pin)
      4. 7.3.4  VOUT Range Selection (RANGE Pin)
      5. 7.3.5  Line Undervoltage Lockout (UVLO Pin)
      6. 7.3.6  Fast Restart using VCC HOLD (VH Pin)
      7. 7.3.7  Adjustable Output Regulation Target (VOUT, TRK, VREF Pin)
      8. 7.3.8  Overvoltage Protection (VOUT Pin)
      9. 7.3.9  Power Good Indicator (PGOOD Pin)
      10. 7.3.10 Dynamically Programmable Switching Frequency (RT)
      11. 7.3.11 External Clock Synchronization (SYNC Pin)
      12. 7.3.12 Programmable Spread Spectrum (DITHER Pin)
      13. 7.3.13 Programmable Soft-start (SS Pin)
      14. 7.3.14 Wide Bandwidth Transconductance Error Amplifier and PWM (TRK, COMP Pin)
      15. 7.3.15 Current Sensing and Slope Compensation (CSP, CSN Pin)
      16. 7.3.16 Constant Peak Current Limit (CSP, CSN Pin)
      17. 7.3.17 Maximum Duty Cycle and Minimum Controllable On-time Limits
      18. 7.3.18 MOSFET Drivers, Integrated Boot Diode, and Hiccup Mode Fault Protection (LO, HO, HB Pin)
      19. 7.3.19 Thermal Shutdown Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Device Status
        1. 7.4.1.1 Shutdown Mode
        2. 7.4.1.2 Configuration Mode
        3. 7.4.1.3 Active Mode
        4. 7.4.1.4 Bypass Mode
          1. 7.4.1.4.1 Bypass DE mode
          2. 7.4.1.4.2 Bypass FPWM
      2. 7.4.2 Light Load Switching Mode
        1. 7.4.2.1 Forced PWM (FPWM) Mode
        2. 7.4.2.2 Diode Emulation (DE) Mode
        3. 7.4.2.3 Forced Diode Emulation Operation in FPWM Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Ideas
      4. 8.2.4 Application Curves
    3. 8.3 System Example
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  9. 9 Device and Documentation Support
    1. 9.1 接收文档更新通知
    2. 9.2 支持资源
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 术语表
  10. 10Mechanical, Packaging, and Orderable Information

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机械数据 (封装 | 引脚)
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7.3.1 Device Enable/Disable (EN, VH Pin)

The device shuts down when EN is less than the EN threshold (VEN) and VH is less than the SYNC threshold (VSYNC). The device is enabled when EN is greater than VEN or VH is greater than VSYNC. The VH pin provides a 40-μs internal delay before the device shuts down.

The device provides a 33-kΩ internal EN pulldown resistor to prevent a false turnon when the pin is floating. The EN pulldown resistor is connected to ground during the device configuration time or when the device shuts down. If the device configuration is finished and VH is greater than VSYNC, EN hysteresis is accomplished by disconnecting/connecting the resistor when EN is greater/less than VEN.

GUID-B8C08A2F-187D-4488-9408-C4C40055CA53-low.gifFigure 7-1 EN/UVLO Circuit
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