ZHCSE16C July   2015  – November 2017 LM43600-Q1

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
    1.     辐射发射图（VIN = 12V，VOUT = 3.3V FS = 500kHz，IOUT = 0.5A）
  3. 3 说明
    1.     简化原理图
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 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  Fixed Frequency Peak Current Mode Controlled Step-Down Regulator
      2. 7.3.2  Light Load Operation
      3. 7.3.3  Adjustable Output Voltage
      4. 7.3.4  Enable (ENABLE)
      5. 7.3.5  VCC, UVLO and BIAS
      6. 7.3.6  Soft-Start and Voltage Tracking (SS/TRK)
      7. 7.3.7  Switching Frequency (RT) and Synchronization (SYNC)
      8. 7.3.8  Minimum ON-Time, Minimum OFF-Time and Frequency Foldback at Dropout Conditions
      9. 7.3.9  Internal Compensation and CFF
      10. 7.3.10 Bootstrap Voltage (BOOT)
      11. 7.3.11 Power Good (PGOOD)
      12. 7.3.12 Overcurrent and Short-Circuit Protection
      13. 7.3.13 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Stand-by Mode
      3. 7.4.3 Active Mode
      4. 7.4.4 CCM Mode
      5. 7.4.5 Light Load Operation
      6. 7.4.6 Self-Bias Mode
  8. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Custom Design With WEBENCH® Tools
        2. 8.2.2.2  Output Voltage Setpoint
        3. 8.2.2.3  Switching Frequency
        4. 8.2.2.4  Input Capacitors
        5. 8.2.2.5  Inductor Selection
        6. 8.2.2.6  Output Capacitor Selection
        7. 8.2.2.7  Feedvorward Capacitor
        8. 8.2.2.8  Bootstrap Capacitors
        9. 8.2.2.9  VCC Capacitor
        10. 8.2.2.10 BIAS Capacitors
        11. 8.2.2.11 Soft-Start Capacitors
        12. 8.2.2.12 Undervoltage Lockout Setpoint
        13. 8.2.2.13 PGOOD
      3. 8.2.3 Application Performance Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Compact Layout for EMI Reduction
      2. 10.1.2 Ground Plane and Thermal Considerations
      3. 10.1.3 Feedback Resistors
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 开发支持
      1. 11.1.1 使用 WEBENCH® 工具创建定制设计
    2. 11.2 接收文档更新通知
    3. 11.3 社区资源
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 Glossary
  12. 12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

7.3.5 VCC, UVLO and BIAS

The LM43600-Q1 integrates an internal LDO to generate VCC for control circuitry and MOSFET drivers. The nominal voltage for VCC is 3.3 V. The VCC pin is the output of the LDO and must be properly bypassed. A high quality ceramic capacitor with 2.2 µF to 10 µF capacitance and 6.3 V or higher rated voltage should be placed as close as possible to VCC and grounded to the exposed PAD and ground pins. The VCC output pin should not be loaded, left floating, or shorted to ground during operation. Shorting VCC to ground during operation may cause damage to the LM43600-Q1.

Undervoltage lockout (UVLO) prevents the LM43600-Q1 from operating until the VCC voltage exceeds 3.14 V (typical). The VCC UVLO threshold has 567 mV of hysteresis (typically) to prevent undesired shuting down due to temperary VIN droops.

The internal LDO has two inputs: primary from VIN and secondary from BIAS input. The BIAS input powers the LDO when VBIAS is higher than the change-over threshold. Power loss of an LDO is calculated by ILDO * (VIN-LDO - VOUT-LDO). The higher the difference between the input and output voltages of the LDO, the more power loss occur to supply the same output current. The BIAS input is designed to reduce the difference of the input and output voltages of the LDO to reduce power loss and improve LM43600-Q1 efficiency, especially at light load. It is recommended to tie the BIAS pin to VOUT when VOUT ≥ 3.3V. The BIAS pin should be grounded in applications with VOUT less than 3.3 V. BIAS input can also come from an external voltage source, if available, to reduce power loss. When used, a 1µF to 10µF high quality ceramic capacitor is recommended to bypass the BIAS pin to ground.