ZHCSIN4B August   2018  – June 2021 LM5146-Q1

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 说明（续）
  6. 6 Pin Configuration and Functions
    1. 6.1 Wettable Flanks
  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 Switching Characteristics
    7. 7.7 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  Input Range (VIN)
      2. 8.3.2  Output Voltage Setpoint and Accuracy (FB)
      3. 8.3.3  High-Voltage Bias Supply Regulator (VCC)
      4. 8.3.4  Precision Enable (EN/UVLO)
      5. 8.3.5  Power Good Monitor (PGOOD)
      6. 8.3.6  Switching Frequency (RT, SYNCIN)
        1. 8.3.6.1 Frequency Adjust
        2. 8.3.6.2 Clock Synchronization
      7. 8.3.7  Configurable Soft Start (SS/TRK)
        1. 8.3.7.1 Tracking
      8. 8.3.8  Voltage-Mode Control (COMP)
      9. 8.3.9  Gate Drivers (LO, HO)
      10. 8.3.10 Current Sensing and Overcurrent Protection (ILIM)
      11. 8.3.11 OCP Duty Cycle Limiter
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
      4. 8.4.4 Diode Emulation Mode
      5. 8.4.5 Thermal Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Design and Implementation
      2. 9.1.2 Power Train Components
        1. 9.1.2.1 Inductor
        2. 9.1.2.2 Output Capacitors
        3. 9.1.2.3 Input Capacitors
        4. 9.1.2.4 Power MOSFETs
      3. 9.1.3 Control Loop Compensation
      4. 9.1.4 EMI Filter Design
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 – 12-A High-Efficiency Synchronous Buck DC/DC Regulator for Automotive Applications
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Custom Design With WEBENCH® Tools
        4. 9.2.1.4 Custom Design With Excel Quickstart Tool
        5. 9.2.1.5 Application Curves
      2. 9.2.2 Design 2 – High Density, 12-V, 8-A Rail From 48-V Automotive Battery Power
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Power Stage Layout
      2. 11.1.2 Gate Drive Layout
      3. 11.1.3 PWM Controller Layout
      4. 11.1.4 Thermal Design and Layout
      5. 11.1.5 Ground Plane Design
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 第三方产品免责声明
      2. 12.1.2 Development Support
        1. 12.1.2.1 Custom Design With WEBENCH® Tools
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
        1. 12.2.1.1 PCB Layout Resources
        2. 12.2.1.2 Thermal Design Resources
    3. 12.3 接收文档更新通知
    4. 12.4 支持资源
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • RGY|20
散热焊盘机械数据 (封装 | 引脚)
订购信息

8.3.3 High-Voltage Bias Supply Regulator (VCC)

The LM5146-Q1 contains an internal high-voltage VCC regulator that provides a bias supply for the PWM controller and its gate drivers for the external MOSFETs. The input pin (VIN) can be connected directly to an input voltage source up to 100 V. The output of the VCC regulator is set to 7.5 V. However, when the input voltage is below the VCC setpoint level, the VCC output tracks VIN with a small voltage drop. Connect a ceramic decoupling capacitor between 1 µF and 5 µF from VCC to AGND for stability.

The VCC regulator output has a current limit of 40 mA (minimum). At power up, the regulator sources current into the capacitor connected to the VCC pin. When the VCC voltage exceeds its rising UVLO threshold of 4.93 V, the output is enabled (if EN/UVLO is above 1.2 V), and the soft-start sequence begins. The output remains active until the VCC voltage falls below its falling UVLO threshold of 4.67 V (typical) or if EN/UVLO goes to a standby or shutdown state.

Internal power dissipation of the VCC regulator can be minimized by connecting the output voltage or an auxiliary bias supply rail (up to 13 V) to VCC using a diode DVCC as shown in Figure 8-2. A diode in series with the input prevents reverse current flow from VCC to VIN if the input voltage falls below the external VCC rail.

GUID-213778AD-B764-4EC4-995A-4CD1AC8C6580-low.gifFigure 8-2 VCC Bias Supply Connection From VOUT or Auxiliary Supply

Note that a finite bias supply regulator dropout voltage exists and is manifested to a larger extent when driving high gate charge (QG) power MOSFETs at elevated switching frequencies. For example, at VVIN = 6 V, the VCC voltage is 5.8 V with a DC operating current, IVCC, of 20 mA. Such a low gate drive voltage can be insufficient to fully enhance the power MOSFETs. At the very least, MOSFET on-state resistance, RDS(ON), can increase at such low gate drive voltage.

Here are the main considerations when operating at input voltages below 7.5 V:

  • Increased MOSFET RDS(on) at lower VGS, leading to Increased conduction losses and reduced OCP setpoint
  • Increased switching losses given the slower switching times when operating at lower gate voltages
  • Restricted range of suitable power MOSFETs to choose from (MOSFETs with RDS(on) rated at VGS = 4.5 V become mandatory)