JAJSOR1E June   2022  – August 2024 LM5177

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Handling Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Parameter Measurement Information
    1. 6.1 Gate Driver Rise Time and Fall Time
    2. 6.2 Gate Driver Dead (Transition) Time
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Power-On Reset (POR System)
      2. 7.3.2  Buck-Boost Control Scheme
        1. 7.3.2.1 Boost Mode
        2. 7.3.2.2 Buck Mode
        3. 7.3.2.3 Buck-Boost Mode
      3. 7.3.3  Power Save Mode
      4. 7.3.4  Supply Voltage Selection – VMAX Switch
      5. 7.3.5  Enable and Undervoltage Lockout
      6. 7.3.6  Oscillator Frequency Selection
      7. 7.3.7  Frequency Synchronization
      8. 7.3.8  Voltage Regulation Loop
      9. 7.3.9  Output Voltage Tracking
      10. 7.3.10 Slope Compensation
      11. 7.3.11 Configurable Soft Start
      12. 7.3.12 Peak Current Sensor
      13. 7.3.13 Current Monitoring and Current Limit Control Loop
      14. 7.3.14 Short Circuit - Hiccup Protection
      15. 7.3.15 nFLT Pin and Protections
      16. 7.3.16 Device Configuration Pin
      17. 7.3.17 Dual Random Spread Spectrum – DRSS
      18. 7.3.18 Gate Driver
    4. 7.4 Device Functional Modes
  9. 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
        1. 8.2.2.1  Custom Design with WEBENCH Tools
        2. 8.2.2.2  Frequency
        3. 8.2.2.3  Feedback Divider
        4. 8.2.2.4  Inductor and Current Sense Resistor Selection
        5. 8.2.2.5  Slope Compensation
        6. 8.2.2.6  Output Capacitor
        7. 8.2.2.7  Input Capacitor
        8. 8.2.2.8  UVLO Divider
        9. 8.2.2.9  Soft-Start Capacitor
        10. 8.2.2.10 MOSFETs QH1 and QL1
        11. 8.2.2.11 MOSFETs QH2 and QL2
        12. 8.2.2.12 Frequency Compensation
        13. 8.2.2.13 External Component Selection
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
      1. 8.3.1 Bi-Directional Power Backup
      2. 8.3.2 Parallel (Multiphase) Operation
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Power Stage Layout
      2. 10.1.2 Gate Driver Layout
      3. 10.1.3 Controller Layout
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 サード・パーティ製品に関する免責事項
      2. 11.1.2 Development Support
        1. 11.1.2.1 Custom Design with WEBENCH Tools
    2. 11.2 ドキュメントの更新通知を受け取る方法
    3. 11.3 サポート・リソース
    4. 11.4 Trademarks
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 用語集
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

7.3.4 Supply Voltage Selection – VMAX Switch

There are two pins to supply the LM5177 internal voltage regulators. Due to the internal supply voltage selection circuit, the device can reduce the power dissipation through a seamless operation at low input or output voltages as well as in transient operating conditions like an output short. The VMAX switch selects the pin with the lower voltage from the VIN or BIAS pin once the voltage on both is above the switch-over threshold (VT(VCC, SUP)). If one pin voltage is lower than the threshold, the other supply pin is selected. And if both pins are lower than the switch-over threshold, the higher voltage of VIN or BIAS is selected as supply. The following are common configurations for the supply pins:

  • The VIN pin is connected to the supply voltage. The BIAS pin is connected to VO. During start-up, that is as long as the output voltage is not higher than the supply switch-over threshold, the VIN supplies the internal regulators. Once VO is high enough, the supply current comes from the BIAS pin.
  • Both the VIN pin and the BIAS pin are connected together to the input supply voltage. This configuration is often used in applications where the input supply voltage is usually lower or equal than the output voltage. As the BIAS pin is connected to the input voltage, the device has the full current capability of the internal regulators at low input voltages for start-up.
  • The VIN is connected to the input supply voltage and the BIAS pin is connected to an auxiliary supply (for example, an existing 12V DC/DC converter). This configuration is commonly used at high voltage applications on the input and output voltages where the power dissipation over the integrated linear regulators must be further minimized.

LM5177 VMAX Supply Scenario 1

Figure 7-6 VMAX Supply Scenario 1
LM5177 VMAX Supply Scenario 2 Figure 7-7 VMAX Supply Scenario 2

LM5177 VMAX Supply Scenario 3

Figure 7-8 VMAX Supply Scenario 3