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

7.3.17 Dual Random Spread Spectrum – DRSS

The device provides a digital spread spectrum, which reduces the EMI of the power supply over a wide frequency range. This function is enabled by the CFG pin. When the spread spectrum is enabled, the internal modulator dithers the internal clock. When an external synchronization clock is applied to the SYNC pin, the internal spread spectrum is disabled. DRSS combines a low frequency triangular modulation profile with a high frequency cycle-by-cycle random modulation profile. The low frequency triangular modulation improves performance in lower radio frequency bands (for example, AM band), while the high frequency random modulation improves performance in higher radio frequency bands (for example, FM band). In addition, the frequency of the triangular modulation is further modulated randomly to reduce the likelihood of any audible tones. To minimize output voltage ripple caused by spread spectrum, duty cycle is modified on a cycle-by-cycle basis to maintain a nearly constant duty cycle when dithering is enabled.


LM5177 Dual Random Spread Spectrum
Figure 7-19 Dual Random Spread Spectrum