ZHCSLO7B December   2020  – January 2023 LM25149-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 Active EMI Filter
    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 Voltage Range (VIN)
      2. 8.3.2  High-Voltage Bias Supply Regulator (VCC, VCCX, VDDA)
      3. 8.3.3  Precision Enable (EN)
      4. 8.3.4  Power-Good Monitor (PG)
      5. 8.3.5  Switching Frequency (RT)
      6. 8.3.6  Active EMI Filter
      7. 8.3.7  Dual Random Spread Spectrum (DRSS)
      8. 8.3.8  Soft Start
      9. 8.3.9  Output Voltage Setpoint (FB)
      10. 8.3.10 Minimum Controllable On Time
      11. 8.3.11 Error Amplifier and PWM Comparator (FB, EXTCOMP)
      12. 8.3.12 Slope Compensation
      13. 8.3.13 Inductor Current Sense (ISNS+, VOUT)
        1. 8.3.13.1 Shunt Current Sensing
        2. 8.3.13.2 Inductor DCR Current Sensing
      14. 8.3.14 Hiccup Mode Current Limiting
      15. 8.3.15 High-Side and Low-Side Gate Drivers (HO, LO)
      16. 8.3.16 Output Configurations (CNFG)
      17. 8.3.17 Single-Output Dual-Phase Operation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Sleep Mode
      2. 8.4.2 Pulse Frequency Modulation and Synchronization (PFM/SYNC)
      3. 8.4.3 Thermal Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Power Train Components
        1. 9.1.1.1 Buck Inductor
        2. 9.1.1.2 Output Capacitors
        3. 9.1.1.3 Input Capacitors
        4. 9.1.1.4 Power MOSFETs
        5. 9.1.1.5 EMI Filter
        6. 9.1.1.6 Active EMI Filter
      2. 9.1.2 Error Amplifier and Compensation
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 – High-Efficiency 2.1-MHz Synchronous Buck Regulator
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2  Custom Design With Excel Quickstart Tool
          3. 9.2.1.2.3  Buck Inductor
          4. 9.2.1.2.4  Current-Sense Resistance
          5. 9.2.1.2.5  Output Capacitors
          6. 9.2.1.2.6  Input Capacitors
          7. 9.2.1.2.7  Frequency Set Resistor
          8. 9.2.1.2.8  Feedback Resistors
          9. 9.2.1.2.9  Compensation Components
          10. 9.2.1.2.10 Active EMI Components
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Design 2 – High Efficiency 440-kHz Synchronous Buck Regulator
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Design 3 – Dual-Phase 400-kHz 20-A Synchronous Buck Regulator
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
        3. 9.2.3.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 Power Stage Layout
        2. 9.4.1.2 Gate-Drive Layout
        3. 9.4.1.3 PWM Controller Layout
        4. 9.4.1.4 Active EMI Layout
        5. 9.4.1.5 Thermal Design and Layout
        6. 9.4.1.6 Ground Plane Design
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
        1. 10.1.1.1 Custom Design With WEBENCH® Tools
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
        1. 10.2.1.1 PCB Layout Resources
        2. 10.2.1.2 Thermal Design Resources
    3. 10.3 接收文档更新通知
    4. 10.4 支持资源
    5. 10.5 Trademarks
    6. 10.6 静电放电警告
    7. 10.7 术语表
  11. 11Mechanical, Packaging, and Orderable Information

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机械数据 (封装 | 引脚)
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8.3.1 Input Voltage Range (VIN)

The LM25149-Q1 operational input voltage range is from 3.5 V to 42 V. The device is intended for step-down conversions from 12-V, 24-V, and 48-V supply rails. The application circuit in GUID-D337951F-63ED-478D-A264-C06A4CF5CCC4.html#SNVSB29620 shows all the necessary components to implement an LM25149-Q1 based wide-VIN single-output step-down regulator using a single supply. The LM25149-Q1 uses an internal LDO to provide a 5-V VCC bias rail for the gate drive and control circuits (assuming the input voltage is higher than 5 V with additional voltage margin necessary for the subregulator dropout specification).

In high input voltage applications, take extra care to ensure that the VIN and SW pins do not exceed their absolute maximum voltage rating of 47 V during line or load transient events. Voltage excursions that exceed the applicable voltage specifications can damage the device.

Care must be taken in applications where there are fast input transients that cause the voltage at VIN to suddenly drop more than 2 V below the VOUT setpoint. The LM25149-Q1 has an internal ESD diode from the VOUT to the VIN pins that can conduct under such conditions causing the output to discharge. To prevent damage to the internal ESD diode under the said conditions, TI recommends adding a Schottky diode in series with the VIN pin of the LM25149-Q1 to prevent reverse current flow from VOUT to VIN.

As VIN approaches VOUT, the LM25149-Q1 skips tOFF cycles to allow the controller to extend its duty cycle up to approximately 99%. Refer to #GUID-DA313D0A-F01C-444E-A0C5-D18BF22FBD5A.

Use #GUID-9DFE93F7-9395-44D5-B215-6DCC7733D994 to calculate when the LM25149-Q1 enters dropout mode.

Equation 1. V I N = V O U T ×   t P t P   -   t O F F
  • tP is the oscillator period
  • tOFF is the minimum off time, typical 90 ns

Figure 8-1 Dropout Mode Operation