SNVSBV5B December   2020  – December 2021 LM25149

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  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
  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 Active EMI Layout
      5. 11.1.5 Thermal Design and Layout
      6. 11.1.6 Ground Plane Design
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
      2. 12.1.2 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 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.2.1.1 Design Requirements

Table 9-3 shows the intended input, output, and performance parameters for this design example. Reference the LM25149-Q1EVM-2100 evaluation module.

Table 9-3 Design Parameters
DESIGN PARAMETERVALUE
Input voltage range (steady-state)8 V to 18 V
Min transient input voltage 5.5 V
Max transient input voltage 36 V
Output voltage5 V
Output current8 A
Switching frequency2.1 MHz
Output voltage regulation±1%
Standby current, no-load12 µA
Shutdown current2.3 µA
Soft-start time3 ms

The switching frequency is set at 2.1 MHz by resistor RRT. In terms of control loop performance, the target loop crossover frequency is 60 kHz with a phase margin greater than 50°.

The selected buck regulator powertrain components are cited in Table 9-4, and many of the components are available from multiple vendors. The MOSFETs in particular are chosen for both lowest conduction and switching power loss, as discussed in detail in Section 9.1.1.4. This design uses a low-DCR metal-powder composite inductor and ceramic output capacitor implementation.

Table 9-4 List of Materials for Application Circuit 1
REFERENCE DESIGNATORQTYSPECIFICATIONMANUFACTURERPART NUMBER
CIN210 µF, 50 V, X7S, 1210, ceramicTaiyo YudenUMJ325KB7106KMHT
MurataGCM32EC71H106KA03
TDKCGA6P3X7S1H106K250AB
CO447 µF, 6.3 V, X7R, 1210, ceramicMurataGCM32ER70J476KE19L
Taiyo YudenJMK325B7476KMHTR
47 µF, 10 V, X7S, 1210, ceramicTDKCGA6P1X7S1A476M250AC
LO 1 0.68 μH, 2.9 mΩ, 15.3 A, 6.7 × 6.5 × 3.1 mm Coilcraft XGL6030-681MEB
0.56 μH, 3.6 mΩ, 13 A, 6.6 × 6.6 × 4.8 mmWürth Electronik744373490056
0.68 µH, 4.5 mΩ, 22 A, 6.95 × 6.6 × 2.8 mmCyntecVCMV063T-R68MN2T
Q1 1 40 V, 4.7 mΩ, 12 nC, SON 5 × 6 Texas Instruments CSD18503Q5A
Q2 1 40 V, 2.7 mΩ, 35 nC, SON 5 × 6 Texas Instruments CSD18511Q5A
RS1Shunt, 5 mΩ, 0508, 1 WSusumu

KRL2012E-M-R005-F-T5

U11 LM25149 42-V synchronous buck controller with AEFTexas Instruments LM25149RGYR