SNVSBV6B December   2020  – January 2023 LM25149-Q1

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
    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 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.3.1 Design Requirements

Table 9-7 shows the intended input, output, and performance parameters for this automotive design example.

Table 9-7 Design Parameters
DESIGN PARAMETER VALUE
Input voltage range (steady-state) 8 V to 36 V
Min transient input voltage (cold crank) 4 V
Max transient input voltage (load dump) 40 V
Output voltage 3.3 V
Output current 20 A
Switching frequency 400 kHz
Output voltage regulation ±1%
Standby current, no-load 44 µA
Shutdown current 4.6 µA
Soft-start time 3 ms

The switching frequency is set at 400 kHz by resistors RRT1 and RRT2. The selected buck regulator powertrain components are cited in Table 9-6, 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 Power MOSFETs.

Table 9-8 List of Materials for Application Circuit 4
REFERENCE DESIGNATOR QTY SPECIFICATION MANUFACTURER PART NUMBER
CIN 4 10 µF, 50 V, X7S, 1210, ceramic, AEC-Q200 TDK CGA6P3X7S1H106K250AB
Murata GCM32EC71H106KA03
CO 8 47 µF, 6.3 V, X7R, 1210, ceramic, AEC-Q200 Murata GCM32ER70J476KE19L
47 µF, 10 V, X7S, 1210, ceramic, AEC-Q200 TDK CGA6P1X7S1A476M250AC
4 100 µF, 6.3 V, X7S, 1210, ceramic, AEC-Q200 Murata GRT32EC70J107ME13
LO1, LO2 2 2.2 μH, 4.3 mΩ, 12.5 A, 6.7 × 6.5 × 6.1 mm, AEC-Q200 Coilcraft XGL6060-222MEC
2.2 µH, 6.5 mΩ, 10 A, 10 × 11 × 3.8 mm, AEC-Q200 Würth Electronik 74437368022
Q1, Q2, Q3, Q4 4 40 V, 4.7 mΩ, 7 nC, SON 5 × 6, AEC-Q101 Infineon IAUC60N04S6L039
RS1, RS2 2 Shunt, 4 mΩ, 0508, 1 W, AEC-Q200 Susumu

KRL2012E-M-R004-F-T5
U1, U2 2 LM25149-Q1 42-V synchronous buck controller with AEF, AEC-Q100 Texas Instruments LM25149QRGYRQ1
LM25148-Q1 42-V synchronous buck controller, AEC-Q100 Texas Instruments LM25148QRGYRQ1