SNVSBW0B October   2022  – August 2024 LM64440-Q1 , LM64460-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
    1. 5.1 Wettable Flanks
    2. 5.2 Pinout Design for Clearance and FMEA
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Characteristics
    7. 6.7 Systems Characteristics
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Input Voltage Range (VIN1, VIN2)
      2. 7.3.2  Output Voltage Setpoint (FB)
      3. 7.3.3  Precision Enable and Input Voltage UVLO (EN)
      4. 7.3.4  MODE/SYNC Operation
        1. 7.3.4.1 Level-Dependent MODE/SYNC Control
        2. 7.3.4.2 Pulse-Dependent MODE/SYNC Control
      5. 7.3.5  Clock Locking
      6. 7.3.6  Power-Good Monitor (PGOOD)
      7. 7.3.7  Bias Supply Regulator (VCC, BIAS)
      8. 7.3.8  Bootstrap Voltage and UVLO (CBOOT)
      9. 7.3.9  Spread Spectrum
      10. 7.3.10 Soft Start and Recovery From Dropout
      11. 7.3.11 Overcurrent and Short-Circuit Protection
      12. 7.3.12 Thermal Shutdown
      13. 7.3.13 Input Supply Current
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
        1. 7.4.3.1 CCM Mode
        2. 7.4.3.2 AUTO Mode – Light-Load Operation
          1. 7.4.3.2.1 Diode Emulation
          2. 7.4.3.2.2 Frequency Foldback
        3. 7.4.3.3 FPWM Mode – Light-Load Operation
        4. 7.4.3.4 Minimum On-Time (High Input Voltage) Operation
        5. 7.4.3.5 Dropout
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1 – Automotive Synchronous 6A Buck Regulator at 2.1MHz
        1. 8.2.1.1 Design Requirements
      2. 8.2.2 Design 2 – Automotive Synchronous 4A Buck Regulator at 2.1MHz
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1  Custom Design With WEBENCH® Tools
          2. 8.2.2.2.2  Setting the Output Voltage
          3. 8.2.2.2.3  Choosing the Switching Frequency
          4. 8.2.2.2.4  Inductor Selection
          5. 8.2.2.2.5  Output Capacitor Selection
          6. 8.2.2.2.6  Input Capacitor Selection
          7. 8.2.2.2.7  Bootstrap Capacitor
          8. 8.2.2.2.8  VCC Capacitor
          9. 8.2.2.2.9  BIAS Power Connection
          10. 8.2.2.2.10 Feedforward Network
          11. 8.2.2.2.11 Input Voltage UVLO
        3. 8.2.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Thermal Design and Layout
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Development Support
        1. 9.1.2.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Tape and Reel Information

Package Options

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

7.3.4 MODE/SYNC Operation

The LM644x0-Q1 features selectable operating modes through the MODE/SYNC input pin. The LM644x0-Q1 can operate in one of three selectable modes:

  • AUTO Mode: Pulse frequency modulation (PFM) operation is enabled during light load and diode emulation to prevent reverse current through the inductor. See Section 7.4.3.2 for more detail.
  • FPWM Mode: In FPWM mode, diode emulation is disabled, allowing current to flow backwards through the inductor. This allows operation at full frequency even without load current. See Section 7.4.3.3 for more detail.
  • SYNC Mode: The LM644x0-Q1 clock locks to an external signal applied to the MODE/SYNC pin. As long as the output voltage can be regulated at full frequency and is not limited by the minimum off time or minimum on time, the clock frequency is matched to the frequency of the signal applied to the MODE/SYNC pin. While the LM644x0-Q1 is in SYNC mode, it operates as though in FPWM mode: diode emulation is disabled, allowing the frequency applied to the MODE/SYNC pin to be matched without an applied load at the output.

In addition, the MODE/SYNC pin can be used to activate or deactivate the spread spectrum feature of the LM644x0-Q1. The MODE/SYNC pin can be configured in two ways: level-dependent MODE/SYNC control (see Section 7.3.4.1) or pulse-dependent MODE/SYNC control (see Section 7.3.4.2).