SNVSC78D February   2022  – September 2026 LMQ66410 , LMQ66420 , LMQ66430

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  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 System Characteristics
    7. 6.7 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  Enable, Start-Up, and Shutdown
      2. 7.3.2  Adjustable Switching Frequency (With RT)
      3. 7.3.3  Power-Good Output Operation
      4. 7.3.4  Internal LDO, VCC, and VOUT/FB Input
      5. 7.3.5  Bootstrap Voltage and VBOOT-UVLO (BOOT Terminal)
      6. 7.3.6  Output Voltage Selection
      7. 7.3.7  Spread Spectrum
      8. 7.3.8  Soft Start and Recovery from Dropout
        1. 7.3.8.1 Recovery From Dropout
      9. 7.3.9  Current Limit and Short Circuit
      10. 7.3.10 Thermal Shutdown
      11. 7.3.11 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 Reduction
        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 Application
      1. 8.2.1 Synchronous Buck Regulator at 400kHz
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1  Choosing the Switching Frequency
        2. 8.2.3.2  Setting the Output Voltage
          1. 8.2.3.2.1 VOUT / FB for Adjustable Output
        3. 8.2.3.3  Inductor Selection
        4. 8.2.3.4  Output Capacitor Selection
        5. 8.2.3.5  Input Capacitor Selection
        6. 8.2.3.6  CBOOT
        7. 8.2.3.7  VCC
        8. 8.2.3.8  CFF Selection
        9. 8.2.3.9  External UVLO
        10. 8.2.3.10 Maximum Ambient Temperature
      4. 8.2.4 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Ground and Thermal Considerations
      2. 8.5.2 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 Device Nomenclature
    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

8.2.3.7 VCC

The VCC pin is the output of the internal LDO used to supply the control circuits of the regulator. This output requires a 1µF, 16V ceramic capacitor connected from VCC to GND for proper operation. In general, this output must not be loaded with any external circuitry. However, this output can be used to supply the pullup for the power-good function (see Section 7.3.3). A value in the range of 10kΩ to 100kΩ is a good choice in this case. The nominal output voltage on VCC is 3.3V; see the Electrical Characteristics for limits.