SNVSBR8F March   2020  – August 2026 LMQ61460

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 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  EN/SYNC Uses for Enable and VIN UVLO
      2. 7.3.2  EN/SYNC Pin Uses for Synchronization
      3. 7.3.3  Adjustable Switching Frequency
      4. 7.3.4  Clock Locking
      5. 7.3.5  PGOOD Output Operation
      6. 7.3.6  Internal LDO, VCC UVLO, and BIAS Input
      7. 7.3.7  Bootstrap Voltage and VCBOOT-UVLO (CBOOT Pin)
      8. 7.3.8  Adjustable SW Node Slew Rate
      9. 7.3.9  Spread Spectrum
      10. 7.3.10 Soft Start and Recovery From Dropout
      11. 7.3.11 Output Voltage Setting
      12. 7.3.12 Overcurrent and Short-Circuit Protection
      13. 7.3.13 Thermal Shutdown
      14. 7.3.14 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 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Choosing the Switching Frequency
        2. 8.2.2.2  Setting the Output Voltage
        3. 8.2.2.3  Inductor Selection
        4. 8.2.2.4  Output Capacitor Selection
        5. 8.2.2.5  Input Capacitor Selection
        6. 8.2.2.6  BOOT Capacitor
        7. 8.2.2.7  BOOT Resistor
        8. 8.2.2.8  VCC
        9. 8.2.2.9  BIAS
        10. 8.2.2.10 CFF and RFF Selection
        11. 8.2.2.11 External UVLO
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Ground and Thermal Considerations
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.11 Output Voltage Setting

A feedback resistor divider network between the output voltage and the FB pin is used to set output voltage level. See Figure 7-11.

LMQ61460 Setting Output Voltage of Adjustable VersionsFigure 7-11 Setting Output Voltage of Adjustable Versions

The device uses a 1V reference voltage for the feedback (FB) pin. The FB pin voltage is regulated by the internal controller to be the same as the reference voltage. The output voltage level is then set by the ratio of the resistor divider. use Equation 3 to determine RFBB for a desired output voltage and a given RFBT. Usually RFBT is between 10kΩ and 1MΩ. 100kΩ is recommended for RFBT for improved noise immunity compared to 1MΩ and reduced current consumption compared to lower resistance values.

Equation 3. LMQ61460

In addition, a feedforward capacitor, CFF, connected in parallel with RFBT can be required to optimize the transient response.