SNVSCR9A October   2024  – December 2024 LM61480T-Q1 , LM61495T-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
  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 Requirements
    7. 6.7 Switching 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  Output Voltage Selection
      2. 7.3.2  Enable EN Pin and Use as VIN UVLO
      3. 7.3.3  SYNC/MODE Uses for Synchronization
      4. 7.3.4  Clock Locking
      5. 7.3.5  Adjustable Switching Frequency
      6. 7.3.6  RESET Output Operation
      7. 7.3.7  Internal LDO, VCC UVLO, and BIAS Input
      8. 7.3.8  Bootstrap Voltage and VCBOOT-UVLO (CBOOT Pin)
      9. 7.3.9  Adjustable SW Node Slew Rate
      10. 7.3.10 Spread Spectrum
      11. 7.3.11 Soft Start and Recovery From Dropout
      12. 7.3.12 Overcurrent and Short-Circuit Protection
      13. 7.3.13 Hiccup
      14. 7.3.14 Thermal Shutdown
    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 Peak Current Mode Operation
        2. 7.4.3.2 Auto Mode Operation
          1. 7.4.3.2.1 Diode Emulation
        3. 7.4.3.3 FPWM Mode Operation
        4. 7.4.3.4 Minimum On-time (High Input Voltage) Operation
        5. 7.4.3.5 Dropout
        6. 7.4.3.6 Recovery from Dropout
        7. 7.4.3.7 Other Fault Modes
  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  CFF and RFF Selection
        10. 8.2.2.10 RSPSP Selection
        11. 8.2.2.11 RT Selection
        12. 8.2.2.12 RMODE Selection
        13. 8.2.2.13 External UVLO
        14. 8.2.2.14 Maximum Ambient Temperature
      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 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
    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 Glossary
    7. 9.7 Electrostatic Discharge Caution
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.5 Adjustable Switching Frequency

The RT pin is configurable. This pin can be tied to VCC for 400kHz operation, grounded for 2.2MHz operation, or a resistor to AGND can be used to set an adjustable operating frequency. See Figure 7-6 for resistor values. Note that if a resistor value falls outside of the recommended range, the fall can cause the LM614xxT-Q1 to revert to 400kHz or 2.2MHz. Do not apply a pulsed signal to this pin to force synchronization. If synchronization is needed, see the SYNC/MODE pin in Section 7.3.3.

Equation 3. R T k Ω = 16.4 f s w ( M H z ) - 0.633

For example, for fSW = 2.2MHz, RT = (16.4 / 2.2) – 0.633 = 6.82kΩ, so a 6.81kΩ resistor is selected as the closest choice.

LM61480T-Q1 LM61495T-Q1 Setting Clock Frequency Figure 7-6 Setting Clock Frequency