SNVSCZ9 October   2026 LMR70410

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  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 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 Fixed Frequency Peak Current Mode Control
      2. 7.3.2 Enable and Undervoltage Lockout
      3. 7.3.3 Soft Start and Recovery From Dropout
      4. 7.3.4 Adjustable Output Voltage
      5. 7.3.5 Minimum ON-Time, Minimum OFF-Time and Frequency Foldback
      6. 7.3.6 Bootstrap Voltage
      7. 7.3.7 Overcurrent and Short-Circuit Protection
      8. 7.3.8 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 CCM Mode
      4. 7.4.4 Light-Load Operation (PFM Version)
      5. 7.4.5 Light-Load Operation (FPWM Version)
  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 Output Voltage Setpoint
        2. 8.2.2.2 Switching Frequency
        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 Bootstrap Capacitor
        7. 8.2.2.7 Undervoltage Lockout Setpoint
        8. 8.2.2.8 Replacing Asynchronous Converter
      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 Compact Layout for EMI Reduction
        2. 8.4.1.2 Feedback Resistors
      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
    1. 11.1 Mechanical Data

7.3.3 Soft Start and Recovery From Dropout

The LMR70410 uses soft start to prevent output voltage overshoots and large inrush currents during start-up. The soft-start time is fixed internally at 1.8ms (typical). The LMR70410 device operates correctly even if there is a voltage present on the output before activation.

To start up the LMR70410 and initiate the soft-start sequence, the voltage applied to the VIN and EN pins must exceed VINUVLO(R) and VEN(R) respectively. After these conditions are met, the soft-start sequence initiates and the output voltage reaches the set-point in 1.8ms (typical).

Dropout occurs when the input voltage falls below the voltage level of the output voltage setpoint. After the input voltage increases, the output voltage increases with the same slope as during soft start.