SNVSAA6B February   2015  – December 2024 LMR14050

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Fixed Frequency Peak Current Mode Control
      2. 6.3.2  Slope Compensation
      3. 6.3.3  Sleep Mode
      4. 6.3.4  Low Dropout Operation and Bootstrap Voltage (BOOT)
      5. 6.3.5  Adjustable Output Voltage
      6. 6.3.6  Enable and Adjustable Undervoltage Lockout
      7. 6.3.7  External Soft Start
      8. 6.3.8  Switching Frequency and Synchronization (RT/SYNC)
      9. 6.3.9  Overcurrent and Short-Circuit Protection
      10. 6.3.10 Overvoltage Protection
      11. 6.3.11 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown Mode
      2. 6.4.2 Active Mode
      3. 6.4.3 CCM Mode
      4. 6.4.4 Light Load Operation
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Output Voltage Set-Point
        2. 7.2.2.2 Switching Frequency
        3. 7.2.2.3 Output Inductor Selection
        4. 7.2.2.4 Output Capacitor Selection
        5. 7.2.2.5 Schottky Diode Selection
        6. 7.2.2.6 Input Capacitor Selection
        7. 7.2.2.7 Bootstrap Capacitor Selection
        8. 7.2.2.8 Soft-start Capacitor Selection
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.9 Overcurrent and Short-Circuit Protection

The LMR14050 is protected from over current condition by cycle-by-cycle current limiting on the peak current of the high-side MOSFET. High-side MOSFET over-current protection is implemented by the nature of the Peak Current Mode control. The high-side switch current is compared to the output of the Error Amplifier (EA) minus slope compensation every switching cycle. Please refer to the Functional Block Diagram for more details. The peak current of high-side switch is limited by a clamped maximum peak current threshold which is constant. So the peak current limit of the high-side switch is not affected by the slope compensation and remains constant over the full duty cycle range.

The LMR14050 also implements a frequency fold-back to protect the converter in severe overcurrent or short conditions. The oscillator frequency is divided by 2, 4, and 8 as the FB pin voltage decrease to 75%, 50%, 25% of VREF. The frequency fold-back increases the off time by increasing the period of the switching cycle, so that it provides more time for the inductor current to ramp down and leads to a lower average inductor current. Lower frequency also means lower switching loss. Frequency fold-back reduces power dissipation and prevents overheating and potential damage to the device.