SLVSIY7 August   2025 LM5168E

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 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  Control Architecture
      2. 7.3.2  Internal VCC Regulator and Bootstrap Capacitor
      3. 7.3.3  Internal Soft Start
      4. 7.3.4  On-Time Generator
      5. 7.3.5  Current Limit
      6. 7.3.6  N-Channel Buck Switch and Driver
      7. 7.3.7  Synchronous Rectifier
      8. 7.3.8  Enable/Undervoltage Lockout (EN/UVLO)
      9. 7.3.9  Power Good (PGOOD)
      10. 7.3.10 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 Sleep Mode
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Buck Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Switching Frequency (RT)
        2. 8.2.2.2 Buck Inductor Selection
        3. 8.2.2.3 Setting the Output Voltage
        4. 8.2.2.4 Type 3 Ripple Network
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Input Capacitor Considerations
        7. 8.2.2.7 CBST Selection
        8. 8.2.2.8 Example Design Summary
      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 PCB Layout for EMI Reduction
        2. 8.4.1.2 Feedback Resistors
      2. 8.4.2 Thermal Considerations
      3. 8.4.3 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 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.4 On-Time Generator

The on time of the LM5168E high-side FET is determined by the RT resistor and is inversely proportional to the input voltage, VIN. The inverse relationship with VIN results in a nearly constant frequency as VIN is varied. Use Section 7.3.4 to calculate the on time, where RT is in kΩ.

Equation 9. TON= RT2.5×VIN

Use Equation 10 to determine the RT resistor to set a specific switching frequency in CCM, where FSW is in kHz.

Equation 10. R T = 2500 × V O U T F S W     k Ω

Select RT for a minimum on time (at maximum VIN) greater than 50ns for proper buck operation. In addition to this minimum on time, the maximum frequency for this device is limited to 1MHz.