SNVS680I August   2010  – April 2018 LM25119

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  High Voltage Start-Up Regulator
      2. 7.3.2  UVLO
      3. 7.3.3  Enable 2
      4. 7.3.4  Oscillator and Sync Capability
      5. 7.3.5  Error Amplifiers and PWM Comparators
      6. 7.3.6  Ramp Generator
      7. 7.3.7  Current Limit
      8. 7.3.8  Hiccup Mode Current Limiting
      9. 7.3.9  Soft Start
      10. 7.3.10 HO and LO Output Drivers
      11. 7.3.11 Maximum Duty Cycle
      12. 7.3.12 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Diode Emulation
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Miscellaneous Functions
      2. 8.1.2 Interleaved Two-Phase Operation
      3. 8.1.3 Interleaved 4-Phase Operation
    2. 8.2 Typical Applications
      1. 8.2.1 Dual-output Design Example
        1. 8.2.1.1 Design Requirements
          1. 8.2.1.1.1 External Components
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Timing Resistor
          2. 8.2.1.2.2  Output Inductor
          3. 8.2.1.2.3  Current Sense Resistor
          4. 8.2.1.2.4  Ramp Resistor and Ramp Capacitor
          5. 8.2.1.2.5  Output Capacitors
          6. 8.2.1.2.6  Input Capacitors
          7. 8.2.1.2.7  VCC Capacitor
          8. 8.2.1.2.8  Bootstrap Capacitor
          9. 8.2.1.2.9  Soft Start Capacitor
          10. 8.2.1.2.10 Restart Capacitor
          11. 8.2.1.2.11 Output Voltage Divider
          12. 8.2.1.2.12 UVLO Divider
          13. 8.2.1.2.13 MOSFET Selection
          14. 8.2.1.2.14 MOSFET Snubber
          15. 8.2.1.2.15 Error Amplifier Compensation
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Two-Phase Design Example
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Switching Jitter Root Causes and Solutions
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.1.2.14 MOSFET Snubber

A resistor-capacitor snubber network across the low-side MOSFET reduces ringing and spikes at the switching node. Excessive ringing and spikes can cause erratic operation and couple noise to the output. Selecting the values for the snubber is best accomplished through empirical methods. First, make sure the lead lengths for the snubber connections are very short. Start with a resistor value between 5 and 50 Ω. Increasing the value of the snubber capacitor results in more damping, but higher snubber losses. Select a minimum value for the snubber capacitor that provides adequate damping of the spikes on the switch waveform at high load. A snubber may not be necessary with an optimized layout.