SNVS600J December   2008  – June 2022 LM5088 , LM5088-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings: LM5088
    3. 6.3 ESD Ratings: LM5088-Q1
    4. 6.4 Recommended Operating Conditions
    5. 6.5 Thermal Information
    6. 6.6 Electrical 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 Low-Dropout Regulator
      2. 7.3.2  Line Undervoltage Detector
      3. 7.3.3  Oscillator and Sync Capability
      4. 7.3.4  Error Amplifier and PWM Comparator
      5. 7.3.5  Ramp Generator
      6. 7.3.6  Dropout Voltage Reduction
      7. 7.3.7  Frequency Dithering (LM5088-1 Only)
      8. 7.3.8  Cycle-by-Cycle Current Limit
      9. 7.3.9  Overload Protection Timer (LM5088-2 Only)
      10. 7.3.10 Soft Start
      11. 7.3.11 HG Output
      12. 7.3.12 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 EN Pin Modes
  8. 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  Timing Resistor
        2. 8.2.2.2  Output Inductor
        3. 8.2.2.3  Current Sense Resistor
        4. 8.2.2.4  Ramp Capacitor
        5. 8.2.2.5  Output Capacitors
        6. 8.2.2.6  Input Capacitors
        7. 8.2.2.7  VCC Capacitor
        8. 8.2.2.8  Bootstrap Capacitor
        9. 8.2.2.9  Soft-Start Capacitor
        10. 8.2.2.10 Output Voltage Divider
        11. 8.2.2.11 UVLO Divider
        12. 8.2.2.12 Restart Capacitor (LM5008-2 Only)
        13. 8.2.2.13 MOSFET Selection
        14. 8.2.2.14 Diode Selection
        15. 8.2.2.15 Snubber Components Selection
        16. 8.2.2.16 Error Amplifier Compensation
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Thermal Considerations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.15 Snubber Components Selection

Excessive ringing and spikes can cause erratic operation and couple spikes and noise to the output. Voltage spikes beyond the rating of the LM5088 or the re-circulating diode can damage these devices. A snubber network across the power diode reduces ringing and spikes at the switching node. Selecting the values for the snubber is best accomplished through empirical methods. First, make sure that the lead lengths for the snubber connections are very short. For the current levels typical for the LM5088, a resistor value between 3 Ω and 10 Ω must be adequate. As a rule of thumb, a snubber capacitor, which is four to five times the junction temperature of the Schottky diode reduce spikes adequately. Increasing the value of the snubber capacitor results in more damping but also results in higher losses. The power dissipation of the resistor is independent of the resistance value as the resistor dissipates the energy stored by the snubber capacitor. The power dissipation of the resistor can be approximated as:

Equation 27. PR_SNUB = CSNUB × VIN(max)2 × fSW