SNVS402I February   2006  – May 2021 LM5009

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
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 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 Control Circuit Overview
      2. 7.3.2 High Voltage Startup Regulator
      3. 7.3.3 Regulation Comparator
      4. 7.3.4 Overvoltage Comparator
      5. 7.3.5 On-Time Generator
      6. 7.3.6 Current Limit
      7. 7.3.7 N-Channel Buck Switch and Driver
      8. 7.3.8 Thermal Protection
    4. 7.4 Device Functional 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 Output Resistor Divider Selection
        2. 8.2.2.2 Frequency Selection
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 VCC and Bootstrap Capacitor
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Current Limit Off-Timer Setting
        7. 8.2.2.7 Rectifier Diode Selection
        8. 8.2.2.8 Input Capacitor Selection
        9. 8.2.2.9 Ripple Configuration
      3. 8.2.3 Application Curves
    3. 8.3 Do's and Don'ts
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.7 Rectifier Diode Selection

D1: The important parameters are reverse recovery time and forward voltage. Reverse recovery time determines how long the reverse current surge lasts each time that the buck switch is turned on. The forward voltage drop is significant in the event that the output is short-circuited because only this diode voltage forces the inductor current to reduce during the forced off-time. For this reason, a higher voltage is better, although higher voltages affect efficiency. A good choice is an ultrafast or Schottky diode with a reverse recovery time of approximately 30 ns and a forward voltage drop of approximately 0.7 V. Other types of diodes can have a lower forward voltage drop, but can also have longer recovery times or greater reverse leakage. The D1 reverse voltage rating must be at least as great as the maximum VIN, and the D1 current rating must be greater than the maximum current limit threshold (370 mA).