SNVS036L April   2000  – June 2025 LM2670

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 – 3.3 V
    6. 5.6  Electrical Characteristics – 5 V
    7. 5.7  Electrical Characteristics – 12 V
    8. 5.8  Electrical Characteristics – ADJ
    9. 5.9  Electrical Characteristics – All Output Voltage Versions
    10. 5.10 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 Switch Output
      2. 6.3.2 Input
      3. 6.3.3 C Boost
      4. 6.3.4 Ground
      5. 6.3.5 SYNC
      6. 6.3.6 Feedback
      7. 6.3.7 ON/OFF
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown Mode
      2. 6.4.2 Active Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Design Considerations
      2. 7.1.2 Inductor
      3. 7.1.3 Output Capacitor
      4. 7.1.4 Input Capacitor
      5. 7.1.5 Catch Diode
      6. 7.1.6 Boost Capacitor
      7. 7.1.7 Sync Components
      8. 7.1.8 Additional Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Typical Application for All Output Voltage Versions
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Capacitor Selection Guides
          2. 7.2.1.2.2 Inductor Selection Guides
          3. 7.2.1.2.3 Custom Design with WEBENCH® Tools
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Fixed Output Voltage Application
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
          1. 7.2.2.2.1 Capacitor Selection Guides
      3. 7.2.3 Adjustable Output Voltage Application
        1. 7.2.3.1 Design Requirements
        2. 7.2.3.2 Detailed Design Procedure
          1. 7.2.3.2.1 Capacitor Selection Guides
    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 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
      2. 8.1.2 Development Support
        1. 8.1.2.1 Custom Design with WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information
    1. 10.1 DAP (VSON Package)

Package Options

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

7.1.5 Catch Diode

When the power switch in the LM2670 turns OFF, the current through the inductor continues to flow. The path for this current is through the diode connected between the switch output and ground. This forward biased diode clamps the switch output to a voltage less than ground. This negative voltage must be greater than –1 V so a low voltage drop (particularly at high current levels) Schottky diode is recommended. Total efficiency of the entire power supply is significantly impacted by the power lost in the output catch diode. The average current through the catch diode is dependent on the switch duty cycle (D) and is equal to the load current times (1-D). Use of a diode rated for much higher current than is required by the actual application helps to minimize the voltage drop and power loss in the diode.

During the switch ON time the diode is reversed biased by the input voltage. The reverse voltage rating of the diode must be at least 1.3 times greater than the maximum input voltage.