SNVS625G February   2011  – March 2022 LM21215

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 Ratings
    4. 6.4 Electrical Characteristics
    5. 6.5 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 Precision Enable
      2. 7.3.2 UVLO
      3. 7.3.3 Current Limit
      4. 7.3.4 Short-Circuit Protection
      5. 7.3.5 Thermal Protection
      6. 7.3.6 Light Load Operation
      7. 7.3.7 Power Good Flag
    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 Typical Application 1
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2 Output Voltage
          3. 8.2.1.2.3 Precision Enable
          4. 8.2.1.2.4 Soft Start
          5. 8.2.1.2.5 Inductor Selection
          6. 8.2.1.2.6 Output Capacitor Selection
          7. 8.2.1.2.7 Input Capacitor Selection
          8. 8.2.1.2.8 Programmable Current Limit
          9. 8.2.1.2.9 Control Loop Compensation
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Typical Application Schematic 2
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
  9. 9 Layout
    1. 9.1 Layout Considerations
    2. 9.2 Layout Example
      1. 9.2.1 Thermal Considerations
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
      2. 10.1.2 Development Support
        1. 10.1.2.1 Custom Design With WEBENCH® Tools
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.4 Short-Circuit Protection

In the unfortunate event that the output is shorted with a low impedance to ground, the LM21215 limits the current into the short by resetting the device. A short-circuit condition is sensed by a current-limit condition coinciding with a voltage on the FB pin that is lower than 100 mV. When this condition occurs, the device begins its reset sequence, turning off both power FETs and discharging the soft-start capacitor after tRESETSS (nominally 110 µs). The device will then attempt to restart. If the short-circuit condition still exists, it will reset again, and repeat until the short-circuit is cleared. The reset prevents excess current flowing through the FETs in a highly inefficient manner, potentially causing thermal damage to the device or the bus supply.

GUID-561B65D2-9328-4EBA-993B-D8DA5C7D84D5-low.gifFigure 7-1 Current Limit Conditions