SNVS639G December   2009  – December 2015 LM21305

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Synchronous DC-DC Switching Converter
      2. 8.3.2  Peak Current-Mode Control
      3. 8.3.3  Switching Frequency Setting and Synchronization
      4. 8.3.4  Light-Load Operation
      5. 8.3.5  Precision Enable
      6. 8.3.6  Device Enable, Soft-Start, and Pre-Bias Startup Capability
      7. 8.3.7  Peak Current Protection and Negative Current Limiting
      8. 8.3.8  PGOOD Indicator
      9. 8.3.9  Internal Bias Regulators
      10. 8.3.10 Minimum On-Time Considerations
    4. 8.4 Device Functional Modes
      1. 8.4.1 Overvoltage and Undervoltage Handling
      2. 8.4.2 Undervoltage Lockout (UVLO)
      3. 8.4.3 Thermal Protection
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Setting the Output Voltage
        2. 9.2.2.2  Calculating the Duty Cycle
        3. 9.2.2.3  Input Capacitors
        4. 9.2.2.4  AVIN Filter
        5. 9.2.2.5  Switching Frequency Selection
        6. 9.2.2.6  Filter Inductor
        7. 9.2.2.7  Output Capacitor
        8. 9.2.2.8  Efficiency Considerations
        9. 9.2.2.9  Load Current Derating When Duty Cycle Exceeds 50%
        10. 9.2.2.10 Control Loop Compensation
        11. 9.2.2.11 Compensation Components Selection
        12. 9.2.2.12 Plotting the Loop Gain
        13. 9.2.2.13 High Frequency Considerations
        14. 9.2.2.14 Bootstrap Capacitor
        15. 9.2.2.15 5V0 and 2V5 Capacitors
        16. 9.2.2.16 Maximum Ambient Temperature
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Compact PCB Layout for EMI Reduction
      2. 11.1.2 Ground Plane and Thermal Design Considerations
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
      2. 12.2.2 PCB Layout Resources
      3. 12.2.3 Resources for Thermal PCB Design
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

12 Device and Documentation Support

12.1 Device Support

12.1.1 Development Support

12.2 Documentation Support

12.2.1 Related Documentation

  • AN-2042 LM21305 Evaluation Board, SNVA432
  • AN-2175 LM21305 POL Demonstration Module and Reference Design, SNVA497
  • AN-2162 Simple Success with Conducted EMI from DC-DC Converters, SNVA489
  • AN-1187 Leadless Leadframe Package (LLP), SNOA401
  • Using New Thermal Metrics Application Report, SBVA025
  • 6/4-Bit VID Programmable Current DAC for Point of Load Regulators with Adjustable Start-Up Current, SNVS822
  • Semiconductor and IC Package Thermal Metrics, SPRA953

12.2.2 PCB Layout Resources

  • AN-1149 Layout Guidelines for Switching Power Supplies, SNVA021
  • AN-1229 Simple Switcher PCB Layout Guidelines, SNVA054
  • Constructing Your Power Supply – Layout Considerations, SLUP230
  • Low Radiated EMI Layout Made SIMPLE with LM4360x and LM4600x, SNVA721

12.2.3 Resources for Thermal PCB Design

  • AN-2020 Thermal Design By Insight, Not Hindsight, SNVA419
  • AN-1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Pad Packages, SNVA183
  • SPRA953B Semiconductor and IC Package Thermal Metrics, SPRA953
  • SNVA719 Thermal Design made Simple with LM43603 and LM43602, SNVA719
  • SLMA002 PowerPAD™ Thermally Enhanced Package, SLMA002
  • SLMA004 PowerPAD Made Easy, SLMA004
  • SBVA025 Using New Thermal Metrics, SBVA025

12.3 Community Resources

The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use.

    TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers.
    Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support.

12.4 Trademarks

E2E is a trademark of Texas Instruments.

PowerPAD is a trademark of TI.

WEBENCH is a registered trademark of TI.

All other trademarks are the property of their respective owners.

12.5 Electrostatic Discharge Caution

esds-image

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.

12.6 Glossary

SLYZ022 — TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.