SNVS686K March   2011  – May 2024 LMZ22005

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
    6. 5.6 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 Synchronization Input
      2. 6.3.2 Output Overvoltage Protection
      3. 6.3.3 Current Limit
      4. 6.3.4 Thermal Protection
      5. 6.3.5 Prebiased Start-Up
    4. 6.4 Device Functional Modes
      1. 6.4.1 Discontinuous And Continuous Conduction Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Design Steps
        2. 7.2.2.2 Enable Divider, RENT, RENB and RENH Selection
        3. 7.2.2.3 Output Voltage Selection
        4. 7.2.2.4 Soft-start Capacitor Selection
        5. 7.2.2.5 Tracking Supply Divider Option
        6. 7.2.2.6 CO Selection
        7. 7.2.2.7 CIN Selection
        8. 7.2.2.8 Discontinuous And Continuous Conduction Modes Selection
      3. 7.2.3 Application Curves
  9. 8 Power Supply Recommendations
  10. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Examples
    3. 9.3 Power Dissipation and Thermal Considerations
    4. 9.4 Power Module SMT Guidelines
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.2.2.5 Tracking Supply Divider Option

The tracking function allows the module to be connected as a slave supply to a primary voltage rail (often the 3.3-V system rail) where the slave module output voltage is lower than that of the master. Proper configuration allows the slave rail to power up coincident with the master rail such that the voltage difference between the rails during ramp-up is small (that is, <0.15 V typical). The values for the tracking resistive divider must be selected such that the effect of the internal 50-µA current source is minimized. In most cases the ratio of the tracking divider resistors is the same as the ratio of the output voltage setting divider. Proper operation in tracking mode dictates the soft-start time of the slave rail be shorter than the master rail; a condition that is easy satisfy because the CSS cap is replaced by RTKB. The tracking function is only supported for the power up interval of the master supply; once the SS/TRK rises past 0.8V the input is no longer enabled and the 50-µA internal current source is switched off.

LMZ22005 Tracking Option Input DetailFigure 7-3 Tracking Option Input Detail