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

7.2.2.6 CO Selection

None of the required CO output capacitance is contained within the module. A minimum value of 200 μF is required based on the values of internal compensation in the error amplifier. Low ESR tantalum, organic semiconductor or specialty polymer capacitor types are recommended for obtaining lowest ripple. The output capacitor CO may consist of several capacitors in parallel placed in close proximity to the module. The output capacitor assembly must also meet the worst case minimum ripple current rating of 0.5 × ILRP-P, as calculated in Equation 14. Beyond that, additional capacitance will reduce output ripple so long as the ESR is low enough to permit it. Loop response verification is also valuable to confirm closed loop behavior.

For applications with dynamic load steps; the following equation provides a good first pass approximation of CO for load transient requirements. Where VO-Tran is 100 mV on a 3.3-V output design.

Equation 8. CO ≥ IO-Tran / (VO-Tran – ESR × IO-Tran) × (Fsw / VO)

Solving:

Equation 9. CO ≥ 4.5 A / (0.1 V – 0.007 × 4.5 A) × ( 800000 Hz / 3.3 V) ≥ 271 μF
Note:

The stability requirement for 200-µF minimum output capacitance will take precedence.

One recommended output capacitor combination is a 220-µF, 7-mΩ ESR specialty polymer cap in parallel with a 100-µF, 6.3-V X5R ceramic. This combination provides excellent performance that may exceed the requirements of certain applications. Additionally some small ceramic capacitors can be used for high-frequency EMI suppression.