SLVSDV6C November   2017  – November 2019 TPS62821 , TPS62822 , TPS62823

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Schematic space space space space
      2.      Efficiency vs Output Current space
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin 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 Enable / Shutdown and Output Discharge
      2. 8.3.2 Soft-Start
      3. 8.3.3 Power Good (PG)
      4. 8.3.4 Undervoltage Lockout (UVLO)
      5. 8.3.5 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Pulse Width Modulation (PWM) Operation
      2. 8.4.2 Power Save Mode (PSM) Operation
      3. 8.4.3 Minimum Duty Cycle and 100% Mode Operation
      4. 8.4.4 Current Limit and Short Circuit 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 Custom Design With WEBENCH® Tools
        2. 9.2.2.2 Setting the Adjustable Output Voltage
        3. 9.2.2.3 Feed-forward Capacitor Selection
        4. 9.2.2.4 Output Filter Selection
        5. 9.2.2.5 Inductor Selection
        6. 9.2.2.6 Output Capacitor Selection
        7. 9.2.2.7 Input Capacitor Selection
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Related Links
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.2.3 Feed-forward Capacitor Selection

A feedforward capacitor (CFF) is recommended in parallel with R1. Equation 5 calculates the CFF value. For the recommended 100k value for R2, a 120 pF feed forward capacitor is used.

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Equation 5. TPS62821 TPS62822 TPS62823 SLVSDV6_eqcff.gif

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Figure 47 and Figure 48 show the results of a frequency domain analysis for both use cases, with and without a feed-forward capacitor. The larger unity gain frequency, caused by the feed forward capacitor, results in a significant improvement of the transient response.

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