SBVS066S December   2005  – November 2024 TPS74401

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 Enable, Shutdown
      2. 6.3.2 Power-Good (VQFN Package Only)
      3. 6.3.3 Internal Current Limit
      4. 6.3.4 Thermal Protection
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
      3. 6.4.3 Disabled
    5. 6.5 Programming
      1. 6.5.1 Programmable Soft-Start
      2. 6.5.2 Sequencing Requirements
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Input, Output, and Bias Capacitor Requirements
      2. 7.1.2 Transient Response
      3. 7.1.3 Dropout Voltage
      4. 7.1.4 Output Noise
    2. 7.2 Typical Applications
      1. 7.2.1 Setting the TPS74401
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Using an Auxiliary Bias Rail
      3. 7.2.3 Without an Auxiliary Bias
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Power Dissipation
        2. 7.4.1.2 Thermal Considerations
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
      2. 8.1.2 Device Nomenclature
    2. 8.2 Device Support
      1. 8.2.1 Development Support
        1. 8.2.1.1 Evaluation Modules
        2. 8.2.1.2 Spice Models
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.1.4 Output Noise

The TPS74401 provides low output noise when a soft-start capacitor is used. When the device reaches the end of the soft-start cycle, the soft-start capacitor serves as a filter for the internal reference. By using a 0.001μF soft-start capacitor, the output noise is reduced by half and is typically 19μVRMS for a 1.2V output (100Hz to 100kHz). Noise is a function of the set output voltage because most of the output noise is generated by the internal reference.

The RMS noise with a 0.001μF soft-start capacitor is given in Equation 4 for the legacy chip and Equation 5 for the new chip.

Equation 4. V N μ V R M S = 16 μ V R M S V × V O U T V
Equation 5. V N μ V R M S = 20 μ V R M S V × V O U T V

The low output noise of the TPS74401 makes the device a good choice for powering transceivers, PLLs, or other noise-sensitive circuitry.