ZHCSSO4D September   2010  – December 2023 TPS74801-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  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: IOUT = 50 mA
    7. 5.7 Typical Characteristics: IOUT = 1 A
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Programmable Soft-Start
      2. 6.3.2 Sequencing Requirements
      3. 6.3.3 Output Noise
      4. 6.3.4 Enable and Shutdown
      5. 6.3.5 Power Good
      6. 6.3.6 Internal Current Limit
      7. 6.3.7 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
  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 Input, Output, and Bias Capacitor Requirements
        2. 7.2.2.2 Transient Response
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Layout Recommendations and Power Dissipation
        2. 7.4.1.2 Estimating Junction Temperature
      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 接收文档更新通知
    3. 8.3 支持资源
    4. 8.4 Trademarks
    5. 8.5 静电放电警告
    6. 8.6 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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6.3.3 Output Noise

The TPS74801-Q1 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 0.001-μF soft-start capacitor, the output noise is reduced by half and is typically 30-μVRMS for a 1.2-V output (10 Hz to 100 kHz). Further increasing CSS has little effect on noise. Because most of the output noise is generated by the internal reference, the noise is a function of the set output voltage. The following equations calculate the RMS noise with a 0.001-μF soft-start capacitor for the legacy and new chip, respectively:

Equation 3. V N = 25 ( μ V R M S V ) × V O U T ( V ) (Legacy Chip)
Equation 4. V N = 20 ( μ V R M S V ) × V O U T ( V ) (New Chip)

The low output noise of the TPS74801-Q1 makes the device a good choice for powering transceivers, PLLs, or other noise-sensitive circuitry.