ZHCSN49N January   2007  – June 2024

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 Diagrams
    3. 6.3 Feature Description
      1. 6.3.1 Enable/Shutdown
      2. 6.3.2 Power Good
      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 Adjusting the Output Voltage
      2. 7.1.2 Input, Output, and Bias Capacitor Requirements
      3. 7.1.3 Transient Response
      4. 7.1.4 Dropout Voltage
      5. 7.1.5 Output Noise
    2. 7.2 Typical Applications
      1. 7.2.1 FPGA I/O Supply at 1.5 V With a Bias Rail
        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 FPGA I/O Supply at 1.5 V Without a Bias Rail
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Estimating Junction Temperature
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Device Nomenclature
      2. 8.1.2 Development Support
        1. 8.1.2.1 Evaluation Modules
        2. 8.1.2.2 Spice Models
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 接收文档更新通知
    4. 8.4 支持资源
    5. 8.5 Trademarks
    6. 8.6 静电放电警告
    7. 8.7 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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7.1.5 Output Noise

The TPS748 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 1-nF 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 RMS noise with a 1-nF soft-start capacitor is given in Equation 5:

Equation 5. TPS748

The low output noise of the TPS748 makes the device a good choice for powering transceivers, PLLs, or other noise-sensitive circuitry.