ZHCSSM4E August   1999  – March 2024 TPS766

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 (Legacy Chip)
    5. 5.5 Thermal Information (New Chip)
    6. 5.6 Electrical Characteristics
    7. 5.7 Timing Diagram
    8. 5.8 Typical Characteristics
    9. 5.9 Typical Characteristics: Supported ESR Range
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagrams
    3. 6.3 Feature Description
      1. 6.3.1 Output Enable
      2. 6.3.2 Dropout Voltage
      3. 6.3.3 Current Limit
      4. 6.3.4 Undervoltage Lockout (UVLO)
      5. 6.3.5 Power-Good Function
      6. 6.3.6 Output Pulldown
      7. 6.3.7 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Device Functional Mode Comparison
      2. 6.4.2 Normal Operation
      3. 6.4.3 Dropout Operation
      4. 6.4.4 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 Adjustable Device Feedback Resistors
        2. 7.2.2.2 Recommended Capacitor Types
        3. 7.2.2.3 Input and Output Capacitor Requirements
        4. 7.2.2.4 Reverse Current
        5. 7.2.2.5 Feed-Forward Capacitor (CFF)
        6. 7.2.2.6 Power Dissipation (PD)
        7. 7.2.2.7 Estimating Junction Temperature
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 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

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
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散热焊盘机械数据 (封装 | 引脚)
订购信息

7.2.2.5 Feed-Forward Capacitor (CFF)

For the adjustable-voltage version device, connect a feed-forward capacitor (CFF) from the OUT pin to the FB pin. CFF improves transient, noise, and PSRR performance, but is not required for regulator stability. Recommended CFF values are listed in the Recommended Operating Conditions table. If a higher capacitance CFF is used, the start-up time increases. For a detailed description of CFF tradeoffs, see the Pros and Cons of Using a Feedforward Capacitor with a Low-Dropout Regulator application note.

CFF and R1 form a zero in the loop gain at frequency fZ, while CFF, R1, and R2 form a pole in the loop gain at frequency fP. Calculate the CFF zero and pole frequencies from the following equations:

Equation 4. fZ = 1 / (2 × π × CFF × R1)
Equation 5. fP = 1 / (2 × π × CFF × (R1 || R2))

CFF ≥ 10pF is required for stability if the feedback divider current is less than 5μA. The following equation calculates the feedback divider current.

Equation 6. IFB_Divider = VOUT / (R1 + R2)

To avoid start-up time increases from CFF, limit the product CFF × R1 < 50µs.

For an output voltage of 1.224V with the FB pin tied to the OUT pin, no CFF is used.