ZHCSQ77A February   2023  – September 2023 TPS25948

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Electrical Characteristics
    5. 7.5 Timing Requirements
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Undervoltage Lockout (UVLO and UVP)
      2. 8.3.2 Overvoltage Lockout (OVLO)
      3. 8.3.3 Inrush Current, Overcurrent, and Short Circuit Protection
        1. 8.3.3.1 Slew Rate (dVdt) and Inrush Current Control
        2. 8.3.3.2 Active Current Limiting
        3. 8.3.3.3 Short-Circuit Protection
      4. 8.3.4 Analog Load Current Monitor
      5. 8.3.5 Reverse Current Protection
      6. 8.3.6 Overtemperature Protection (OTP)
      7. 8.3.7 Fault Response and Indication (FLT)
      8. 8.3.8 Supply Good Indication (SPLYGD/SPLYGD)
    4. 8.4 Device Functional Modes
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Single Device, Self-Controlled
    3. 9.3 Typical Application
      1. 9.3.1 Design Requirements
      2. 9.3.2 Detailed Design Procedure
        1. 9.3.2.1 Setting Overvoltage Threshold
        2. 9.3.2.2 Setting Output Voltage Rise Time (tR)
        3. 9.3.2.3 Setting Overcurrent Threshold (ILIM)
        4. 9.3.2.4 Setting Overcurrent Blanking Interval (tITIMER)
      3. 9.3.3 Application Curves
    4. 9.4 Active ORing
    5. 9.5 Priority Power MUXing
    6. 9.6 Parallel Operation
    7. 9.7 USB PD Port Protection
    8. 9.8 Power Supply Recommendations
      1. 9.8.1 Transient Protection
      2. 9.8.2 Output Short-Circuit Measurements
    9. 9.9 Layout
      1. 9.9.1 Layout Guidelines
      2. 9.9.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 接收文档更新通知
    3. 10.3 支持资源
    4. 10.4 Trademarks
    5. 10.5 静电放电警告
    6. 10.6 术语表
  12. 11Mechanical, Packaging, and Orderable Information

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9.3.2.1 Setting Overvoltage Threshold

The supply overvoltage threshold is set using the resistors, R1 and R2, whose values can be calculated as:
Equation 8. VIN(OV)=VOV(R) x (R1 + R2)R2 
Where VOV(R) is the OVLO rising threshold. Because R1, R2 leak the current from input supply VIN, these resistors must be selected based on the acceptable leakage current from input power supply VIN. The current drawn by R1, R2 from the power supply is IR12 = VIN / (R1 + R2). However, leakage currents due to external active components connected to the resistor string can add error to these calculations. So, the resistor string current, IR12, must be chosen to be 20 times greater than the leakage current expected on the OVLO pin.

From the device electrical specifications, OVLO leakage current is 0.1 μA (maximum), VOV(R) = 1.2 V. From design requirements, VIN(OV) = 22 V. To solve the equation, first choose the value of R1 = 470 kΩ and use the above equation to solve for R2 = 27.11 kΩ.

Using the closest standard 1% resistor values, we get R1 = 470 kΩ, R2 = 26.7 kΩ.