SLVSFX8A March   2021  – March 2022 TPS2521

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
      1.      15
    8. 7.8 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Reverse Polarity Protection
      2. 8.3.2 Undervoltage Lockout (UVLO and UVP)
      3. 8.3.3 Overvoltage Clamp (OVC)
      4. 8.3.4 Inrush Current, Overcurrent, and Short Circuit Protection
        1. 8.3.4.1 Slew Rate (dVdt) and Inrush Current Control
        2. 8.3.4.2 Active Current Limiting
        3. 8.3.4.3 Short-Circuit Protection
      5. 8.3.5 Analog Load Current Monitor
      6. 8.3.6 Reverse Current Protection
      7. 8.3.7 Overtemperature Protection (OTP)
      8. 8.3.8 Fault Response
      9. 8.3.9 Power Good Indication (PG)
    4. 8.4 Device Functional Modes
  9. 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 Application
      2. 9.3.2 Design Requirements
      3. 9.3.3 Detailed Design Procedure
        1. 9.3.3.1 Device Selection
        2. 9.3.3.2 Setting Undervoltage and Overvoltage Thresholds
        3. 9.3.3.3 Setting Output Voltage Rise Time (tR)
        4. 9.3.3.4 Setting Power Good Assertion Threshold
        5. 9.3.3.5 Setting Overcurrent Threshold (ILIM)
        6. 9.3.3.6 Setting Overcurrent Blanking Interval (tITIMER)
      4. 9.3.4 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Transient Protection
    2. 10.2 Output Short-Circuit Measurements
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.3.3.4 Setting Power Good Assertion Threshold

The Power Good assertion threshold can be set using the resistors R3 and R4 connected to the PGTH pin whose values can be calculated as:

Equation 12. GUID-20210329-CA0I-KSMJ-CVLH-J7RCGHV6GSNF-low.gif
Because R3 and R4 leak the current from the output rail VOUT, these resistors must be selected to minimize the leakage current. The current drawn by R3and R4 from the power supply is IR34 = VOUT / (R3 + R4). However, leakage currents due to external active components connected to the resistor string can add error to these calculations. So, the resistor string current, IR34 must be chosen to be 20 times greater than the PGTH leakage current expected. From the device electrical specifications, PGTH leakage current is 1 μA (maximum), VPGTH(R) = 1.2 V and from design requirements, VPG = 4.5 V. To solve the equation, first choose the value of R3 = 100 kΩ and calculate R4 = 36.4 kΩ. Choose nearest 1% standard resistor value as R4 = 36.5 kΩ.