SLVSGT9B February   2023  – June 2024 TPS25948

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Undervoltage Lockout (UVLO and UVP)
      2. 7.3.2 Overvoltage Lockout (OVLO)
      3. 7.3.3 Inrush Current, Overcurrent, and Short Circuit Protection
        1. 7.3.3.1 Slew Rate (dVdt) and Inrush Current Control
        2. 7.3.3.2 Active Current Limiting
        3. 7.3.3.3 Short-Circuit Protection
      4. 7.3.4 Analog Load Current Monitor
      5. 7.3.5 Reverse Current Protection
      6. 7.3.6 Overtemperature Protection (OTP)
      7. 7.3.7 Fault Response and Indication (FLT)
      8. 7.3.8 Supply Good Indication (SPLYGD/SPLYGD)
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Single Device, Self-Controlled
    3. 8.3 Typical Application
      1. 8.3.1 Design Requirements
      2. 8.3.2 Detailed Design Procedure
        1. 8.3.2.1 Setting Overvoltage Threshold
        2. 8.3.2.2 Setting Output Voltage Rise Time (tR)
        3. 8.3.2.3 Setting Overcurrent Threshold (ILIM)
        4. 8.3.2.4 Setting Overcurrent Blanking Interval (tITIMER)
      3. 8.3.3 Application Curves
    4. 8.4 Active ORing
    5. 8.5 Priority Power MUXing
    6. 8.6 Parallel Operation
    7. 8.7 USB PD Port Protection
    8. 8.8 Power Supply Recommendations
      1. 8.8.1 Transient Protection
      2. 8.8.2 Output Short-Circuit Measurements
    9. 8.9 Layout
      1. 8.9.1 Layout Guidelines
      2. 8.9.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.3.1 Slew Rate (dVdt) and Inrush Current Control

During hot-plug events or while trying to charge a large output capacitance at start-up, there can be a large inrush current. If the inrush current is not managed properly, it can damage the input connectors and/or cause the system power supply to droop leading to unexpected restarts elsewhere in the system. The inrush current during turn on is directly proportional to the load capacitance and rising slew rate.

Equation 3 can be used to find the slew rate (SR) required to limit the inrush current (IINRUSH) for a given load capacitance (COUT):

Equation 3. IINRUSH (mA) = COUT (µF) × SRON (V/ms)

A capacitor can be connected to the dVdt pin to control the rising slew rate and lower the inrush current during turn on. The required CdVdt capacitance to produce a given slew rate can be calculated using the equation:

Equation 4. CDVDT (pF) = 5000SRON (V/ms)

The fastest output slew rate is achieved by leaving the dVdt pin open.

Note:
  1. The slew rate calculation above holds good for CdVdt > 1 nF. For lower CdVdt values, the internal gate capacitance may dominate and cause the actual slew rate to deviate from the calculation.
  2. Slew rate control during start-up is provided only on the HFET which enables inrush current control from IN to OUT.
  3. For CdVdt > 10 nF, it is recommended to add a 100-Ω resistor in series with the capacitor on the dVdt pin.