SLVSDW8B September   2017  – December 2021 TPS22917

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 Switching Characteristics
    7. 7.7 Typical Characteristics
      1. 7.7.1 Typical Electrical Characteristics
      2. 7.7.2 Typical Switching Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Test Circuit and Timing Waveforms Diagrams
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 On and Off Control
      2. 9.3.2 Turn-On Time (tON) and Adjustable Slew Rate (CT)
      3. 9.3.3 Fall Time (tFALL) and Quick Output Discharge (QOD)
        1. 9.3.3.1 QOD When System Power is Removed
    4. 9.4 Full-Time Reverse Current Blocking
    5. 9.5 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Limiting Inrush Current
        2. 10.2.2.2 Application Curves
        3. 10.2.2.3 Setting Fall Time for Shutdown Power Sequencing
        4. 10.2.2.4 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Considerations
  13. 13Device and Documentation Support
    1. 13.1 Receiving Notification of Documentation Updates
    2. 13.2 Support Resources
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.3.3 Fall Time (tFALL) and Quick Output Discharge (QOD)

The TPS22917x device includes a QOD pin that can be configured in one of three ways:

  • QOD pin shorted to VOUT pin. Using this method, the discharge rate after the switch becomes disabled is controlled with the value of the internal resistance QOD.
  • QOD pin connected to VOUT pin using an external resistor RQOD. After the switch becomes disabled, the discharge rate is controlled by the value of the total discharge resistance. To adjust the total discharge resistance, Equation 3 can be used:
    Equation 3. RDIS = QOD + RQOD

    • Where:

    • RDIS = total output discharge resistance (Ω)
    • QOD = internal pulldown resistance (Ω)
    • RQOD = external resistance placed between the VOUT and QOD pins (Ω)
  • QOD pin is unused and left floating. Using this method, there is no quick output discharge functionality, and the output remains floating after the switch is disabled.

The fall times of the device depend on many factors including the total discharge resistance (RDIS) and the output capacitance (CL). To calculate the approximate fall time of VOUT use Equation 4.

Equation 4. tFALL = 2.2 × (RDIS || RL) × CL

Where:

  • tFALL = output fall time from 90% to 10% (μs)
  • RDIS = total QOD + RQOD resistance (Ω)
  • RL = output load resistance (Ω)
  • CL = output load capacitance (μF)