SLVSDW8A September   2017  – February 2018 TPS22917

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simplified Schematic
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin Functions
  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 Switching Characteristics
    7. 6.7 Typical Characteristics
      1. 6.7.1 Typical Electrical Characteristics
      2. 6.7.2 Typical Switching Characteristics
  7. Parameter Measurement Information
    1. 7.1 Test Circuit and Timing Waveforms Diagrams
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 On and Off Control
      2. 8.3.2 Turn On Time (tON) and Adjustable Slew Rate (CT)
      3. 8.3.3 Fall Time (tFALL) and Quick Output Discharge (QOD)
        1. 8.3.3.1 QOD when System Power is Removed
    4. 8.4 Full-Time Reverse Current Blocking
    5. 8.5 Device Functional Modes
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Limiting Inrush Current
        2. 9.2.2.2 Application Curves
        3. 9.2.2.3 Setting Fall Time for Shutdown Power Sequencing
        4. 9.2.2.4 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Setting Fall Time for Shutdown Power Sequencing

Microcontrollers and processors often have a specific shutdown sequence in which power must be removed. Using the adjustable Quick Output Discharge function of the TPS22917, adding a load switch to each power rail can be used to manage the power down sequencing. To determine the QOD values for each load switch, first confirm the power down order of the device you wish to power sequence. Be sure to check if there are voltage or timing margins that must be maintained during power down.

Once the required fall time is determined, the maximum external discharge resistance (RDIS) value can be found using Equation 4:

Equation 8. tFALL = 2.2 × (RDIS || RL) × CL
Equation 9. RDIS = 630 Ω

Equation 3 can then be used to calculate the RQOD resistance needed to acheive a particular discharge value:

Equation 10. RDIS = QOD + RQOD
Equation 11. RQOD = 480 Ω

To ensure a fall time greater than, choose an RQOD value greater than 480 Ω.