SLVSEN5B October   2018  – May 2019 TPS22919

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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
  7. 7 Parameter Measurement Information
    1. 7.1 Test Circuit and Timing Waveforms Diagrams
  8. 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 Output Short Circuit Protection (ISC)
      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 Device Functional Modes
  9. 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 Setting Fall Time for Shutdown Power Sequencing
        3. 9.2.2.3 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

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

The TPS22919 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 (RPD,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 1 can be used:
    • Equation 1. RDIS = RPD,QOD + RQOD

    where

    • RDIS = Total output discharge resistance (Ω)
    • RPD,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 will be no quick output discharge functionality, and the output will remain 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 2.

Equation 2. 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)