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

9.3.2 Turn-On Time (tON) and Adjustable Slew Rate (CT)

A capacitor to VIN on the CT pin sets the slew rate of VOUT. The CT capacitor voltage ramps until shortly after the switch is turned on and VOUT becomes stable.

Leaving the CT pin open results in the highest slew rate and fastest turn-on time. These values can be found in the Switching Characteristics Table. For slower slew rates the required CT capacitor can be found using Equation 1:

Equation 1. CT = (Slew Rate) ÷ SRON

where

  • Slew Rate = desired slew rate (mV/us)
  • CT = the capacitance value on the CT pin (pF)
  • SRON = slew rate constant from table [(mV/µs) × pF]

The total turn-on time has a direct correlation to the output slew rate. The fastest turn on times (tON), with CT pin open, can be found in the Switching Characteristics. For slower slew rates, the resulting turn-on time can be found with Equation 2:

Equation 2. Turn-On time = CT × tON

where

  • Turn-On Time = total time from enable until VOUT rises to 90% of VIN (µs)
  • CT =the capacitance value on the CT pin (pF)
  • tON = Turn-On time constant (µs/pF)