SLVSG05A October   2021  – December 2021 TPS22998

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 (VBIAS = 5 V)
    6. 6.6  Electrical Characteristics (VBIAS = 3.3 V)
    7. 6.7  Electrical Characteristics (VBIAS = 2.2 V)
    8. 6.8  Switching Characteristics (VBIAS = 2.2 V to 5 V)
    9. 6.9  Timing Diagram
    10. 6.10 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 ON and OFF Control
      2. 7.3.2 Adjustable Slew Rate
      3. 7.3.3 Thermal Shutdown
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Performance Plots
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2 Detailed Design Procedure

When the switch enables, the charge up the output capacitance from 0 V to the set value (1.8 V in this example). This charge arrives in the form of inrush current. Calculate inrush current using Equation 1.

Equation 1. Inrush Current = CL × dVOUT/dt

Where:

  • CL is the output capacitance.
  • dVOUT is the change in VOUT during the ramp up of the output voltage when device is enabled. Because rise time is 10% of VOUT to 90% of VOUT, this is 80% of the VIN value.
  • dt is the rise time in VOUT during the ramp up of the output voltage when the device is enabled.

The TPS22998 offers an adjustable rise time for VOUT, allowing the user to control the inrush current during turn on. Calculate the appropriate rise time using the design requirements and the inrush current equation as shown below.

Equation 2. 1A = 470 µF × (1.8 V × 80%) / dt
Equation 3. dt = 677µs

To ensure an inrush current of less than 1 A, a CT setting that yields a rise time of more than 677 µs must be chosen. By pulling the CT pin high, a rise time of 900 μs is selected, limiting the inrush current to below 1 A.