SLVSCG3F January   2014  – July 2017 TPS22968

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Schematic
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1.     Pin 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 (VBIAS = 5 V)
    6. 7.6 Electrical Characteristics (VBIAS = 2.5 V)
    7. 7.7 Switching Characteristics
    8. 7.8 Typical DC Characteristics
    9. 7.9 Typical AC Characteristics
  8. 8 Parameter Measurement Information
  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 Input Capacitor (Optional)
      3. 9.3.3 Output Capacitor (Optional)
      4. 9.3.4 QOD (Optional)
      5. 9.3.5 VIN and VBIAS Voltage Range
      6. 9.3.6 Adjustable Rise Time
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Parallel Configuration
      2. 10.1.2 Standby Power Reduction
      3. 10.1.3 Power Supply Sequencing Without a GPIO Input
      4. 10.1.4 Reverse Current Blocking
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 VIN to VOUT Voltage Drop
        2. 10.2.2.2 Inrush Current
        3. 10.2.2.3 Thermal Considerations
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Development Support
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Related Links
    4. 13.4 Receiving Notification of Documentation Updates
    5. 13.5 Community Resources
    6. 13.6 Trademarks
    7. 13.7 Electrostatic Discharge Caution
    8. 13.8 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.2.2 Inrush Current

To determine how much inrush current is caused by the CL capacitor, use Equation 3.

Equation 3. TPS22968 TPS22968N Eq2_Iinrush_slvsci4.gif

where

  • IINRUSH is the amount of inrush caused by CL
  • CL is the capacitance on VOUT
  • dt is the time it takes for change in VOUT during the ramp up of VOUT when the device is enabled
  • dVOUT is the change in VOUT during the ramp up of VOUT when the device is enabled

The device offers adjustable rise time for VOUT. This feature allows the user to control the inrush current during turnon through the CTx pins. The appropriate rise time can be calculated using the design requirements and the inrush current equation ( Equation 3). See Equation 4 and Equation 5.

Equation 4. 330 mA = 22 µF × 3.3 V / dt
Equation 5. dt = 220 µs

To ensure an inrush current of less than 330 mA, choose a CT based on Table 1 or Equation 1 value that yields a rise time of more than 220 µs. See the oscilloscope captures in the Application Curves for an example of how the CT capacitor can be used to reduce inrush current. See Table 1 for correlation between rise times and CT values.

An appropriate CL value must be placed on VOUT such that the IMAX and IPLS specifications of the device are not violated.