SLVSDT3D January   2018  – December 2019 TPS25221

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Device Comparison Table
  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
    6. 7.6 Typical 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 Over-current Conditions
      2. 9.3.2 Fault Response
      3. 9.3.3 Undervoltage Lockout (UVLO)
      4. 9.3.4 Enable, (EN)
      5. 9.3.5 Thermal Sense
    4. 9.4 Device Functional Modes
    5. 9.5 Programming
      1. 9.5.1 Programming the Current-Limit Threshold
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Constant-Current
    2. 10.2 Typical Applications
      1. 10.2.1 Two-Level Current-Limit Circuit
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedures
          1. 10.2.1.2.1 Designing Above a Minimum Current Limit
          2. 10.2.1.2.2 Designing Below a Maximum Current Limit
          3. 10.2.1.2.3 Accounting for Resistor Tolerance
          4. 10.2.1.2.4 Input and Output Capacitance
        3. 10.2.1.3 Application Curve
      2. 10.2.2 Auto-Retry Functionality
        1. 10.2.2.1 Design Requirements (added)
        2. 10.2.2.2 Detailed Design Procedure
      3. 10.2.3 Typical Application as USB Power Switch
        1. 10.2.3.1 Design Requirements
          1. 10.2.3.1.1 USB Power-Distribution Requirements
        2. 10.2.3.2 Detailed Design Procedure
          1. 10.2.3.2.1 Universal Serial Bus (USB) Power-Distribution Requirements
  11. 11Power Supply Recommendations
    1. 11.1 Self-Powered and Bus-Powered Hubs
    2. 11.2 Low-Power Bus-Powered and High-Power Bus-Powered Functions
    3. 11.3 Power Dissipation and Junction Temperature
  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 Third-Party Products Disclaimer
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

10.1.1 Constant-Current

During normal operation, the TPS25221 load current is less than the current-limit threshold and the device is not limiting current. During normal operation the N-channel MOSFET is fully enhanced, and VOUT = VIN - (IOUT x rDS(on)). The voltage drop across the MOSFET is relatively small compared to VIN, and VOUT is approximately equal to VIN.

The TPS25221 limits current to the programmed current-limit threshold, set by RILIM, reducing gate drive to the internal NFET, which increases Rds(on) and reduces load current. This allows the device to effectively regulate the current to the current-limit threshold. Increasing the resistance of the MOSFET means that the voltage drop across the device is no longer negligible (VIN ≠ VOUT), and VOUT decreases. The amount that VOUT decreases is proportional to the magnitude of the overload condition. The expected VOUT can be calculated by:

Equation 2. IOS × RLOAD

where

    For example, if IOS is programmed to 1 A and a 1 Ω overload condition is applied, the resulting VOUT is 1 V.

    While in current limit the power dissipation in the package can raise the die temperature above the thermal shutdown threshold (145°C typical), and the device turns off until the die temperature decreases by the hysteresis of the thermal shutdown circuit (20°C typical). The device then turns on and continues to thermal cycle until the overload condition is removed.