SLVS850A June   2008  – September 2023 TPS2551-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configurations and Functions
  7. 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 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Overcurrent
      2. 8.3.2 Reverse-Voltage Protection
      3. 8.3.3 FAULT Response
      4. 8.3.4 Undervoltage Lockout (UVLO)
      5. 8.3.5 Enable (EN)
      6. 8.3.6 Thermal Sense
      7. 8.3.7 Device Functional Modes
    4. 8.4 Programming
      1. 8.4.1 Programming the Current-Limit Threshold
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Two-Level Current-Limit Circuit
      2. 9.2.2 Design Requirements
      3. 9.2.3 Detail Design Procedure
        1. 9.2.3.1 Designing Above a Minimum Current Limit
        2. 9.2.3.2 Designing Below a Maximum Current Limit
        3. 9.2.3.3 Input and Output Capacitance
      4. 9.2.4 Auto-Retry Functionality
      5. 9.2.5 Latch-Off Functionality
      6. 9.2.6 Typical Application as USB Power Switch
        1. 9.2.6.1 Design Requirements
          1. 9.2.6.1.1 USB Power-Distribution Requirements
        2. 9.2.6.2 Detail Design Procedure
          1. 9.2.6.2.1 Universal Serial Bus (USB) Power-Distribution Requirements
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Self-Powered and Bus-Powered Hubs
      2. 9.3.2 Low-Power Bus-Powered and High-Power Bus-Powered Functions
      3. 9.3.3 Power Dissipation and Junction Temperature
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Receiving Notification of Documentation Updates
    2. 10.2 Support Resources
    3. 10.3 Trademarks
    4. 10.4 Electrostatic Discharge Caution
    5. 10.5 Glossary
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.3.2 Designing Below a Maximum Current Limit

Some applications require that current-limiting must occur below a certain threshold. For this example, assume that the desired upper current-limit threshold must be below 1.25 A to protect an up-stream power supply. Use the IOC equations and Figure 8-1 to select RILIM.

  • IOC(max) (mA) = 1250 mA
  • IOC(max) (mA) = (24500 V) / (RILIM (kΩ))0.975 + 50
  • RILIM (kΩ) = [(24500 V) / ((IOC(max) (mA)) - 50)]1/0.975
  • RILIM = 22.05 kΩ

Select the closest 1% resistor greater than the calculated value: RILIM = 22 kΩ. This selection sets the maximum current-limit threshold at 1.25 A. Use the IOS equations, Figure 8-1, and the previously calculated value for RILIM to calculate the minimum resulting current-limit threshold.

  • RILIM = 22 kΩ
  • IOS(min) (mA) = (39700 V) / (RILIM (kΩ)) 1.342 + 50
  • IOS(min) (mA) = (39700 V) / (22 (kΩ)) 1.342 + 50
  • IOS(min) = 677 mA

The resulting minimum current-limit threshold is 677 mA with a 22-kΩ resistor.